Bootlin logo

Elixir Cross Referencer

   1
   2
   3
   4
   5
   6
   7
   8
   9
  10
  11
  12
  13
  14
  15
  16
  17
  18
  19
  20
  21
  22
  23
  24
  25
  26
  27
  28
  29
  30
  31
  32
  33
  34
  35
  36
  37
  38
  39
  40
  41
  42
  43
  44
  45
  46
  47
  48
  49
  50
  51
  52
  53
  54
  55
  56
  57
  58
  59
  60
  61
  62
  63
  64
  65
  66
  67
  68
  69
  70
  71
  72
  73
  74
  75
  76
  77
  78
  79
  80
  81
  82
  83
  84
  85
  86
  87
  88
  89
  90
  91
  92
  93
  94
  95
  96
  97
  98
  99
 100
 101
 102
 103
 104
 105
 106
 107
 108
 109
 110
 111
 112
 113
 114
 115
 116
 117
 118
 119
 120
 121
 122
 123
 124
 125
 126
 127
 128
 129
 130
 131
 132
 133
 134
 135
 136
 137
 138
 139
 140
 141
 142
 143
 144
 145
 146
 147
 148
 149
 150
 151
 152
 153
 154
 155
 156
 157
 158
 159
 160
 161
 162
 163
 164
 165
 166
 167
 168
 169
 170
 171
 172
 173
 174
 175
 176
 177
 178
 179
 180
 181
 182
 183
 184
 185
 186
 187
 188
 189
 190
 191
 192
 193
 194
 195
 196
 197
 198
 199
 200
 201
 202
 203
 204
 205
 206
 207
 208
 209
 210
 211
 212
 213
 214
 215
 216
 217
 218
 219
 220
 221
 222
 223
 224
 225
 226
 227
 228
 229
 230
 231
 232
 233
 234
 235
 236
 237
 238
 239
 240
 241
 242
 243
 244
 245
 246
 247
 248
 249
 250
 251
 252
 253
 254
 255
 256
 257
 258
 259
 260
 261
 262
 263
 264
 265
 266
 267
 268
 269
 270
 271
 272
 273
 274
 275
 276
 277
 278
 279
 280
 281
 282
 283
 284
 285
 286
 287
 288
 289
 290
 291
 292
 293
 294
 295
 296
 297
 298
 299
 300
 301
 302
 303
 304
 305
 306
 307
 308
 309
 310
 311
 312
 313
 314
 315
 316
 317
 318
 319
 320
 321
 322
 323
 324
 325
 326
 327
 328
 329
 330
 331
 332
 333
 334
 335
 336
 337
 338
 339
 340
 341
 342
 343
 344
 345
 346
 347
 348
 349
 350
 351
 352
 353
 354
 355
 356
 357
 358
 359
 360
 361
 362
 363
 364
 365
 366
 367
 368
 369
 370
 371
 372
 373
 374
 375
 376
 377
 378
 379
 380
 381
 382
 383
 384
 385
 386
 387
 388
 389
 390
 391
 392
 393
 394
 395
 396
 397
 398
 399
 400
 401
 402
 403
 404
 405
 406
 407
 408
 409
 410
 411
 412
 413
 414
 415
 416
 417
 418
 419
 420
 421
 422
 423
 424
 425
 426
 427
 428
 429
 430
 431
 432
 433
 434
 435
 436
 437
 438
 439
 440
 441
 442
 443
 444
 445
 446
 447
 448
 449
 450
 451
 452
 453
 454
 455
 456
 457
 458
 459
 460
 461
 462
 463
 464
 465
 466
 467
 468
 469
 470
 471
 472
 473
 474
 475
 476
 477
 478
 479
 480
 481
 482
 483
 484
 485
 486
 487
 488
 489
 490
 491
 492
 493
 494
 495
 496
 497
 498
 499
 500
 501
 502
 503
 504
 505
 506
 507
 508
 509
 510
 511
 512
 513
 514
 515
 516
 517
 518
 519
 520
 521
 522
 523
 524
 525
 526
 527
 528
 529
 530
 531
 532
 533
 534
 535
 536
 537
 538
 539
 540
 541
 542
 543
 544
 545
 546
 547
 548
 549
 550
 551
 552
 553
 554
 555
 556
 557
 558
 559
 560
 561
 562
 563
 564
 565
 566
 567
 568
 569
 570
 571
 572
 573
 574
 575
 576
 577
 578
 579
 580
 581
 582
 583
 584
 585
 586
 587
 588
 589
 590
 591
 592
 593
 594
 595
 596
 597
 598
 599
 600
 601
 602
 603
 604
 605
 606
 607
 608
 609
 610
 611
 612
 613
 614
 615
 616
 617
 618
 619
 620
 621
 622
 623
 624
 625
 626
 627
 628
 629
 630
 631
 632
 633
 634
 635
 636
 637
 638
 639
 640
 641
 642
 643
 644
 645
 646
 647
 648
 649
 650
 651
 652
 653
 654
 655
 656
 657
 658
 659
 660
 661
 662
 663
 664
 665
 666
 667
 668
 669
 670
 671
 672
 673
 674
 675
 676
 677
 678
 679
 680
 681
 682
 683
 684
 685
 686
 687
 688
 689
 690
 691
 692
 693
 694
 695
 696
 697
 698
 699
 700
 701
 702
 703
 704
 705
 706
 707
 708
 709
 710
 711
 712
 713
 714
 715
 716
 717
 718
 719
 720
 721
 722
 723
 724
 725
 726
 727
 728
 729
 730
 731
 732
 733
 734
 735
 736
 737
 738
 739
 740
 741
 742
 743
 744
 745
 746
 747
 748
 749
 750
 751
 752
 753
 754
 755
 756
 757
 758
 759
 760
 761
 762
 763
 764
 765
 766
 767
 768
 769
 770
 771
 772
 773
 774
 775
 776
 777
 778
 779
 780
 781
 782
 783
 784
 785
 786
 787
 788
 789
 790
 791
 792
 793
 794
 795
 796
 797
 798
 799
 800
 801
 802
 803
 804
 805
 806
 807
 808
 809
 810
 811
 812
 813
 814
 815
 816
 817
 818
 819
 820
 821
 822
 823
 824
 825
 826
 827
 828
 829
 830
 831
 832
 833
 834
 835
 836
 837
 838
 839
 840
 841
 842
 843
 844
 845
 846
 847
 848
 849
 850
 851
 852
 853
 854
 855
 856
 857
 858
 859
 860
 861
 862
 863
 864
 865
 866
 867
 868
 869
 870
 871
 872
 873
 874
 875
 876
 877
 878
 879
 880
 881
 882
 883
 884
 885
 886
 887
 888
 889
 890
 891
 892
 893
 894
 895
 896
 897
 898
 899
 900
 901
 902
 903
 904
 905
 906
 907
 908
 909
 910
 911
 912
 913
 914
 915
 916
 917
 918
 919
 920
 921
 922
 923
 924
 925
 926
 927
 928
 929
 930
 931
 932
 933
 934
 935
 936
 937
 938
 939
 940
 941
 942
 943
 944
 945
 946
 947
 948
 949
 950
 951
 952
 953
 954
 955
 956
 957
 958
 959
 960
 961
 962
 963
 964
 965
 966
 967
 968
 969
 970
 971
 972
 973
 974
 975
 976
 977
 978
 979
 980
 981
 982
 983
 984
 985
 986
 987
 988
 989
 990
 991
 992
 993
 994
 995
 996
 997
 998
 999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
/*
 * random.c -- A strong random number generator
 *
 * Version 1.89, last modified 19-Sep-99
 *
 * Copyright Theodore Ts'o, 1994, 1995, 1996, 1997, 1998, 1999.  All
 * rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, and the entire permission notice in its entirety,
 *    including the disclaimer of warranties.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote
 *    products derived from this software without specific prior
 *    written permission.
 *
 * ALTERNATIVELY, this product may be distributed under the terms of
 * the GNU General Public License, in which case the provisions of the GPL are
 * required INSTEAD OF the above restrictions.  (This clause is
 * necessary due to a potential bad interaction between the GPL and
 * the restrictions contained in a BSD-style copyright.)
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF
 * WHICH ARE HEREBY DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
 * USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH
 * DAMAGE.
 */

/*
 * (now, with legal B.S. out of the way.....)
 *
 * This routine gathers environmental noise from device drivers, etc.,
 * and returns good random numbers, suitable for cryptographic use.
 * Besides the obvious cryptographic uses, these numbers are also good
 * for seeding TCP sequence numbers, and other places where it is
 * desirable to have numbers which are not only random, but hard to
 * predict by an attacker.
 *
 * Theory of operation
 * ===================
 *
 * Computers are very predictable devices.  Hence it is extremely hard
 * to produce truly random numbers on a computer --- as opposed to
 * pseudo-random numbers, which can easily generated by using a
 * algorithm.  Unfortunately, it is very easy for attackers to guess
 * the sequence of pseudo-random number generators, and for some
 * applications this is not acceptable.  So instead, we must try to
 * gather "environmental noise" from the computer's environment, which
 * must be hard for outside attackers to observe, and use that to
 * generate random numbers.  In a Unix environment, this is best done
 * from inside the kernel.
 *
 * Sources of randomness from the environment include inter-keyboard
 * timings, inter-interrupt timings from some interrupts, and other
 * events which are both (a) non-deterministic and (b) hard for an
 * outside observer to measure.  Randomness from these sources are
 * added to an "entropy pool", which is mixed using a CRC-like function.
 * This is not cryptographically strong, but it is adequate assuming
 * the randomness is not chosen maliciously, and it is fast enough that
 * the overhead of doing it on every interrupt is very reasonable.
 * As random bytes are mixed into the entropy pool, the routines keep
 * an *estimate* of how many bits of randomness have been stored into
 * the random number generator's internal state.
 *
 * When random bytes are desired, they are obtained by taking the SHA
 * hash of the contents of the "entropy pool".  The SHA hash avoids
 * exposing the internal state of the entropy pool.  It is believed to
 * be computationally infeasible to derive any useful information
 * about the input of SHA from its output.  Even if it is possible to
 * analyze SHA in some clever way, as long as the amount of data
 * returned from the generator is less than the inherent entropy in
 * the pool, the output data is totally unpredictable.  For this
 * reason, the routine decreases its internal estimate of how many
 * bits of "true randomness" are contained in the entropy pool as it
 * outputs random numbers.
 *
 * If this estimate goes to zero, the routine can still generate
 * random numbers; however, an attacker may (at least in theory) be
 * able to infer the future output of the generator from prior
 * outputs.  This requires successful cryptanalysis of SHA, which is
 * not believed to be feasible, but there is a remote possibility.
 * Nonetheless, these numbers should be useful for the vast majority
 * of purposes.
 *
 * Exported interfaces ---- output
 * ===============================
 *
 * There are three exported interfaces; the first is one designed to
 * be used from within the kernel:
 *
 * 	void get_random_bytes(void *buf, int nbytes);
 *
 * This interface will return the requested number of random bytes,
 * and place it in the requested buffer.
 *
 * The two other interfaces are two character devices /dev/random and
 * /dev/urandom.  /dev/random is suitable for use when very high
 * quality randomness is desired (for example, for key generation or
 * one-time pads), as it will only return a maximum of the number of
 * bits of randomness (as estimated by the random number generator)
 * contained in the entropy pool.
 *
 * The /dev/urandom device does not have this limit, and will return
 * as many bytes as are requested.  As more and more random bytes are
 * requested without giving time for the entropy pool to recharge,
 * this will result in random numbers that are merely cryptographically
 * strong.  For many applications, however, this is acceptable.
 *
 * Exported interfaces ---- input
 * ==============================
 *
 * The current exported interfaces for gathering environmental noise
 * from the devices are:
 *
 * 	void add_input_randomness(unsigned int type, unsigned int code,
 *                                unsigned int value);
 * 	void add_interrupt_randomness(int irq);
 *
 * add_input_randomness() uses the input layer interrupt timing, as well as
 * the event type information from the hardware.
 *
 * add_interrupt_randomness() uses the inter-interrupt timing as random
 * inputs to the entropy pool.  Note that not all interrupts are good
 * sources of randomness!  For example, the timer interrupts is not a
 * good choice, because the periodicity of the interrupts is too
 * regular, and hence predictable to an attacker.  Disk interrupts are
 * a better measure, since the timing of the disk interrupts are more
 * unpredictable.
 *
 * All of these routines try to estimate how many bits of randomness a
 * particular randomness source.  They do this by keeping track of the
 * first and second order deltas of the event timings.
 *
 * Ensuring unpredictability at system startup
 * ============================================
 *
 * When any operating system starts up, it will go through a sequence
 * of actions that are fairly predictable by an adversary, especially
 * if the start-up does not involve interaction with a human operator.
 * This reduces the actual number of bits of unpredictability in the
 * entropy pool below the value in entropy_count.  In order to
 * counteract this effect, it helps to carry information in the
 * entropy pool across shut-downs and start-ups.  To do this, put the
 * following lines an appropriate script which is run during the boot
 * sequence:
 *
 *	echo "Initializing random number generator..."
 *	random_seed=/var/run/random-seed
 *	# Carry a random seed from start-up to start-up
 *	# Load and then save the whole entropy pool
 *	if [ -f $random_seed ]; then
 *		cat $random_seed >/dev/urandom
 *	else
 *		touch $random_seed
 *	fi
 *	chmod 600 $random_seed
 *	dd if=/dev/urandom of=$random_seed count=1 bs=512
 *
 * and the following lines in an appropriate script which is run as
 * the system is shutdown:
 *
 *	# Carry a random seed from shut-down to start-up
 *	# Save the whole entropy pool
 *	echo "Saving random seed..."
 *	random_seed=/var/run/random-seed
 *	touch $random_seed
 *	chmod 600 $random_seed
 *	dd if=/dev/urandom of=$random_seed count=1 bs=512
 *
 * For example, on most modern systems using the System V init
 * scripts, such code fragments would be found in
 * /etc/rc.d/init.d/random.  On older Linux systems, the correct script
 * location might be in /etc/rcb.d/rc.local or /etc/rc.d/rc.0.
 *
 * Effectively, these commands cause the contents of the entropy pool
 * to be saved at shut-down time and reloaded into the entropy pool at
 * start-up.  (The 'dd' in the addition to the bootup script is to
 * make sure that /etc/random-seed is different for every start-up,
 * even if the system crashes without executing rc.0.)  Even with
 * complete knowledge of the start-up activities, predicting the state
 * of the entropy pool requires knowledge of the previous history of
 * the system.
 *
 * Configuring the /dev/random driver under Linux
 * ==============================================
 *
 * The /dev/random driver under Linux uses minor numbers 8 and 9 of
 * the /dev/mem major number (#1).  So if your system does not have
 * /dev/random and /dev/urandom created already, they can be created
 * by using the commands:
 *
 * 	mknod /dev/random c 1 8
 * 	mknod /dev/urandom c 1 9
 *
 * Acknowledgements:
 * =================
 *
 * Ideas for constructing this random number generator were derived
 * from Pretty Good Privacy's random number generator, and from private
 * discussions with Phil Karn.  Colin Plumb provided a faster random
 * number generator, which speed up the mixing function of the entropy
 * pool, taken from PGPfone.  Dale Worley has also contributed many
 * useful ideas and suggestions to improve this driver.
 *
 * Any flaws in the design are solely my responsibility, and should
 * not be attributed to the Phil, Colin, or any of authors of PGP.
 *
 * The code for SHA transform was taken from Peter Gutmann's
 * implementation, which has been placed in the public domain.
 * The code for MD5 transform was taken from Colin Plumb's
 * implementation, which has been placed in the public domain.
 * The MD5 cryptographic checksum was devised by Ronald Rivest, and is
 * documented in RFC 1321, "The MD5 Message Digest Algorithm".
 *
 * Further background information on this topic may be obtained from
 * RFC 1750, "Randomness Recommendations for Security", by Donald
 * Eastlake, Steve Crocker, and Jeff Schiller.
 */

#include <linux/utsname.h>
#include <linux/config.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/major.h>
#include <linux/string.h>
#include <linux/fcntl.h>
#include <linux/slab.h>
#include <linux/random.h>
#include <linux/poll.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/workqueue.h>
#include <linux/genhd.h>
#include <linux/interrupt.h>
#include <linux/spinlock.h>
#include <linux/percpu.h>

#include <asm/processor.h>
#include <asm/uaccess.h>
#include <asm/irq.h>
#include <asm/io.h>

/*
 * Configuration information
 */
#define DEFAULT_POOL_SIZE 512
#define SECONDARY_POOL_SIZE 128
#define BATCH_ENTROPY_SIZE 256
#define USE_SHA

/*
 * The minimum number of bits of entropy before we wake up a read on
 * /dev/random.  Should be enough to do a significant reseed.
 */
static int random_read_wakeup_thresh = 64;

/*
 * If the entropy count falls under this number of bits, then we
 * should wake up processes which are selecting or polling on write
 * access to /dev/random.
 */
static int random_write_wakeup_thresh = 128;

/*
 * When the input pool goes over trickle_thresh, start dropping most
 * samples to avoid wasting CPU time and reduce lock contention.
 */

static int trickle_thresh = DEFAULT_POOL_SIZE * 7;

static DEFINE_PER_CPU(int, trickle_count) = 0;

/*
 * A pool of size .poolwords is stirred with a primitive polynomial
 * of degree .poolwords over GF(2).  The taps for various sizes are
 * defined below.  They are chosen to be evenly spaced (minimum RMS
 * distance from evenly spaced; the numbers in the comments are a
 * scaled squared error sum) except for the last tap, which is 1 to
 * get the twisting happening as fast as possible.
 */
static struct poolinfo {
	int poolwords;
	int tap1, tap2, tap3, tap4, tap5;
} poolinfo_table[] = {
	/* x^2048 + x^1638 + x^1231 + x^819 + x^411 + x + 1  -- 115 */
	{ 2048,	1638,	1231,	819,	411,	1 },

	/* x^1024 + x^817 + x^615 + x^412 + x^204 + x + 1 -- 290 */
	{ 1024,	817,	615,	412,	204,	1 },
#if 0				/* Alternate polynomial */
	/* x^1024 + x^819 + x^616 + x^410 + x^207 + x^2 + 1 -- 115 */
	{ 1024,	819,	616,	410,	207,	2 },
#endif

	/* x^512 + x^411 + x^308 + x^208 + x^104 + x + 1 -- 225 */
	{ 512,	411,	308,	208,	104,	1 },
#if 0				/* Alternates */
	/* x^512 + x^409 + x^307 + x^206 + x^102 + x^2 + 1 -- 95 */
	{ 512,	409,	307,	206,	102,	2 },
	/* x^512 + x^409 + x^309 + x^205 + x^103 + x^2 + 1 -- 95 */
	{ 512,	409,	309,	205,	103,	2 },
#endif

	/* x^256 + x^205 + x^155 + x^101 + x^52 + x + 1 -- 125 */
	{ 256,	205,	155,	101,	52,	1 },

	/* x^128 + x^103 + x^76 + x^51 +x^25 + x + 1 -- 105 */
	{ 128,	103,	76,	51,	25,	1 },
#if 0	/* Alternate polynomial */
	/* x^128 + x^103 + x^78 + x^51 + x^27 + x^2 + 1 -- 70 */
	{ 128,	103,	78,	51,	27,	2 },
#endif

	/* x^64 + x^52 + x^39 + x^26 + x^14 + x + 1 -- 15 */
	{ 64,	52,	39,	26,	14,	1 },

	/* x^32 + x^26 + x^20 + x^14 + x^7 + x + 1 -- 15 */
	{ 32,	26,	20,	14,	7,	1 },

	{ 0,	0,	0,	0,	0,	0 },
};

#define POOLBITS	poolwords*32
#define POOLBYTES	poolwords*4

/*
 * For the purposes of better mixing, we use the CRC-32 polynomial as
 * well to make a twisted Generalized Feedback Shift Reigster
 *
 * (See M. Matsumoto & Y. Kurita, 1992.  Twisted GFSR generators.  ACM
 * Transactions on Modeling and Computer Simulation 2(3):179-194.
 * Also see M. Matsumoto & Y. Kurita, 1994.  Twisted GFSR generators
 * II.  ACM Transactions on Mdeling and Computer Simulation 4:254-266)
 *
 * Thanks to Colin Plumb for suggesting this.
 *
 * We have not analyzed the resultant polynomial to prove it primitive;
 * in fact it almost certainly isn't.  Nonetheless, the irreducible factors
 * of a random large-degree polynomial over GF(2) are more than large enough
 * that periodicity is not a concern.
 *
 * The input hash is much less sensitive than the output hash.  All
 * that we want of it is that it be a good non-cryptographic hash;
 * i.e. it not produce collisions when fed "random" data of the sort
 * we expect to see.  As long as the pool state differs for different
 * inputs, we have preserved the input entropy and done a good job.
 * The fact that an intelligent attacker can construct inputs that
 * will produce controlled alterations to the pool's state is not
 * important because we don't consider such inputs to contribute any
 * randomness.  The only property we need with respect to them is that
 * the attacker can't increase his/her knowledge of the pool's state.
 * Since all additions are reversible (knowing the final state and the
 * input, you can reconstruct the initial state), if an attacker has
 * any uncertainty about the initial state, he/she can only shuffle
 * that uncertainty about, but never cause any collisions (which would
 * decrease the uncertainty).
 *
 * The chosen system lets the state of the pool be (essentially) the input
 * modulo the generator polymnomial.  Now, for random primitive polynomials,
 * this is a universal class of hash functions, meaning that the chance
 * of a collision is limited by the attacker's knowledge of the generator
 * polynomail, so if it is chosen at random, an attacker can never force
 * a collision.  Here, we use a fixed polynomial, but we *can* assume that
 * ###--> it is unknown to the processes generating the input entropy. <-###
 * Because of this important property, this is a good, collision-resistant
 * hash; hash collisions will occur no more often than chance.
 */

/*
 * Linux 2.2 compatibility
 */
#ifndef DECLARE_WAITQUEUE
#define DECLARE_WAITQUEUE(WAIT, PTR) struct wait_queue WAIT = { PTR, NULL }
#endif
#ifndef DECLARE_WAIT_QUEUE_HEAD
#define DECLARE_WAIT_QUEUE_HEAD(WAIT) struct wait_queue *WAIT
#endif

/*
 * Static global variables
 */
static struct entropy_store *random_state; /* The default global store */
static struct entropy_store *sec_random_state; /* secondary store */
static struct entropy_store *urandom_state; /* For urandom */
static DECLARE_WAIT_QUEUE_HEAD(random_read_wait);
static DECLARE_WAIT_QUEUE_HEAD(random_write_wait);

/*
 * Forward procedure declarations
 */
#ifdef CONFIG_SYSCTL
static void sysctl_init_random(struct entropy_store *random_state);
#endif

/*****************************************************************
 *
 * Utility functions, with some ASM defined functions for speed
 * purposes
 *
 *****************************************************************/

/*
 * Unfortunately, while the GCC optimizer for the i386 understands how
 * to optimize a static rotate left of x bits, it doesn't know how to
 * deal with a variable rotate of x bits.  So we use a bit of asm magic.
 */
#if (!defined (__i386__))
static inline __u32 rotate_left(int i, __u32 word)
{
	return (word << i) | (word >> (32 - i));
}
#else
static inline __u32 rotate_left(int i, __u32 word)
{
	__asm__("roll %%cl,%0"
		:"=r" (word)
		:"0" (word),"c" (i));
	return word;
}
#endif

/*
 * More asm magic....
 *
 * For entropy estimation, we need to do an integral base 2
 * logarithm.
 *
 * Note the "12bits" suffix - this is used for numbers between
 * 0 and 4095 only.  This allows a few shortcuts.
 */
#if 0	/* Slow but clear version */
static inline __u32 int_ln_12bits(__u32 word)
{
	__u32 nbits = 0;

	while (word >>= 1)
		nbits++;
	return nbits;
}
#else	/* Faster (more clever) version, courtesy Colin Plumb */
static inline __u32 int_ln_12bits(__u32 word)
{
	/* Smear msbit right to make an n-bit mask */
	word |= word >> 8;
	word |= word >> 4;
	word |= word >> 2;
	word |= word >> 1;
	/* Remove one bit to make this a logarithm */
	word >>= 1;
	/* Count the bits set in the word */
	word -= (word >> 1) & 0x555;
	word = (word & 0x333) + ((word >> 2) & 0x333);
	word += (word >> 4);
	word += (word >> 8);
	return word & 15;
}
#endif

#if 0
static int debug = 0;
module_param(debug, bool, 0644);
#define DEBUG_ENT(fmt, arg...) do { if (debug) \
	printk(KERN_DEBUG "random %04d %04d %04d: " \
	fmt,\
	random_state->entropy_count,\
	sec_random_state->entropy_count,\
	urandom_state->entropy_count,\
	## arg); } while (0)
#else
#define DEBUG_ENT(fmt, arg...) do {} while (0)
#endif

/**********************************************************************
 *
 * OS independent entropy store.   Here are the functions which handle
 * storing entropy in an entropy pool.
 *
 **********************************************************************/

struct entropy_store {
	/* mostly-read data: */
	struct poolinfo poolinfo;
	__u32 *pool;
	const char *name;

	/* read-write data: */
	spinlock_t lock ____cacheline_aligned_in_smp;
	unsigned add_ptr;
	int entropy_count;
	int input_rotate;
};

/*
 * Initialize the entropy store.  The input argument is the size of
 * the random pool.
 *
 * Returns an negative error if there is a problem.
 */
static int create_entropy_store(int size, const char *name,
				struct entropy_store **ret_bucket)
{
	struct entropy_store *r;
	struct poolinfo *p;
	int poolwords;

	poolwords = (size + 3) / 4; /* Convert bytes->words */
	/* The pool size must be a multiple of 16 32-bit words */
	poolwords = ((poolwords + 15) / 16) * 16;

	for (p = poolinfo_table; p->poolwords; p++) {
		if (poolwords == p->poolwords)
			break;
	}
	if (p->poolwords == 0)
		return -EINVAL;

	r = kmalloc(sizeof(struct entropy_store), GFP_KERNEL);
	if (!r)
		return -ENOMEM;

	memset (r, 0, sizeof(struct entropy_store));
	r->poolinfo = *p;

	r->pool = kmalloc(POOLBYTES, GFP_KERNEL);
	if (!r->pool) {
		kfree(r);
		return -ENOMEM;
	}
	memset(r->pool, 0, POOLBYTES);
	spin_lock_init(&r->lock);
	r->name = name;
	*ret_bucket = r;
	return 0;
}

/* Clear the entropy pool and associated counters. */
static void clear_entropy_store(struct entropy_store *r)
{
	r->add_ptr = 0;
	r->entropy_count = 0;
	r->input_rotate = 0;
	memset(r->pool, 0, r->poolinfo.POOLBYTES);
}

/*
 * This function adds a byte into the entropy "pool".  It does not
 * update the entropy estimate.  The caller should call
 * credit_entropy_store if this is appropriate.
 *
 * The pool is stirred with a primitive polynomial of the appropriate
 * degree, and then twisted.  We twist by three bits at a time because
 * it's cheap to do so and helps slightly in the expected case where
 * the entropy is concentrated in the low-order bits.
 */
static void __add_entropy_words(struct entropy_store *r, const __u32 *in,
				int nwords, __u32 out[16])
{
	static __u32 const twist_table[8] = {
		0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158,
		0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 };
	unsigned long i, add_ptr, tap1, tap2, tap3, tap4, tap5;
	int new_rotate, input_rotate;
	int wordmask = r->poolinfo.poolwords - 1;
	__u32 w, next_w;
	unsigned long flags;

	/* Taps are constant, so we can load them without holding r->lock.  */
	tap1 = r->poolinfo.tap1;
	tap2 = r->poolinfo.tap2;
	tap3 = r->poolinfo.tap3;
	tap4 = r->poolinfo.tap4;
	tap5 = r->poolinfo.tap5;
	next_w = *in++;

	spin_lock_irqsave(&r->lock, flags);
	prefetch_range(r->pool, wordmask);
	input_rotate = r->input_rotate;
	add_ptr = r->add_ptr;

	while (nwords--) {
		w = rotate_left(input_rotate, next_w);
		if (nwords > 0)
			next_w = *in++;
		i = add_ptr = (add_ptr - 1) & wordmask;
		/*
		 * Normally, we add 7 bits of rotation to the pool.
		 * At the beginning of the pool, add an extra 7 bits
		 * rotation, so that successive passes spread the
		 * input bits across the pool evenly.
		 */
		new_rotate = input_rotate + 14;
		if (i)
			new_rotate = input_rotate + 7;
		input_rotate = new_rotate & 31;

		/* XOR in the various taps */
		w ^= r->pool[(i + tap1) & wordmask];
		w ^= r->pool[(i + tap2) & wordmask];
		w ^= r->pool[(i + tap3) & wordmask];
		w ^= r->pool[(i + tap4) & wordmask];
		w ^= r->pool[(i + tap5) & wordmask];
		w ^= r->pool[i];
		r->pool[i] = (w >> 3) ^ twist_table[w & 7];
	}

	r->input_rotate = input_rotate;
	r->add_ptr = add_ptr;

	if (out) {
		for (i = 0; i < 16; i++) {
			out[i] = r->pool[add_ptr];
			add_ptr = (add_ptr - 1) & wordmask;
		}
	}

	spin_unlock_irqrestore(&r->lock, flags);
}

static inline void add_entropy_words(struct entropy_store *r, const __u32 *in,
				     int nwords)
{
	__add_entropy_words(r, in, nwords, NULL);
}

/*
 * Credit (or debit) the entropy store with n bits of entropy
 */
static void credit_entropy_store(struct entropy_store *r, int nbits)
{
	unsigned long flags;

	spin_lock_irqsave(&r->lock, flags);

	if (r->entropy_count + nbits < 0) {
		DEBUG_ENT("negative entropy/overflow (%d+%d)\n",
			  r->entropy_count, nbits);
		r->entropy_count = 0;
	} else if (r->entropy_count + nbits > r->poolinfo.POOLBITS) {
		r->entropy_count = r->poolinfo.POOLBITS;
	} else {
		r->entropy_count += nbits;
		if (nbits)
			DEBUG_ENT("added %d entropy credits to %s\n",
				  nbits, r->name);
	}

	spin_unlock_irqrestore(&r->lock, flags);
}

/**********************************************************************
 *
 * Entropy batch input management
 *
 * We batch entropy to be added to avoid increasing interrupt latency
 *
 **********************************************************************/

struct sample {
	__u32 data[2];
	int credit;
};

static struct sample *batch_entropy_pool, *batch_entropy_copy;
static int batch_head, batch_tail;
static DEFINE_SPINLOCK(batch_lock);

static int batch_max;
static void batch_entropy_process(void *private_);
static DECLARE_WORK(batch_work, batch_entropy_process, NULL);

/* note: the size must be a power of 2 */
static int __init batch_entropy_init(int size, struct entropy_store *r)
{
	batch_entropy_pool = kmalloc(size*sizeof(struct sample), GFP_KERNEL);
	if (!batch_entropy_pool)
		return -1;
	batch_entropy_copy = kmalloc(size*sizeof(struct sample), GFP_KERNEL);
	if (!batch_entropy_copy) {
		kfree(batch_entropy_pool);
		return -1;
	}
	batch_head = batch_tail = 0;
	batch_work.data = r;
	batch_max = size;
	return 0;
}

/*
 * Changes to the entropy data is put into a queue rather than being added to
 * the entropy counts directly.  This is presumably to avoid doing heavy
 * hashing calculations during an interrupt in add_timer_randomness().
 * Instead, the entropy is only added to the pool by keventd.
 */
static void batch_entropy_store(u32 a, u32 b, int num)
{
	int new;
	unsigned long flags;

	if (!batch_max)
		return;

	spin_lock_irqsave(&batch_lock, flags);

	batch_entropy_pool[batch_head].data[0] = a;
	batch_entropy_pool[batch_head].data[1] = b;
	batch_entropy_pool[batch_head].credit = num;

	if (((batch_head - batch_tail) & (batch_max - 1)) >= (batch_max / 2))
		schedule_delayed_work(&batch_work, 1);

	new = (batch_head + 1) & (batch_max - 1);
	if (new == batch_tail)
		DEBUG_ENT("batch entropy buffer full\n");
	else
		batch_head = new;

	spin_unlock_irqrestore(&batch_lock, flags);
}

/*
 * Flush out the accumulated entropy operations, adding entropy to the passed
 * store (normally random_state).  If that store has enough entropy, alternate
 * between randomizing the data of the primary and secondary stores.
 */
static void batch_entropy_process(void *private_)
{
	struct entropy_store *r	= (struct entropy_store *) private_, *p;
	int max_entropy = r->poolinfo.POOLBITS;
	unsigned head, tail;

	/* Mixing into the pool is expensive, so copy over the batch
	 * data and release the batch lock. The pool is at least half
	 * full, so don't worry too much about copying only the used
	 * part.
	 */
	spin_lock_irq(&batch_lock);

	memcpy(batch_entropy_copy, batch_entropy_pool,
	       batch_max * sizeof(struct sample));

	head = batch_head;
	tail = batch_tail;
	batch_tail = batch_head;

	spin_unlock_irq(&batch_lock);

	p = r;
	while (head != tail) {
		if (r->entropy_count >= max_entropy) {
			r = (r == sec_random_state) ? random_state :
				sec_random_state;
			max_entropy = r->poolinfo.POOLBITS;
		}
		add_entropy_words(r, batch_entropy_copy[tail].data, 2);
		credit_entropy_store(r, batch_entropy_copy[tail].credit);
		tail = (tail + 1) & (batch_max - 1);
	}
	if (p->entropy_count >= random_read_wakeup_thresh)
		wake_up_interruptible(&random_read_wait);
}

/*********************************************************************
 *
 * Entropy input management
 *
 *********************************************************************/

/* There is one of these per entropy source */
struct timer_rand_state {
	cycles_t last_time;
	long last_delta,last_delta2;
	unsigned dont_count_entropy:1;
};

static struct timer_rand_state input_timer_state;
static struct timer_rand_state extract_timer_state;
static struct timer_rand_state *irq_timer_state[NR_IRQS];

/*
 * This function adds entropy to the entropy "pool" by using timing
 * delays.  It uses the timer_rand_state structure to make an estimate
 * of how many bits of entropy this call has added to the pool.
 *
 * The number "num" is also added to the pool - it should somehow describe
 * the type of event which just happened.  This is currently 0-255 for
 * keyboard scan codes, and 256 upwards for interrupts.
 *
 */
static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
{
	cycles_t data;
	long delta, delta2, delta3, time;
	int entropy = 0;

	preempt_disable();
	/* if over the trickle threshold, use only 1 in 4096 samples */
	if (random_state->entropy_count > trickle_thresh &&
	    (__get_cpu_var(trickle_count)++ & 0xfff))
		goto out;

	/*
	 * Calculate number of bits of randomness we probably added.
	 * We take into account the first, second and third-order deltas
	 * in order to make our estimate.
	 */
	time = jiffies;

	if (!state->dont_count_entropy) {
		delta = time - state->last_time;
		state->last_time = time;

		delta2 = delta - state->last_delta;
		state->last_delta = delta;

		delta3 = delta2 - state->last_delta2;
		state->last_delta2 = delta2;

		if (delta < 0)
			delta = -delta;
		if (delta2 < 0)
			delta2 = -delta2;
		if (delta3 < 0)
			delta3 = -delta3;
		if (delta > delta2)
			delta = delta2;
		if (delta > delta3)
			delta = delta3;

		/*
		 * delta is now minimum absolute delta.
		 * Round down by 1 bit on general principles,
		 * and limit entropy entimate to 12 bits.
		 */
		delta >>= 1;
		delta &= (1 << 12) - 1;

		entropy = int_ln_12bits(delta);
	}

	/*
	 * Use get_cycles() if implemented, otherwise fall back to
	 * jiffies.
	 */
	data = get_cycles();
	if (data)
		num ^= (u32)((data >> 31) >> 1);
	else
		data = time;

	batch_entropy_store(num, data, entropy);
out:
	preempt_enable();
}

extern void add_input_randomness(unsigned int type, unsigned int code,
				 unsigned int value)
{
	static unsigned char last_value;

	/* ignore autorepeat and the like */
	if (value == last_value)
		return;

	DEBUG_ENT("input event\n");
	last_value = value;
	add_timer_randomness(&input_timer_state,
			     (type << 4) ^ code ^ (code >> 4) ^ value);
}

void add_interrupt_randomness(int irq)
{
	if (irq >= NR_IRQS || irq_timer_state[irq] == 0)
		return;

	DEBUG_ENT("irq event %d\n", irq);
	add_timer_randomness(irq_timer_state[irq], 0x100 + irq);
}

void add_disk_randomness(struct gendisk *disk)
{
	if (!disk || !disk->random)
		return;
	/* first major is 1, so we get >= 0x200 here */
	DEBUG_ENT("disk event %d:%d\n", disk->major, disk->first_minor);

	add_timer_randomness(disk->random,
			     0x100 + MKDEV(disk->major, disk->first_minor));
}

EXPORT_SYMBOL(add_disk_randomness);

/******************************************************************
 *
 * Hash function definition
 *
 *******************************************************************/

/*
 * This chunk of code defines a function
 * void HASH_TRANSFORM(__u32 digest[HASH_BUFFER_SIZE + HASH_EXTRA_SIZE],
 * 		__u32 const data[16])
 *
 * The function hashes the input data to produce a digest in the first
 * HASH_BUFFER_SIZE words of the digest[] array, and uses HASH_EXTRA_SIZE
 * more words for internal purposes.  (This buffer is exported so the
 * caller can wipe it once rather than this code doing it each call,
 * and tacking it onto the end of the digest[] array is the quick and
 * dirty way of doing it.)
 *
 * It so happens that MD5 and SHA share most of the initial vector
 * used to initialize the digest[] array before the first call:
 * 1) 0x67452301
 * 2) 0xefcdab89
 * 3) 0x98badcfe
 * 4) 0x10325476
 * 5) 0xc3d2e1f0 (SHA only)
 *
 * For /dev/random purposes, the length of the data being hashed is
 * fixed in length, so appending a bit count in the usual way is not
 * cryptographically necessary.
 */

#ifdef USE_SHA

#define HASH_BUFFER_SIZE 5
#define HASH_EXTRA_SIZE 80
#define HASH_TRANSFORM SHATransform

/* Various size/speed tradeoffs are available.  Choose 0..3. */
#define SHA_CODE_SIZE 0

/*
 * SHA transform algorithm, taken from code written by Peter Gutmann,
 * and placed in the public domain.
 */

/* The SHA f()-functions.  */

#define f1(x,y,z)   (z ^ (x & (y ^ z)))		/* Rounds  0-19: x ? y : z */
#define f2(x,y,z)   (x ^ y ^ z)			/* Rounds 20-39: XOR */
#define f3(x,y,z)   ((x & y) + (z & (x ^ y)))	/* Rounds 40-59: majority */
#define f4(x,y,z)   (x ^ y ^ z)			/* Rounds 60-79: XOR */

/* The SHA Mysterious Constants */

#define K1  0x5A827999L			/* Rounds  0-19: sqrt(2) * 2^30 */
#define K2  0x6ED9EBA1L			/* Rounds 20-39: sqrt(3) * 2^30 */
#define K3  0x8F1BBCDCL			/* Rounds 40-59: sqrt(5) * 2^30 */
#define K4  0xCA62C1D6L			/* Rounds 60-79: sqrt(10) * 2^30 */

#define ROTL(n,X)  (((X) << n ) | ((X) >> (32 - n)))

#define subRound(a, b, c, d, e, f, k, data) \
    (e += ROTL(5, a) + f(b, c, d) + k + data, b = ROTL(30, b))

static void SHATransform(__u32 digest[85], __u32 const data[16])
{
	__u32 A, B, C, D, E;     /* Local vars */
	__u32 TEMP;
	int i;
#define W (digest + HASH_BUFFER_SIZE)	/* Expanded data array */

	/*
	 * Do the preliminary expansion of 16 to 80 words.  Doing it
	 * out-of-line line this is faster than doing it in-line on
	 * register-starved machines like the x86, and not really any
	 * slower on real processors.
	 */
	memcpy(W, data, 16*sizeof(__u32));
	for (i = 0; i < 64; i++) {
		TEMP = W[i] ^ W[i+2] ^ W[i+8] ^ W[i+13];
		W[i+16] = ROTL(1, TEMP);
	}

	/* Set up first buffer and local data buffer */
	A = digest[ 0 ];
	B = digest[ 1 ];
	C = digest[ 2 ];
	D = digest[ 3 ];
	E = digest[ 4 ];

	/* Heavy mangling, in 4 sub-rounds of 20 iterations each. */
#if SHA_CODE_SIZE == 0
	/*
	 * Approximately 50% of the speed of the largest version, but
	 * takes up 1/16 the space.  Saves about 6k on an i386 kernel.
	 */
	for (i = 0; i < 80; i++) {
		if (i < 40) {
			if (i < 20)
				TEMP = f1(B, C, D) + K1;
			else
				TEMP = f2(B, C, D) + K2;
		} else {
			if (i < 60)
				TEMP = f3(B, C, D) + K3;
			else
				TEMP = f4(B, C, D) + K4;
		}
		TEMP += ROTL(5, A) + E + W[i];
		E = D; D = C; C = ROTL(30, B); B = A; A = TEMP;
	}
#elif SHA_CODE_SIZE == 1
	for (i = 0; i < 20; i++) {
		TEMP = f1(B, C, D) + K1 + ROTL(5, A) + E + W[i];
		E = D; D = C; C = ROTL(30, B); B = A; A = TEMP;
	}
	for (; i < 40; i++) {
		TEMP = f2(B, C, D) + K2 + ROTL(5, A) + E + W[i];
		E = D; D = C; C = ROTL(30, B); B = A; A = TEMP;
	}
	for (; i < 60; i++) {
		TEMP = f3(B, C, D) + K3 + ROTL(5, A) + E + W[i];
		E = D; D = C; C = ROTL(30, B); B = A; A = TEMP;
	}
	for (; i < 80; i++) {
		TEMP = f4(B, C, D) + K4 + ROTL(5, A) + E + W[i];
		E = D; D = C; C = ROTL(30, B); B = A; A = TEMP;
	}
#elif SHA_CODE_SIZE == 2
	for (i = 0; i < 20; i += 5) {
		subRound(A, B, C, D, E, f1, K1, W[i  ]);
		subRound(E, A, B, C, D, f1, K1, W[i+1]);
		subRound(D, E, A, B, C, f1, K1, W[i+2]);
		subRound(C, D, E, A, B, f1, K1, W[i+3]);
		subRound(B, C, D, E, A, f1, K1, W[i+4]);
	}
	for (; i < 40; i += 5) {
		subRound(A, B, C, D, E, f2, K2, W[i  ]);
		subRound(E, A, B, C, D, f2, K2, W[i+1]);
		subRound(D, E, A, B, C, f2, K2, W[i+2]);
		subRound(C, D, E, A, B, f2, K2, W[i+3]);
		subRound(B, C, D, E, A, f2, K2, W[i+4]);
	}
	for (; i < 60; i += 5) {
		subRound(A, B, C, D, E, f3, K3, W[i  ]);
		subRound(E, A, B, C, D, f3, K3, W[i+1]);
		subRound(D, E, A, B, C, f3, K3, W[i+2]);
		subRound(C, D, E, A, B, f3, K3, W[i+3]);
		subRound(B, C, D, E, A, f3, K3, W[i+4]);
	}
	for (; i < 80; i += 5) {
		subRound(A, B, C, D, E, f4, K4, W[i  ]);
		subRound(E, A, B, C, D, f4, K4, W[i+1]);
		subRound(D, E, A, B, C, f4, K4, W[i+2]);
		subRound(C, D, E, A, B, f4, K4, W[i+3]);
		subRound(B, C, D, E, A, f4, K4, W[i+4]);
	}
#elif SHA_CODE_SIZE == 3 /* Really large version */
	subRound(A, B, C, D, E, f1, K1, W[ 0]);
	subRound(E, A, B, C, D, f1, K1, W[ 1]);
	subRound(D, E, A, B, C, f1, K1, W[ 2]);
	subRound(C, D, E, A, B, f1, K1, W[ 3]);
	subRound(B, C, D, E, A, f1, K1, W[ 4]);
	subRound(A, B, C, D, E, f1, K1, W[ 5]);
	subRound(E, A, B, C, D, f1, K1, W[ 6]);
	subRound(D, E, A, B, C, f1, K1, W[ 7]);
	subRound(C, D, E, A, B, f1, K1, W[ 8]);
	subRound(B, C, D, E, A, f1, K1, W[ 9]);
	subRound(A, B, C, D, E, f1, K1, W[10]);
	subRound(E, A, B, C, D, f1, K1, W[11]);
	subRound(D, E, A, B, C, f1, K1, W[12]);
	subRound(C, D, E, A, B, f1, K1, W[13]);
	subRound(B, C, D, E, A, f1, K1, W[14]);
	subRound(A, B, C, D, E, f1, K1, W[15]);
	subRound(E, A, B, C, D, f1, K1, W[16]);
	subRound(D, E, A, B, C, f1, K1, W[17]);
	subRound(C, D, E, A, B, f1, K1, W[18]);
	subRound(B, C, D, E, A, f1, K1, W[19]);

	subRound(A, B, C, D, E, f2, K2, W[20]);
	subRound(E, A, B, C, D, f2, K2, W[21]);
	subRound(D, E, A, B, C, f2, K2, W[22]);
	subRound(C, D, E, A, B, f2, K2, W[23]);
	subRound(B, C, D, E, A, f2, K2, W[24]);
	subRound(A, B, C, D, E, f2, K2, W[25]);
	subRound(E, A, B, C, D, f2, K2, W[26]);
	subRound(D, E, A, B, C, f2, K2, W[27]);
	subRound(C, D, E, A, B, f2, K2, W[28]);
	subRound(B, C, D, E, A, f2, K2, W[29]);
	subRound(A, B, C, D, E, f2, K2, W[30]);
	subRound(E, A, B, C, D, f2, K2, W[31]);
	subRound(D, E, A, B, C, f2, K2, W[32]);
	subRound(C, D, E, A, B, f2, K2, W[33]);
	subRound(B, C, D, E, A, f2, K2, W[34]);
	subRound(A, B, C, D, E, f2, K2, W[35]);
	subRound(E, A, B, C, D, f2, K2, W[36]);
	subRound(D, E, A, B, C, f2, K2, W[37]);
	subRound(C, D, E, A, B, f2, K2, W[38]);
	subRound(B, C, D, E, A, f2, K2, W[39]);

	subRound(A, B, C, D, E, f3, K3, W[40]);
	subRound(E, A, B, C, D, f3, K3, W[41]);
	subRound(D, E, A, B, C, f3, K3, W[42]);
	subRound(C, D, E, A, B, f3, K3, W[43]);
	subRound(B, C, D, E, A, f3, K3, W[44]);
	subRound(A, B, C, D, E, f3, K3, W[45]);
	subRound(E, A, B, C, D, f3, K3, W[46]);
	subRound(D, E, A, B, C, f3, K3, W[47]);
	subRound(C, D, E, A, B, f3, K3, W[48]);
	subRound(B, C, D, E, A, f3, K3, W[49]);
	subRound(A, B, C, D, E, f3, K3, W[50]);
	subRound(E, A, B, C, D, f3, K3, W[51]);
	subRound(D, E, A, B, C, f3, K3, W[52]);
	subRound(C, D, E, A, B, f3, K3, W[53]);
	subRound(B, C, D, E, A, f3, K3, W[54]);
	subRound(A, B, C, D, E, f3, K3, W[55]);
	subRound(E, A, B, C, D, f3, K3, W[56]);
	subRound(D, E, A, B, C, f3, K3, W[57]);
	subRound(C, D, E, A, B, f3, K3, W[58]);
	subRound(B, C, D, E, A, f3, K3, W[59]);

	subRound(A, B, C, D, E, f4, K4, W[60]);
	subRound(E, A, B, C, D, f4, K4, W[61]);
	subRound(D, E, A, B, C, f4, K4, W[62]);
	subRound(C, D, E, A, B, f4, K4, W[63]);
	subRound(B, C, D, E, A, f4, K4, W[64]);
	subRound(A, B, C, D, E, f4, K4, W[65]);
	subRound(E, A, B, C, D, f4, K4, W[66]);
	subRound(D, E, A, B, C, f4, K4, W[67]);
	subRound(C, D, E, A, B, f4, K4, W[68]);
	subRound(B, C, D, E, A, f4, K4, W[69]);
	subRound(A, B, C, D, E, f4, K4, W[70]);
	subRound(E, A, B, C, D, f4, K4, W[71]);
	subRound(D, E, A, B, C, f4, K4, W[72]);
	subRound(C, D, E, A, B, f4, K4, W[73]);
	subRound(B, C, D, E, A, f4, K4, W[74]);
	subRound(A, B, C, D, E, f4, K4, W[75]);
	subRound(E, A, B, C, D, f4, K4, W[76]);
	subRound(D, E, A, B, C, f4, K4, W[77]);
	subRound(C, D, E, A, B, f4, K4, W[78]);
	subRound(B, C, D, E, A, f4, K4, W[79]);
#else
#error Illegal SHA_CODE_SIZE
#endif

	/* Build message digest */
	digest[0] += A;
	digest[1] += B;
	digest[2] += C;
	digest[3] += D;
	digest[4] += E;

	/* W is wiped by the caller */
#undef W
}

#undef ROTL
#undef f1
#undef f2
#undef f3
#undef f4
#undef K1
#undef K2
#undef K3
#undef K4
#undef subRound

#else /* !USE_SHA - Use MD5 */

#define HASH_BUFFER_SIZE 4
#define HASH_EXTRA_SIZE 0
#define HASH_TRANSFORM MD5Transform

/*
 * MD5 transform algorithm, taken from code written by Colin Plumb,
 * and put into the public domain
 */

/* The four core functions - F1 is optimized somewhat */

/* #define F1(x, y, z) (x & y | ~x & z) */
#define F1(x, y, z) (z ^ (x & (y ^ z)))
#define F2(x, y, z) F1(z, x, y)
#define F3(x, y, z) (x ^ y ^ z)
#define F4(x, y, z) (y ^ (x | ~z))

/* This is the central step in the MD5 algorithm. */
#define MD5STEP(f, w, x, y, z, data, s) \
	(w += f(x, y, z) + data,  w = w << s | w >> (32 - s),  w += x )

/*
 * The core of the MD5 algorithm, this alters an existing MD5 hash to
 * reflect the addition of 16 longwords of new data.  MD5Update blocks
 * the data and converts bytes into longwords for this routine.
 */
static void MD5Transform(__u32 buf[HASH_BUFFER_SIZE], __u32 const in[16])
{
	__u32 a, b, c, d;

	a = buf[0];
	b = buf[1];
	c = buf[2];
	d = buf[3];

	MD5STEP(F1, a, b, c, d, in[ 0]+0xd76aa478,  7);
	MD5STEP(F1, d, a, b, c, in[ 1]+0xe8c7b756, 12);
	MD5STEP(F1, c, d, a, b, in[ 2]+0x242070db, 17);
	MD5STEP(F1, b, c, d, a, in[ 3]+0xc1bdceee, 22);
	MD5STEP(F1, a, b, c, d, in[ 4]+0xf57c0faf,  7);
	MD5STEP(F1, d, a, b, c, in[ 5]+0x4787c62a, 12);
	MD5STEP(F1, c, d, a, b, in[ 6]+0xa8304613, 17);
	MD5STEP(F1, b, c, d, a, in[ 7]+0xfd469501, 22);
	MD5STEP(F1, a, b, c, d, in[ 8]+0x698098d8,  7);
	MD5STEP(F1, d, a, b, c, in[ 9]+0x8b44f7af, 12);
	MD5STEP(F1, c, d, a, b, in[10]+0xffff5bb1, 17);
	MD5STEP(F1, b, c, d, a, in[11]+0x895cd7be, 22);
	MD5STEP(F1, a, b, c, d, in[12]+0x6b901122,  7);
	MD5STEP(F1, d, a, b, c, in[13]+0xfd987193, 12);
	MD5STEP(F1, c, d, a, b, in[14]+0xa679438e, 17);
	MD5STEP(F1, b, c, d, a, in[15]+0x49b40821, 22);

	MD5STEP(F2, a, b, c, d, in[ 1]+0xf61e2562,  5);
	MD5STEP(F2, d, a, b, c, in[ 6]+0xc040b340,  9);
	MD5STEP(F2, c, d, a, b, in[11]+0x265e5a51, 14);
	MD5STEP(F2, b, c, d, a, in[ 0]+0xe9b6c7aa, 20);
	MD5STEP(F2, a, b, c, d, in[ 5]+0xd62f105d,  5);
	MD5STEP(F2, d, a, b, c, in[10]+0x02441453,  9);
	MD5STEP(F2, c, d, a, b, in[15]+0xd8a1e681, 14);
	MD5STEP(F2, b, c, d, a, in[ 4]+0xe7d3fbc8, 20);
	MD5STEP(F2, a, b, c, d, in[ 9]+0x21e1cde6,  5);
	MD5STEP(F2, d, a, b, c, in[14]+0xc33707d6,  9);
	MD5STEP(F2, c, d, a, b, in[ 3]+0xf4d50d87, 14);
	MD5STEP(F2, b, c, d, a, in[ 8]+0x455a14ed, 20);
	MD5STEP(F2, a, b, c, d, in[13]+0xa9e3e905,  5);
	MD5STEP(F2, d, a, b, c, in[ 2]+0xfcefa3f8,  9);
	MD5STEP(F2, c, d, a, b, in[ 7]+0x676f02d9, 14);
	MD5STEP(F2, b, c, d, a, in[12]+0x8d2a4c8a, 20);

	MD5STEP(F3, a, b, c, d, in[ 5]+0xfffa3942,  4);
	MD5STEP(F3, d, a, b, c, in[ 8]+0x8771f681, 11);
	MD5STEP(F3, c, d, a, b, in[11]+0x6d9d6122, 16);
	MD5STEP(F3, b, c, d, a, in[14]+0xfde5380c, 23);
	MD5STEP(F3, a, b, c, d, in[ 1]+0xa4beea44,  4);
	MD5STEP(F3, d, a, b, c, in[ 4]+0x4bdecfa9, 11);
	MD5STEP(F3, c, d, a, b, in[ 7]+0xf6bb4b60, 16);
	MD5STEP(F3, b, c, d, a, in[10]+0xbebfbc70, 23);
	MD5STEP(F3, a, b, c, d, in[13]+0x289b7ec6,  4);
	MD5STEP(F3, d, a, b, c, in[ 0]+0xeaa127fa, 11);
	MD5STEP(F3, c, d, a, b, in[ 3]+0xd4ef3085, 16);
	MD5STEP(F3, b, c, d, a, in[ 6]+0x04881d05, 23);
	MD5STEP(F3, a, b, c, d, in[ 9]+0xd9d4d039,  4);
	MD5STEP(F3, d, a, b, c, in[12]+0xe6db99e5, 11);
	MD5STEP(F3, c, d, a, b, in[15]+0x1fa27cf8, 16);
	MD5STEP(F3, b, c, d, a, in[ 2]+0xc4ac5665, 23);

	MD5STEP(F4, a, b, c, d, in[ 0]+0xf4292244,  6);
	MD5STEP(F4, d, a, b, c, in[ 7]+0x432aff97, 10);
	MD5STEP(F4, c, d, a, b, in[14]+0xab9423a7, 15);
	MD5STEP(F4, b, c, d, a, in[ 5]+0xfc93a039, 21);
	MD5STEP(F4, a, b, c, d, in[12]+0x655b59c3,  6);
	MD5STEP(F4, d, a, b, c, in[ 3]+0x8f0ccc92, 10);
	MD5STEP(F4, c, d, a, b, in[10]+0xffeff47d, 15);
	MD5STEP(F4, b, c, d, a, in[ 1]+0x85845dd1, 21);
	MD5STEP(F4, a, b, c, d, in[ 8]+0x6fa87e4f,  6);
	MD5STEP(F4, d, a, b, c, in[15]+0xfe2ce6e0, 10);
	MD5STEP(F4, c, d, a, b, in[ 6]+0xa3014314, 15);
	MD5STEP(F4, b, c, d, a, in[13]+0x4e0811a1, 21);
	MD5STEP(F4, a, b, c, d, in[ 4]+0xf7537e82,  6);
	MD5STEP(F4, d, a, b, c, in[11]+0xbd3af235, 10);
	MD5STEP(F4, c, d, a, b, in[ 2]+0x2ad7d2bb, 15);
	MD5STEP(F4, b, c, d, a, in[ 9]+0xeb86d391, 21);

	buf[0] += a;
	buf[1] += b;
	buf[2] += c;
	buf[3] += d;
}

#undef F1
#undef F2
#undef F3
#undef F4
#undef MD5STEP

#endif /* !USE_SHA */

/*********************************************************************
 *
 * Entropy extraction routines
 *
 *********************************************************************/

#define EXTRACT_ENTROPY_USER		1
#define EXTRACT_ENTROPY_SECONDARY	2
#define EXTRACT_ENTROPY_LIMIT		4
#define TMP_BUF_SIZE			(HASH_BUFFER_SIZE + HASH_EXTRA_SIZE)
#define SEC_XFER_SIZE			(TMP_BUF_SIZE*4)

static ssize_t extract_entropy(struct entropy_store *r, void * buf,
			       size_t nbytes, int flags);

/*
 * This utility inline function is responsible for transfering entropy
 * from the primary pool to the secondary extraction pool. We make
 * sure we pull enough for a 'catastrophic reseed'.
 */
static inline void xfer_secondary_pool(struct entropy_store *r,
				       size_t nbytes, __u32 *tmp)
{
	if (r->entropy_count < nbytes * 8 &&
	    r->entropy_count < r->poolinfo.POOLBITS) {
		int bytes = max_t(int, random_read_wakeup_thresh / 8,
				min_t(int, nbytes, TMP_BUF_SIZE));

		DEBUG_ENT("going to reseed %s with %d bits "
			  "(%d of %d requested)\n",
			  r->name, bytes * 8, nbytes * 8, r->entropy_count);

		bytes=extract_entropy(random_state, tmp, bytes,
				      EXTRACT_ENTROPY_LIMIT);
		add_entropy_words(r, tmp, (bytes + 3) / 4);
		credit_entropy_store(r, bytes*8);
	}
}

/*
 * This function extracts randomness from the "entropy pool", and
 * returns it in a buffer.  This function computes how many remaining
 * bits of entropy are left in the pool, but it does not restrict the
 * number of bytes that are actually obtained.  If the EXTRACT_ENTROPY_USER
 * flag is given, then the buf pointer is assumed to be in user space.
 *
 * If the EXTRACT_ENTROPY_SECONDARY flag is given, then we are actually
 * extracting entropy from the secondary pool, and can refill from the
 * primary pool if needed.
 *
 * Note: extract_entropy() assumes that .poolwords is a multiple of 16 words.
 */
static ssize_t extract_entropy(struct entropy_store *r, void * buf,
			       size_t nbytes, int flags)
{
	ssize_t ret, i;
	__u32 tmp[TMP_BUF_SIZE], data[16];
	__u32 x;
	unsigned long cpuflags;

	/* Redundant, but just in case... */
	if (r->entropy_count > r->poolinfo.POOLBITS)
		r->entropy_count = r->poolinfo.POOLBITS;

	if (flags & EXTRACT_ENTROPY_SECONDARY)
		xfer_secondary_pool(r, nbytes, tmp);

	/* Hold lock while accounting */
	spin_lock_irqsave(&r->lock, cpuflags);

	DEBUG_ENT("trying to extract %d bits from %s\n",
		  nbytes * 8, r->name);

	if (flags & EXTRACT_ENTROPY_LIMIT && nbytes >= r->entropy_count / 8)
		nbytes = r->entropy_count / 8;

	if (r->entropy_count / 8 >= nbytes)
		r->entropy_count -= nbytes*8;
	else
		r->entropy_count = 0;

	if (r->entropy_count < random_write_wakeup_thresh)
		wake_up_interruptible(&random_write_wait);

	DEBUG_ENT("debiting %d entropy credits from %s%s\n",
		  nbytes * 8, r->name,
		  flags & EXTRACT_ENTROPY_LIMIT ? "" : " (unlimited)");

	spin_unlock_irqrestore(&r->lock, cpuflags);

	ret = 0;
	while (nbytes) {
		/*
		 * Check if we need to break out or reschedule....
		 */
		if ((flags & EXTRACT_ENTROPY_USER) && need_resched()) {
			if (signal_pending(current)) {
				if (ret == 0)
					ret = -ERESTARTSYS;
				break;
			}

			schedule();
		}

		/* Hash the pool to get the output */
		tmp[0] = 0x67452301;
		tmp[1] = 0xefcdab89;
		tmp[2] = 0x98badcfe;
		tmp[3] = 0x10325476;
#ifdef USE_SHA
		tmp[4] = 0xc3d2e1f0;
#endif
		/*
		 * As we hash the pool, we mix intermediate values of
		 * the hash back into the pool.  This eliminates
		 * backtracking attacks (where the attacker knows
		 * the state of the pool plus the current outputs, and
		 * attempts to find previous ouputs), unless the hash
		 * function can be inverted.
		 */
		for (i = 0, x = 0; i < r->poolinfo.poolwords; i += 16, x+=2) {
			HASH_TRANSFORM(tmp, r->pool+i);
			add_entropy_words(r, &tmp[x%HASH_BUFFER_SIZE], 1);
		}

		/*
		 * To avoid duplicates, we atomically extract a
		 * portion of the pool while mixing, and hash one
		 * final time.
		 */
		__add_entropy_words(r, &tmp[x%HASH_BUFFER_SIZE], 1, data);
		HASH_TRANSFORM(tmp, data);

		/*
		 * In case the hash function has some recognizable
		 * output pattern, we fold it in half.
		 */
		for (i = 0; i <  HASH_BUFFER_SIZE/2; i++)
			tmp[i] ^= tmp[i + (HASH_BUFFER_SIZE+1)/2];
#if HASH_BUFFER_SIZE & 1	/* There's a middle word to deal with */
		x = tmp[HASH_BUFFER_SIZE/2];
		x ^= (x >> 16);		/* Fold it in half */
		((__u16 *)tmp)[HASH_BUFFER_SIZE-1] = (__u16)x;
#endif

		/* Copy data to destination buffer */
		i = min(nbytes, HASH_BUFFER_SIZE*sizeof(__u32)/2);
		if (flags & EXTRACT_ENTROPY_USER) {
			i -= copy_to_user(buf, (__u8 const *)tmp, i);
			if (!i) {
				ret = -EFAULT;
				break;
			}
		} else
			memcpy(buf, (__u8 const *)tmp, i);

		nbytes -= i;
		buf += i;
		ret += i;
	}

	/* Wipe data just returned from memory */
	memset(tmp, 0, sizeof(tmp));

	return ret;
}

/*
 * This function is the exported kernel interface.  It returns some
 * number of good random numbers, suitable for seeding TCP sequence
 * numbers, etc.
 */
void get_random_bytes(void *buf, int nbytes)
{
	struct entropy_store *r = urandom_state;
	int flags = EXTRACT_ENTROPY_SECONDARY;

	if (!r)
		r = sec_random_state;
	if (!r) {
		r = random_state;
		flags = 0;
	}
	if (!r) {
		printk(KERN_NOTICE "get_random_bytes called before "
				   "random driver initialization\n");
		return;
	}
	extract_entropy(r, (char *) buf, nbytes, flags);
}

EXPORT_SYMBOL(get_random_bytes);

/*********************************************************************
 *
 * Functions to interface with Linux
 *
 *********************************************************************/

/*
 * Initialize the random pool with standard stuff.
 *
 * NOTE: This is an OS-dependent function.
 */
static void init_std_data(struct entropy_store *r)
{
	struct timeval tv;
	__u32 words[2];
	char *p;
	int i;

	do_gettimeofday(&tv);
	words[0] = tv.tv_sec;
	words[1] = tv.tv_usec;
	add_entropy_words(r, words, 2);

	/*
	 *	This doesn't lock system.utsname. However, we are generating
	 *	entropy so a race with a name set here is fine.
	 */
	p = (char *) &system_utsname;
	for (i = sizeof(system_utsname) / sizeof(words); i; i--) {
		memcpy(words, p, sizeof(words));
		add_entropy_words(r, words, sizeof(words)/4);
		p += sizeof(words);
	}
}

static int __init rand_initialize(void)
{
	int i;

	if (create_entropy_store(DEFAULT_POOL_SIZE, "primary", &random_state))
		goto err;
	if (batch_entropy_init(BATCH_ENTROPY_SIZE, random_state))
		goto err;
	if (create_entropy_store(SECONDARY_POOL_SIZE, "secondary",
				 &sec_random_state))
		goto err;
	if (create_entropy_store(SECONDARY_POOL_SIZE, "urandom",
				 &urandom_state))
		goto err;
	clear_entropy_store(random_state);
	clear_entropy_store(sec_random_state);
	clear_entropy_store(urandom_state);
	init_std_data(random_state);
	init_std_data(sec_random_state);
	init_std_data(urandom_state);
#ifdef CONFIG_SYSCTL
	sysctl_init_random(random_state);
#endif
	for (i = 0; i < NR_IRQS; i++)
		irq_timer_state[i] = NULL;
	memset(&input_timer_state, 0, sizeof(struct timer_rand_state));
	memset(&extract_timer_state, 0, sizeof(struct timer_rand_state));
	extract_timer_state.dont_count_entropy = 1;
	return 0;
err:
	return -1;
}
module_init(rand_initialize);

void rand_initialize_irq(int irq)
{
	struct timer_rand_state *state;

	if (irq >= NR_IRQS || irq_timer_state[irq])
		return;

	/*
	 * If kmalloc returns null, we just won't use that entropy
	 * source.
	 */
	state = kmalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
	if (state) {
		memset(state, 0, sizeof(struct timer_rand_state));
		irq_timer_state[irq] = state;
	}
}

void rand_initialize_disk(struct gendisk *disk)
{
	struct timer_rand_state *state;

	/*
	 * If kmalloc returns null, we just won't use that entropy
	 * source.
	 */
	state = kmalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
	if (state) {
		memset(state, 0, sizeof(struct timer_rand_state));
		disk->random = state;
	}
}

static ssize_t
random_read(struct file * file, char __user * buf, size_t nbytes, loff_t *ppos)
{
	DECLARE_WAITQUEUE(wait, current);
	ssize_t n, retval = 0, count = 0;

	if (nbytes == 0)
		return 0;

	while (nbytes > 0) {
		n = nbytes;
		if (n > SEC_XFER_SIZE)
			n = SEC_XFER_SIZE;

		DEBUG_ENT("reading %d bits\n", n*8);

		n = extract_entropy(sec_random_state, buf, n,
				    EXTRACT_ENTROPY_USER |
				    EXTRACT_ENTROPY_LIMIT |
				    EXTRACT_ENTROPY_SECONDARY);

		DEBUG_ENT("read got %d bits (%d still needed)\n",
			  n*8, (nbytes-n)*8);

		if (n == 0) {
			if (file->f_flags & O_NONBLOCK) {
				retval = -EAGAIN;
				break;
			}
			if (signal_pending(current)) {
				retval = -ERESTARTSYS;
				break;
			}

			set_current_state(TASK_INTERRUPTIBLE);
			add_wait_queue(&random_read_wait, &wait);

			if (sec_random_state->entropy_count / 8 == 0)
				schedule();

			set_current_state(TASK_RUNNING);
			remove_wait_queue(&random_read_wait, &wait);

			continue;
		}

		if (n < 0) {
			retval = n;
			break;
		}
		count += n;
		buf += n;
		nbytes -= n;
		break;		/* This break makes the device work */
				/* like a named pipe */
	}

	/*
	 * If we gave the user some bytes, update the access time.
	 */
	if (count)
		file_accessed(file);

	return (count ? count : retval);
}

static ssize_t
urandom_read(struct file * file, char __user * buf,
		      size_t nbytes, loff_t *ppos)
{
	int flags = EXTRACT_ENTROPY_USER;
	unsigned long cpuflags;

	spin_lock_irqsave(&random_state->lock, cpuflags);
	if (random_state->entropy_count > random_state->poolinfo.POOLBITS)
		flags |= EXTRACT_ENTROPY_SECONDARY;
	spin_unlock_irqrestore(&random_state->lock, cpuflags);

	return extract_entropy(urandom_state, buf, nbytes, flags);
}

static unsigned int
random_poll(struct file *file, poll_table * wait)
{
	unsigned int mask;

	poll_wait(file, &random_read_wait, wait);
	poll_wait(file, &random_write_wait, wait);
	mask = 0;
	if (random_state->entropy_count >= random_read_wakeup_thresh)
		mask |= POLLIN | POLLRDNORM;
	if (random_state->entropy_count < random_write_wakeup_thresh)
		mask |= POLLOUT | POLLWRNORM;
	return mask;
}

static ssize_t
random_write(struct file * file, const char __user * buffer,
	     size_t count, loff_t *ppos)
{
	int ret = 0;
	size_t bytes;
	__u32 buf[16];
	const char __user *p = buffer;
	size_t c = count;

	while (c > 0) {
		bytes = min(c, sizeof(buf));

		bytes -= copy_from_user(&buf, p, bytes);
		if (!bytes) {
			ret = -EFAULT;
			break;
		}
		c -= bytes;
		p += bytes;

		add_entropy_words(random_state, buf, (bytes + 3) / 4);
	}
	if (p == buffer) {
		return (ssize_t)ret;
	} else {
		struct inode *inode = file->f_dentry->d_inode;
	        inode->i_mtime = current_fs_time(inode->i_sb);
		mark_inode_dirty(inode);
		return (ssize_t)(p - buffer);
	}
}

static int
random_ioctl(struct inode * inode, struct file * file,
	     unsigned int cmd, unsigned long arg)
{
	int size, ent_count;
	int __user *p = (int __user *)arg;
	int retval;

	switch (cmd) {
	case RNDGETENTCNT:
		ent_count = random_state->entropy_count;
		if (put_user(ent_count, p))
			return -EFAULT;
		return 0;
	case RNDADDTOENTCNT:
		if (!capable(CAP_SYS_ADMIN))
			return -EPERM;
		if (get_user(ent_count, p))
			return -EFAULT;
		credit_entropy_store(random_state, ent_count);
		/*
		 * Wake up waiting processes if we have enough
		 * entropy.
		 */
		if (random_state->entropy_count >= random_read_wakeup_thresh)
			wake_up_interruptible(&random_read_wait);
		return 0;
	case RNDADDENTROPY:
		if (!capable(CAP_SYS_ADMIN))
			return -EPERM;
		if (get_user(ent_count, p++))
			return -EFAULT;
		if (ent_count < 0)
			return -EINVAL;
		if (get_user(size, p++))
			return -EFAULT;
		retval = random_write(file, (const char __user *) p,
				      size, &file->f_pos);
		if (retval < 0)
			return retval;
		credit_entropy_store(random_state, ent_count);
		/*
		 * Wake up waiting processes if we have enough
		 * entropy.
		 */
		if (random_state->entropy_count >= random_read_wakeup_thresh)
			wake_up_interruptible(&random_read_wait);
		return 0;
	case RNDZAPENTCNT:
		if (!capable(CAP_SYS_ADMIN))
			return -EPERM;
		random_state->entropy_count = 0;
		return 0;
	case RNDCLEARPOOL:
		/* Clear the entropy pool and associated counters. */
		if (!capable(CAP_SYS_ADMIN))
			return -EPERM;
		clear_entropy_store(random_state);
		init_std_data(random_state);
		return 0;
	default:
		return -EINVAL;
	}
}

struct file_operations random_fops = {
	.read  = random_read,
	.write = random_write,
	.poll  = random_poll,
	.ioctl = random_ioctl,
};

struct file_operations urandom_fops = {
	.read  = urandom_read,
	.write = random_write,
	.ioctl = random_ioctl,
};

/***************************************************************
 * Random UUID interface
 *
 * Used here for a Boot ID, but can be useful for other kernel
 * drivers.
 ***************************************************************/

/*
 * Generate random UUID
 */
void generate_random_uuid(unsigned char uuid_out[16])
{
	get_random_bytes(uuid_out, 16);
	/* Set UUID version to 4 --- truely random generation */
	uuid_out[6] = (uuid_out[6] & 0x0F) | 0x40;
	/* Set the UUID variant to DCE */
	uuid_out[8] = (uuid_out[8] & 0x3F) | 0x80;
}

EXPORT_SYMBOL(generate_random_uuid);

/********************************************************************
 *
 * Sysctl interface
 *
 ********************************************************************/

#ifdef CONFIG_SYSCTL

#include <linux/sysctl.h>

static int min_read_thresh, max_read_thresh;
static int min_write_thresh, max_write_thresh;
static char sysctl_bootid[16];

/*
 * These functions is used to return both the bootid UUID, and random
 * UUID.  The difference is in whether table->data is NULL; if it is,
 * then a new UUID is generated and returned to the user.
 *
 * If the user accesses this via the proc interface, it will be returned
 * as an ASCII string in the standard UUID format.  If accesses via the
 * sysctl system call, it is returned as 16 bytes of binary data.
 */
static int proc_do_uuid(ctl_table *table, int write, struct file *filp,
			void __user *buffer, size_t *lenp, loff_t *ppos)
{
	ctl_table fake_table;
	unsigned char buf[64], tmp_uuid[16], *uuid;

	uuid = table->data;
	if (!uuid) {
		uuid = tmp_uuid;
		uuid[8] = 0;
	}
	if (uuid[8] == 0)
		generate_random_uuid(uuid);

	sprintf(buf, "%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-"
		"%02x%02x%02x%02x%02x%02x",
		uuid[0],  uuid[1],  uuid[2],  uuid[3],
		uuid[4],  uuid[5],  uuid[6],  uuid[7],
		uuid[8],  uuid[9],  uuid[10], uuid[11],
		uuid[12], uuid[13], uuid[14], uuid[15]);
	fake_table.data = buf;
	fake_table.maxlen = sizeof(buf);

	return proc_dostring(&fake_table, write, filp, buffer, lenp, ppos);
}

static int uuid_strategy(ctl_table *table, int __user *name, int nlen,
			 void __user *oldval, size_t __user *oldlenp,
			 void __user *newval, size_t newlen, void **context)
{
	unsigned char tmp_uuid[16], *uuid;
	unsigned int len;

	if (!oldval || !oldlenp)
		return 1;

	uuid = table->data;
	if (!uuid) {
		uuid = tmp_uuid;
		uuid[8] = 0;
	}
	if (uuid[8] == 0)
		generate_random_uuid(uuid);

	if (get_user(len, oldlenp))
		return -EFAULT;
	if (len) {
		if (len > 16)
			len = 16;
		if (copy_to_user(oldval, uuid, len) ||
		    put_user(len, oldlenp))
			return -EFAULT;
	}
	return 1;
}

static int sysctl_poolsize = DEFAULT_POOL_SIZE;
ctl_table random_table[] = {
	{
		.ctl_name 	= RANDOM_POOLSIZE,
		.procname	= "poolsize",
		.data		= &sysctl_poolsize,
		.maxlen		= sizeof(int),
		.mode		= 0444,
		.proc_handler	= &proc_dointvec,
	},
	{
		.ctl_name	= RANDOM_ENTROPY_COUNT,
		.procname	= "entropy_avail",
		.maxlen		= sizeof(int),
		.mode		= 0444,
		.proc_handler	= &proc_dointvec,
	},
	{
		.ctl_name	= RANDOM_READ_THRESH,
		.procname	= "read_wakeup_threshold",
		.data		= &random_read_wakeup_thresh,
		.maxlen		= sizeof(int),
		.mode		= 0644,
		.proc_handler	= &proc_dointvec_minmax,
		.strategy	= &sysctl_intvec,
		.extra1		= &min_read_thresh,
		.extra2		= &max_read_thresh,
	},
	{
		.ctl_name	= RANDOM_WRITE_THRESH,
		.procname	= "write_wakeup_threshold",
		.data		= &random_write_wakeup_thresh,
		.maxlen		= sizeof(int),
		.mode		= 0644,
		.proc_handler	= &proc_dointvec_minmax,
		.strategy	= &sysctl_intvec,
		.extra1		= &min_write_thresh,
		.extra2		= &max_write_thresh,
	},
	{
		.ctl_name	= RANDOM_BOOT_ID,
		.procname	= "boot_id",
		.data		= &sysctl_bootid,
		.maxlen		= 16,
		.mode		= 0444,
		.proc_handler	= &proc_do_uuid,
		.strategy	= &uuid_strategy,
	},
	{
		.ctl_name	= RANDOM_UUID,
		.procname	= "uuid",
		.maxlen		= 16,
		.mode		= 0444,
		.proc_handler	= &proc_do_uuid,
		.strategy	= &uuid_strategy,
	},
	{ .ctl_name = 0 }
};

static void sysctl_init_random(struct entropy_store *random_state)
{
	min_read_thresh = 8;
	min_write_thresh = 0;
	max_read_thresh = max_write_thresh = random_state->poolinfo.POOLBITS;
	random_table[1].data = &random_state->entropy_count;
}
#endif 	/* CONFIG_SYSCTL */

/********************************************************************
 *
 * Random funtions for networking
 *
 ********************************************************************/

#ifdef CONFIG_INET
/*
 * TCP initial sequence number picking.  This uses the random number
 * generator to pick an initial secret value.  This value is hashed
 * along with the TCP endpoint information to provide a unique
 * starting point for each pair of TCP endpoints.  This defeats
 * attacks which rely on guessing the initial TCP sequence number.
 * This algorithm was suggested by Steve Bellovin.
 *
 * Using a very strong hash was taking an appreciable amount of the total
 * TCP connection establishment time, so this is a weaker hash,
 * compensated for by changing the secret periodically.
 */

/* F, G and H are basic MD4 functions: selection, majority, parity */
#define F(x, y, z) ((z) ^ ((x) & ((y) ^ (z))))
#define G(x, y, z) (((x) & (y)) + (((x) ^ (y)) & (z)))
#define H(x, y, z) ((x) ^ (y) ^ (z))

/*
 * The generic round function.  The application is so specific that
 * we don't bother protecting all the arguments with parens, as is generally
 * good macro practice, in favor of extra legibility.
 * Rotation is separate from addition to prevent recomputation
 */
#define ROUND(f, a, b, c, d, x, s)	\
	(a += f(b, c, d) + x, a = (a << s) | (a >> (32 - s)))
#define K1 0
#define K2 013240474631UL
#define K3 015666365641UL

/*
 * Basic cut-down MD4 transform.  Returns only 32 bits of result.
 */
static __u32 halfMD4Transform (__u32 const buf[4], __u32 const in[8])
{
	__u32 a = buf[0], b = buf[1], c = buf[2], d = buf[3];

	/* Round 1 */
	ROUND(F, a, b, c, d, in[0] + K1,  3);
	ROUND(F, d, a, b, c, in[1] + K1,  7);
	ROUND(F, c, d, a, b, in[2] + K1, 11);
	ROUND(F, b, c, d, a, in[3] + K1, 19);
	ROUND(F, a, b, c, d, in[4] + K1,  3);
	ROUND(F, d, a, b, c, in[5] + K1,  7);
	ROUND(F, c, d, a, b, in[6] + K1, 11);
	ROUND(F, b, c, d, a, in[7] + K1, 19);

	/* Round 2 */
	ROUND(G, a, b, c, d, in[1] + K2,  3);
	ROUND(G, d, a, b, c, in[3] + K2,  5);
	ROUND(G, c, d, a, b, in[5] + K2,  9);
	ROUND(G, b, c, d, a, in[7] + K2, 13);
	ROUND(G, a, b, c, d, in[0] + K2,  3);
	ROUND(G, d, a, b, c, in[2] + K2,  5);
	ROUND(G, c, d, a, b, in[4] + K2,  9);
	ROUND(G, b, c, d, a, in[6] + K2, 13);

	/* Round 3 */
	ROUND(H, a, b, c, d, in[3] + K3,  3);
	ROUND(H, d, a, b, c, in[7] + K3,  9);
	ROUND(H, c, d, a, b, in[2] + K3, 11);
	ROUND(H, b, c, d, a, in[6] + K3, 15);
	ROUND(H, a, b, c, d, in[1] + K3,  3);
	ROUND(H, d, a, b, c, in[5] + K3,  9);
	ROUND(H, c, d, a, b, in[0] + K3, 11);
	ROUND(H, b, c, d, a, in[4] + K3, 15);

	return buf[1] + b;	/* "most hashed" word */
	/* Alternative: return sum of all words? */
}

#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)

static __u32 twothirdsMD4Transform (__u32 const buf[4], __u32 const in[12])
{
	__u32 a = buf[0], b = buf[1], c = buf[2], d = buf[3];

	/* Round 1 */
	ROUND(F, a, b, c, d, in[ 0] + K1,  3);
	ROUND(F, d, a, b, c, in[ 1] + K1,  7);
	ROUND(F, c, d, a, b, in[ 2] + K1, 11);
	ROUND(F, b, c, d, a, in[ 3] + K1, 19);
	ROUND(F, a, b, c, d, in[ 4] + K1,  3);
	ROUND(F, d, a, b, c, in[ 5] + K1,  7);
	ROUND(F, c, d, a, b, in[ 6] + K1, 11);
	ROUND(F, b, c, d, a, in[ 7] + K1, 19);
	ROUND(F, a, b, c, d, in[ 8] + K1,  3);
	ROUND(F, d, a, b, c, in[ 9] + K1,  7);
	ROUND(F, c, d, a, b, in[10] + K1, 11);
	ROUND(F, b, c, d, a, in[11] + K1, 19);

	/* Round 2 */
	ROUND(G, a, b, c, d, in[ 1] + K2,  3);
	ROUND(G, d, a, b, c, in[ 3] + K2,  5);
	ROUND(G, c, d, a, b, in[ 5] + K2,  9);
	ROUND(G, b, c, d, a, in[ 7] + K2, 13);
	ROUND(G, a, b, c, d, in[ 9] + K2,  3);
	ROUND(G, d, a, b, c, in[11] + K2,  5);
	ROUND(G, c, d, a, b, in[ 0] + K2,  9);
	ROUND(G, b, c, d, a, in[ 2] + K2, 13);
	ROUND(G, a, b, c, d, in[ 4] + K2,  3);
	ROUND(G, d, a, b, c, in[ 6] + K2,  5);
	ROUND(G, c, d, a, b, in[ 8] + K2,  9);
	ROUND(G, b, c, d, a, in[10] + K2, 13);

	/* Round 3 */
	ROUND(H, a, b, c, d, in[ 3] + K3,  3);
	ROUND(H, d, a, b, c, in[ 7] + K3,  9);
	ROUND(H, c, d, a, b, in[11] + K3, 11);
	ROUND(H, b, c, d, a, in[ 2] + K3, 15);
	ROUND(H, a, b, c, d, in[ 6] + K3,  3);
	ROUND(H, d, a, b, c, in[10] + K3,  9);
	ROUND(H, c, d, a, b, in[ 1] + K3, 11);
	ROUND(H, b, c, d, a, in[ 5] + K3, 15);
	ROUND(H, a, b, c, d, in[ 9] + K3,  3);
	ROUND(H, d, a, b, c, in[ 0] + K3,  9);
	ROUND(H, c, d, a, b, in[ 4] + K3, 11);
	ROUND(H, b, c, d, a, in[ 8] + K3, 15);

	return buf[1] + b; /* "most hashed" word */
	/* Alternative: return sum of all words? */
}
#endif

#undef ROUND
#undef F
#undef G
#undef H
#undef K1
#undef K2
#undef K3

/* This should not be decreased so low that ISNs wrap too fast. */
#define REKEY_INTERVAL (300 * HZ)
/*
 * Bit layout of the tcp sequence numbers (before adding current time):
 * bit 24-31: increased after every key exchange
 * bit 0-23: hash(source,dest)
 *
 * The implementation is similar to the algorithm described
 * in the Appendix of RFC 1185, except that
 * - it uses a 1 MHz clock instead of a 250 kHz clock
 * - it performs a rekey every 5 minutes, which is equivalent
 * 	to a (source,dest) tulple dependent forward jump of the
 * 	clock by 0..2^(HASH_BITS+1)
 *
 * Thus the average ISN wraparound time is 68 minutes instead of
 * 4.55 hours.
 *
 * SMP cleanup and lock avoidance with poor man's RCU.
 * 			Manfred Spraul <manfred@colorfullife.com>
 *
 */
#define COUNT_BITS 8
#define COUNT_MASK ((1 << COUNT_BITS) - 1)
#define HASH_BITS 24
#define HASH_MASK ((1 << HASH_BITS) - 1)

static struct keydata {
	__u32 count; /* already shifted to the final position */
	__u32 secret[12];
} ____cacheline_aligned ip_keydata[2];

static unsigned int ip_cnt;

static void rekey_seq_generator(void *private_);

static DECLARE_WORK(rekey_work, rekey_seq_generator, NULL);

/*
 * Lock avoidance:
 * The ISN generation runs lockless - it's just a hash over random data.
 * State changes happen every 5 minutes when the random key is replaced.
 * Synchronization is performed by having two copies of the hash function
 * state and rekey_seq_generator always updates the inactive copy.
 * The copy is then activated by updating ip_cnt.
 * The implementation breaks down if someone blocks the thread
 * that processes SYN requests for more than 5 minutes. Should never
 * happen, and even if that happens only a not perfectly compliant
 * ISN is generated, nothing fatal.
 */
static void rekey_seq_generator(void *private_)
{
	struct keydata *keyptr = &ip_keydata[1 ^ (ip_cnt & 1)];

	get_random_bytes(keyptr->secret, sizeof(keyptr->secret));
	keyptr->count = (ip_cnt & COUNT_MASK) << HASH_BITS;
	smp_wmb();
	ip_cnt++;
	schedule_delayed_work(&rekey_work, REKEY_INTERVAL);
}

static inline struct keydata *get_keyptr(void)
{
	struct keydata *keyptr = &ip_keydata[ip_cnt & 1];

	smp_rmb();

	return keyptr;
}

static __init int seqgen_init(void)
{
	rekey_seq_generator(NULL);
	return 0;
}
late_initcall(seqgen_init);

#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
__u32 secure_tcpv6_sequence_number(__u32 *saddr, __u32 *daddr,
				   __u16 sport, __u16 dport)
{
	struct timeval tv;
	__u32 seq;
	__u32 hash[12];
	struct keydata *keyptr = get_keyptr();

	/* The procedure is the same as for IPv4, but addresses are longer.
	 * Thus we must use twothirdsMD4Transform.
	 */

	memcpy(hash, saddr, 16);
	hash[4]=(sport << 16) + dport;
	memcpy(&hash[5],keyptr->secret,sizeof(__u32) * 7);

	seq = twothirdsMD4Transform(daddr, hash) & HASH_MASK;
	seq += keyptr->count;

	do_gettimeofday(&tv);
	seq += tv.tv_usec + tv.tv_sec * 1000000;

	return seq;
}
EXPORT_SYMBOL(secure_tcpv6_sequence_number);
#endif

__u32 secure_tcp_sequence_number(__u32 saddr, __u32 daddr,
				 __u16 sport, __u16 dport)
{
	struct timeval tv;
	__u32 seq;
	__u32 hash[4];
	struct keydata *keyptr = get_keyptr();

	/*
	 *  Pick a unique starting offset for each TCP connection endpoints
	 *  (saddr, daddr, sport, dport).
	 *  Note that the words are placed into the starting vector, which is
	 *  then mixed with a partial MD4 over random data.
	 */
	hash[0]=saddr;
	hash[1]=daddr;
	hash[2]=(sport << 16) + dport;
	hash[3]=keyptr->secret[11];

	seq = halfMD4Transform(hash, keyptr->secret) & HASH_MASK;
	seq += keyptr->count;
	/*
	 *	As close as possible to RFC 793, which
	 *	suggests using a 250 kHz clock.
	 *	Further reading shows this assumes 2 Mb/s networks.
	 *	For 10 Mb/s Ethernet, a 1 MHz clock is appropriate.
	 *	That's funny, Linux has one built in!  Use it!
	 *	(Networks are faster now - should this be increased?)
	 */
	do_gettimeofday(&tv);
	seq += tv.tv_usec + tv.tv_sec * 1000000;
#if 0
	printk("init_seq(%lx, %lx, %d, %d) = %d\n",
	       saddr, daddr, sport, dport, seq);
#endif
	return seq;
}

EXPORT_SYMBOL(secure_tcp_sequence_number);

/*  The code below is shamelessly stolen from secure_tcp_sequence_number().
 *  All blames to Andrey V. Savochkin <saw@msu.ru>.
 */
__u32 secure_ip_id(__u32 daddr)
{
	struct keydata *keyptr;
	__u32 hash[4];

	keyptr = get_keyptr();

	/*
	 *  Pick a unique starting offset for each IP destination.
	 *  The dest ip address is placed in the starting vector,
	 *  which is then hashed with random data.
	 */
	hash[0] = daddr;
	hash[1] = keyptr->secret[9];
	hash[2] = keyptr->secret[10];
	hash[3] = keyptr->secret[11];

	return halfMD4Transform(hash, keyptr->secret);
}

/* Generate secure starting point for ephemeral TCP port search */
u32 secure_tcp_port_ephemeral(__u32 saddr, __u32 daddr, __u16 dport)
{
	struct keydata *keyptr = get_keyptr();
	u32 hash[4];

	/*
	 *  Pick a unique starting offset for each ephemeral port search
	 *  (saddr, daddr, dport) and 48bits of random data.
	 */
	hash[0] = saddr;
	hash[1] = daddr;
	hash[2] = dport ^ keyptr->secret[10];
	hash[3] = keyptr->secret[11];

	return halfMD4Transform(hash, keyptr->secret);
}

#ifdef CONFIG_SYN_COOKIES
/*
 * Secure SYN cookie computation. This is the algorithm worked out by
 * Dan Bernstein and Eric Schenk.
 *
 * For linux I implement the 1 minute counter by looking at the jiffies clock.
 * The count is passed in as a parameter, so this code doesn't much care.
 */

#define COOKIEBITS 24	/* Upper bits store count */
#define COOKIEMASK (((__u32)1 << COOKIEBITS) - 1)

static int syncookie_init;
static __u32 syncookie_secret[2][16-3+HASH_BUFFER_SIZE];

__u32 secure_tcp_syn_cookie(__u32 saddr, __u32 daddr, __u16 sport,
		__u16 dport, __u32 sseq, __u32 count, __u32 data)
{
	__u32 tmp[16 + HASH_BUFFER_SIZE + HASH_EXTRA_SIZE];
	__u32 seq;

	/*
	 * Pick two random secrets the first time we need a cookie.
	 */
	if (syncookie_init == 0) {
		get_random_bytes(syncookie_secret, sizeof(syncookie_secret));
		syncookie_init = 1;
	}

	/*
	 * Compute the secure sequence number.
	 * The output should be:
   	 *   HASH(sec1,saddr,sport,daddr,dport,sec1) + sseq + (count * 2^24)
	 *      + (HASH(sec2,saddr,sport,daddr,dport,count,sec2) % 2^24).
	 * Where sseq is their sequence number and count increases every
	 * minute by 1.
	 * As an extra hack, we add a small "data" value that encodes the
	 * MSS into the second hash value.
	 */

	memcpy(tmp + 3, syncookie_secret[0], sizeof(syncookie_secret[0]));
	tmp[0]=saddr;
	tmp[1]=daddr;
	tmp[2]=(sport << 16) + dport;
	HASH_TRANSFORM(tmp+16, tmp);
	seq = tmp[17] + sseq + (count << COOKIEBITS);

	memcpy(tmp + 3, syncookie_secret[1], sizeof(syncookie_secret[1]));
	tmp[0]=saddr;
	tmp[1]=daddr;
	tmp[2]=(sport << 16) + dport;
	tmp[3] = count;	/* minute counter */
	HASH_TRANSFORM(tmp + 16, tmp);

	/* Add in the second hash and the data */
	return seq + ((tmp[17] + data) & COOKIEMASK);
}

/*
 * This retrieves the small "data" value from the syncookie.
 * If the syncookie is bad, the data returned will be out of
 * range.  This must be checked by the caller.
 *
 * The count value used to generate the cookie must be within
 * "maxdiff" if the current (passed-in) "count".  The return value
 * is (__u32)-1 if this test fails.
 */
__u32 check_tcp_syn_cookie(__u32 cookie, __u32 saddr, __u32 daddr, __u16 sport,
		__u16 dport, __u32 sseq, __u32 count, __u32 maxdiff)
{
	__u32 tmp[16 + HASH_BUFFER_SIZE + HASH_EXTRA_SIZE];
	__u32 diff;

	if (syncookie_init == 0)
		return (__u32)-1; /* Well, duh! */

	/* Strip away the layers from the cookie */
	memcpy(tmp + 3, syncookie_secret[0], sizeof(syncookie_secret[0]));
	tmp[0]=saddr;
	tmp[1]=daddr;
	tmp[2]=(sport << 16) + dport;
	HASH_TRANSFORM(tmp + 16, tmp);
	cookie -= tmp[17] + sseq;
	/* Cookie is now reduced to (count * 2^24) ^ (hash % 2^24) */

	diff = (count - (cookie >> COOKIEBITS)) & ((__u32)-1 >> COOKIEBITS);
	if (diff >= maxdiff)
		return (__u32)-1;

	memcpy(tmp+3, syncookie_secret[1], sizeof(syncookie_secret[1]));
	tmp[0] = saddr;
	tmp[1] = daddr;
	tmp[2] = (sport << 16) + dport;
	tmp[3] = count - diff;	/* minute counter */
	HASH_TRANSFORM(tmp + 16, tmp);

	return (cookie - tmp[17]) & COOKIEMASK;	/* Leaving the data behind */
}
#endif
#endif /* CONFIG_INET */