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Diffstat (limited to 'src/libfreeswan/prng.c')
| -rw-r--r-- | src/libfreeswan/prng.c | 200 |
1 files changed, 200 insertions, 0 deletions
diff --git a/src/libfreeswan/prng.c b/src/libfreeswan/prng.c new file mode 100644 index 000000000..347f13f89 --- /dev/null +++ b/src/libfreeswan/prng.c @@ -0,0 +1,200 @@ +/* + * crypto-class pseudorandom number generator + * currently uses same algorithm as RC4(TM), from Schneier 2nd ed p397 + * Copyright (C) 2002 Henry Spencer. + * + * This library is free software; you can redistribute it and/or modify it + * under the terms of the GNU Library General Public License as published by + * the Free Software Foundation; either version 2 of the License, or (at your + * option) any later version. See <http://www.fsf.org/copyleft/lgpl.txt>. + * + * This library is distributed in the hope that it will be useful, but + * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY + * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public + * License for more details. + */ +#include "internal.h" +#include "freeswan.h" + +/* + - prng_init - initialize PRNG from a key + */ +void +prng_init(prng, key, keylen) +struct prng *prng; +const unsigned char *key; +size_t keylen; +{ + unsigned char k[256]; + int i, j; + unsigned const char *p; + unsigned const char *keyend = key + keylen; + unsigned char t; + + for (i = 0; i <= 255; i++) + prng->sbox[i] = i; + p = key; + for (i = 0; i <= 255; i++) { + k[i] = *p++; + if (p >= keyend) + p = key; + } + j = 0; + for (i = 0; i <= 255; i++) { + j = (j + prng->sbox[i] + k[i]) & 0xff; + t = prng->sbox[i]; + prng->sbox[i] = prng->sbox[j]; + prng->sbox[j] = t; + k[i] = 0; /* clear out key memory */ + } + prng->i = 0; + prng->j = 0; + prng->count = 0; +} + +/* + - prng_bytes - get some pseudorandom bytes from PRNG + */ +void +prng_bytes(prng, dst, dstlen) +struct prng *prng; +unsigned char *dst; +size_t dstlen; +{ + int i, j, t; + unsigned char *p = dst; + size_t remain = dstlen; +# define MAX 4000000000ul + + while (remain > 0) { + i = (prng->i + 1) & 0xff; + prng->i = i; + j = (prng->j + prng->sbox[i]) & 0xff; + prng->j = j; + t = prng->sbox[i]; + prng->sbox[i] = prng->sbox[j]; + prng->sbox[j] = t; + t = (t + prng->sbox[i]) & 0xff; + *p++ = prng->sbox[t]; + remain--; + } + if (prng->count < MAX - dstlen) + prng->count += dstlen; + else + prng->count = MAX; +} + +/* + - prnt_count - how many bytes have been extracted from PRNG so far? + */ +unsigned long +prng_count(prng) +struct prng *prng; +{ + return prng->count; +} + +/* + - prng_final - clear out PRNG to ensure nothing left in memory + */ +void +prng_final(prng) +struct prng *prng; +{ + int i; + + for (i = 0; i <= 255; i++) + prng->sbox[i] = 0; + prng->i = 0; + prng->j = 0; + prng->count = 0; /* just for good measure */ +} + + + +#ifdef PRNG_MAIN + +#include <stdio.h> + +void regress(); + +int +main(argc, argv) +int argc; +char *argv[]; +{ + struct prng pr; + unsigned char buf[100]; + unsigned char *p; + size_t n; + + if (argc < 2) { + fprintf(stderr, "Usage: %s {key|-r}\n", argv[0]); + exit(2); + } + + if (strcmp(argv[1], "-r") == 0) { + regress(); + fprintf(stderr, "regress() returned?!?\n"); + exit(1); + } + + prng_init(&pr, argv[1], strlen(argv[1])); + prng_bytes(&pr, buf, 32); + printf("0x"); + for (p = buf, n = 32; n > 0; p++, n--) + printf("%02x", *p); + printf("\n%lu bytes\n", prng_count(&pr)); + prng_final(&pr); + exit(0); +} + +void +regress() +{ + struct prng pr; + unsigned char buf[100]; + unsigned char *p; + size_t n; + /* somewhat non-random sample key */ + unsigned char key[] = "here we go gathering nuts in May"; + /* first thirty bytes of output from that key */ + unsigned char good[] = "\x3f\x02\x8e\x4a\x2a\xea\x23\x18\x92\x7c" + "\x09\x52\x83\x61\xaa\x26\xce\xbb\x9d\x71" + "\x71\xe5\x10\x22\xaf\x60\x54\x8d\x5b\x28"; + int nzero, none; + int show = 0; + + prng_init(&pr, key, strlen(key)); + prng_bytes(&pr, buf, sizeof(buf)); + for (p = buf, n = sizeof(buf); n > 0; p++, n--) { + if (*p == 0) + nzero++; + if (*p == 255) + none++; + } + if (nzero > 3 || none > 3) { + fprintf(stderr, "suspiciously non-random output!\n"); + show = 1; + } + if (memcmp(buf, good, strlen(good)) != 0) { + fprintf(stderr, "incorrect output!\n"); + show = 1; + } + if (show) { + fprintf(stderr, "0x"); + for (p = buf, n = sizeof(buf); n > 0; p++, n--) + fprintf(stderr, "%02x", *p); + fprintf(stderr, "\n"); + exit(1); + } + if (prng_count(&pr) != sizeof(buf)) { + fprintf(stderr, "got %u bytes, but count is %lu\n", + sizeof(buf), prng_count(&pr)); + exit(1); + } + prng_final(&pr); + exit(0); +} + +#endif /* PRNG_MAIN */ |