diff options
Diffstat (limited to 'sshcrcda.c')
| -rw-r--r-- | sshcrcda.c | 171 |
1 files changed, 0 insertions, 171 deletions
diff --git a/sshcrcda.c b/sshcrcda.c deleted file mode 100644 index 18044754..00000000 --- a/sshcrcda.c +++ /dev/null @@ -1,171 +0,0 @@ -/* $OpenBSD: deattack.c,v 1.14 2001/06/23 15:12:18 itojun Exp $ */ - -/* - * Cryptographic attack detector for ssh - source code - * - * Copyright (c) 1998 CORE SDI S.A., Buenos Aires, Argentina. - * - * All rights reserved. Redistribution and use in source and binary - * forms, with or without modification, are permitted provided that - * this copyright notice is retained. - * - * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED - * WARRANTIES ARE DISCLAIMED. IN NO EVENT SHALL CORE SDI S.A. BE - * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY OR - * CONSEQUENTIAL DAMAGES RESULTING FROM THE USE OR MISUSE OF THIS - * SOFTWARE. - * - * Ariel Futoransky <futo@core-sdi.com> - * <http://www.core-sdi.com> - * - * Modified for use in PuTTY by Simon Tatham - */ - -#include <assert.h> -#include "misc.h" -#include "ssh.h" - -/* SSH Constants */ -#define SSH_MAXBLOCKS (32 * 1024) -#define SSH_BLOCKSIZE (8) - -/* Hashing constants */ -#define HASH_MINSIZE (8 * 1024) -#define HASH_ENTRYSIZE (sizeof(uint16_t)) -#define HASH_FACTOR(x) ((x)*3/2) -#define HASH_UNUSEDCHAR (0xff) -#define HASH_UNUSED (0xffff) -#define HASH_IV (0xfffe) - -#define HASH_MINBLOCKS (7*SSH_BLOCKSIZE) - -/* Hash function (Input keys are cipher results) */ -#define HASH(x) GET_32BIT_MSB_FIRST(x) - -#define CMP(a, b) (memcmp(a, b, SSH_BLOCKSIZE)) - -static const uint8_t ONE[4] = { 1, 0, 0, 0 }; -static const uint8_t ZERO[4] = { 0, 0, 0, 0 }; - -struct crcda_ctx { - uint16_t *h; - uint32_t n; -}; - -struct crcda_ctx *crcda_make_context(void) -{ - struct crcda_ctx *ret = snew(struct crcda_ctx); - ret->h = NULL; - ret->n = HASH_MINSIZE / HASH_ENTRYSIZE; - return ret; -} - -void crcda_free_context(struct crcda_ctx *ctx) -{ - if (ctx) { - sfree(ctx->h); - ctx->h = NULL; - sfree(ctx); - } -} - -static void crc_update(uint32_t *a, const void *b) -{ - *a = crc32_update(*a, make_ptrlen(b, 4)); -} - -/* detect if a block is used in a particular pattern */ -static bool check_crc(const uint8_t *S, const uint8_t *buf, - uint32_t len, const uint8_t *IV) -{ - uint32_t crc; - const uint8_t *c; - - crc = 0; - if (IV && !CMP(S, IV)) { - crc_update(&crc, ONE); - crc_update(&crc, ZERO); - } - for (c = buf; c < buf + len; c += SSH_BLOCKSIZE) { - if (!CMP(S, c)) { - crc_update(&crc, ONE); - crc_update(&crc, ZERO); - } else { - crc_update(&crc, ZERO); - crc_update(&crc, ZERO); - } - } - return (crc == 0); -} - -/* Detect a crc32 compensation attack on a packet */ -bool detect_attack(struct crcda_ctx *ctx, - const unsigned char *buf, uint32_t len, - const unsigned char *IV) -{ - register uint32_t i, j; - uint32_t l; - register const uint8_t *c; - const uint8_t *d; - - assert(!(len > (SSH_MAXBLOCKS * SSH_BLOCKSIZE) || - len % SSH_BLOCKSIZE != 0)); - for (l = ctx->n; l < HASH_FACTOR(len / SSH_BLOCKSIZE); l = l << 2) - ; - - if (ctx->h == NULL) { - ctx->n = l; - ctx->h = snewn(ctx->n, uint16_t); - } else { - if (l > ctx->n) { - ctx->n = l; - ctx->h = sresize(ctx->h, ctx->n, uint16_t); - } - } - - if (len <= HASH_MINBLOCKS) { - for (c = buf; c < buf + len; c += SSH_BLOCKSIZE) { - if (IV && (!CMP(c, IV))) { - if ((check_crc(c, buf, len, IV))) - return true; /* attack detected */ - else - break; - } - for (d = buf; d < c; d += SSH_BLOCKSIZE) { - if (!CMP(c, d)) { - if ((check_crc(c, buf, len, IV))) - return true; /* attack detected */ - else - break; - } - } - } - return false; /* ok */ - } - memset(ctx->h, HASH_UNUSEDCHAR, ctx->n * HASH_ENTRYSIZE); - - if (IV) - ctx->h[HASH(IV) & (ctx->n - 1)] = HASH_IV; - - for (c = buf, j = 0; c < (buf + len); c += SSH_BLOCKSIZE, j++) { - for (i = HASH(c) & (ctx->n - 1); ctx->h[i] != HASH_UNUSED; - i = (i + 1) & (ctx->n - 1)) { - if (ctx->h[i] == HASH_IV) { - assert(IV); /* or we wouldn't have stored HASH_IV above */ - if (!CMP(c, IV)) { - if (check_crc(c, buf, len, IV)) - return true; /* attack detected */ - else - break; - } - } else if (!CMP(c, buf + ctx->h[i] * SSH_BLOCKSIZE)) { - if (check_crc(c, buf, len, IV)) - return true; /* attack detected */ - else - break; - } - } - ctx->h[i] = j; - } - return false; /* ok */ -} |