diff options
Diffstat (limited to 'tools/plink/sshcrcda.c')
| -rw-r--r-- | tools/plink/sshcrcda.c | 172 |
1 files changed, 172 insertions, 0 deletions
diff --git a/tools/plink/sshcrcda.c b/tools/plink/sshcrcda.c new file mode 100644 index 000000000..c2cf705b2 --- /dev/null +++ b/tools/plink/sshcrcda.c @@ -0,0 +1,172 @@ +/* $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"
+
+typedef unsigned char uchar;
+typedef unsigned short uint16;
+
+/* SSH Constants */
+#define SSH_MAXBLOCKS (32 * 1024)
+#define SSH_BLOCKSIZE (8)
+
+/* Hashing constants */
+#define HASH_MINSIZE (8 * 1024)
+#define HASH_ENTRYSIZE (sizeof(uint16))
+#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))
+
+uchar ONE[4] = { 1, 0, 0, 0 };
+uchar ZERO[4] = { 0, 0, 0, 0 };
+
+struct crcda_ctx {
+ uint16 *h;
+ uint32 n;
+};
+
+void *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(void *handle)
+{
+ struct crcda_ctx *ctx = (struct crcda_ctx *)handle;
+ if (ctx) {
+ sfree(ctx->h);
+ ctx->h = NULL;
+ sfree(ctx);
+ }
+}
+
+static void crc_update(uint32 *a, void *b)
+{
+ *a = crc32_update(*a, b, 4);
+}
+
+/* detect if a block is used in a particular pattern */
+static int check_crc(uchar *S, uchar *buf, uint32 len, uchar *IV)
+{
+ uint32 crc;
+ uchar *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 */
+int detect_attack(void *handle, uchar *buf, uint32 len, uchar *IV)
+{
+ struct crcda_ctx *ctx = (struct crcda_ctx *)handle;
+ register uint32 i, j;
+ uint32 l;
+ register uchar *c;
+ uchar *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);
+ } else {
+ if (l > ctx->n) {
+ ctx->n = l;
+ ctx->h = sresize(ctx->h, ctx->n, uint16);
+ }
+ }
+
+ 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 1; /* attack detected */
+ else
+ break;
+ }
+ for (d = buf; d < c; d += SSH_BLOCKSIZE) {
+ if (!CMP(c, d)) {
+ if ((check_crc(c, buf, len, IV)))
+ return 1; /* attack detected */
+ else
+ break;
+ }
+ }
+ }
+ return 0; /* 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) {
+ if (!CMP(c, IV)) {
+ if (check_crc(c, buf, len, IV))
+ return 1; /* attack detected */
+ else
+ break;
+ }
+ } else if (!CMP(c, buf + ctx->h[i] * SSH_BLOCKSIZE)) {
+ if (check_crc(c, buf, len, IV))
+ return 1; /* attack detected */
+ else
+ break;
+ }
+ }
+ ctx->h[i] = j;
+ }
+ return 0; /* ok */
+}
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