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Dimitry Andric spotted that DH gex with SHA-256 was overflowing a buffer.

Browse Source 
Fixed, and added paranoia so that this shouldn't happen again.

[originally from svn r6606]
[this svn revision also touched putty-wishlist]
This commit is contained in:
Jacob Nevins 2006-03-12 19:24:05 +00:00
parent 2cf27e43bb
commit 078c516a45
2 changed files with 27 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

29
ssh.c
View File

@ -708,7 +708,7 @@ struct ssh_tag {
void *cs_comp_ctx, *sc_comp_ctx;
const struct ssh_kex *kex;
const struct ssh_signkey *hostkey;
unsigned char v2_session_id[32];
unsigned char v2_session_id[SSH2_KEX_MAX_HASH_LEN];
int v2_session_id_len;
void *kex_ctx;
@ -4964,7 +4964,10 @@ static int first_in_commasep_string(char *needle, char *haystack, int haylen)
/*
* SSH-2 key creation method.
* (Currently assumes 2 lots of any hash are sufficient to generate
* keys/IVs for any cipher/MAC. SSH2_MKKEY_ITERS documents this assumption.)
*/
#define SSH2_MKKEY_ITERS (2)
static void ssh2_mkkey(Ssh ssh, Bignum K, unsigned char *H, char chr,
unsigned char *keyspace)
{
@ -5011,7 +5014,7 @@ static int do_ssh2_transport(Ssh ssh, void *vin, int inlen,
char *hostkeydata, *sigdata, *keystr, *fingerprint;
int hostkeylen, siglen;
void *hkey; /* actual host key */
unsigned char exchange_hash[32];
unsigned char exchange_hash[SSH2_KEX_MAX_HASH_LEN];
int n_preferred_kex;
const struct ssh_kexes *preferred_kex[KEX_MAX];
int n_preferred_ciphers;
@ -5064,7 +5067,7 @@ static int do_ssh2_transport(Ssh ssh, void *vin, int inlen,
s->preferred_kex[s->n_preferred_kex++] =
&ssh_diffiehellman_group1;
break;
case CIPHER_WARN:
case KEX_WARN:
/* Flag for later. Don't bother if it's the last in
* the list. */
if (i < KEX_MAX - 1) {
@ -5662,13 +5665,21 @@ static int do_ssh2_transport(Ssh ssh, void *vin, int inlen,
* hash from the _first_ key exchange.
*/
{
unsigned char keyspace[40];
unsigned char keyspace[SSH2_KEX_MAX_HASH_LEN * SSH2_MKKEY_ITERS];
assert(sizeof(keyspace) >= ssh->kex->hash->hlen * SSH2_MKKEY_ITERS);
ssh2_mkkey(ssh,s->K,s->exchange_hash,'C',keyspace);
assert((ssh->cscipher->keylen+7) / 8 <=
ssh->kex->hash->hlen * SSH2_MKKEY_ITERS);
ssh->cscipher->setkey(ssh->cs_cipher_ctx, keyspace);
ssh2_mkkey(ssh,s->K,s->exchange_hash,'A',keyspace);
assert(ssh->cscipher->blksize <=
ssh->kex->hash->hlen * SSH2_MKKEY_ITERS);
ssh->cscipher->setiv(ssh->cs_cipher_ctx, keyspace);
ssh2_mkkey(ssh,s->K,s->exchange_hash,'E',keyspace);
assert(ssh->csmac->len <=
ssh->kex->hash->hlen * SSH2_MKKEY_ITERS);
ssh->csmac->setkey(ssh->cs_mac_ctx, keyspace);
memset(keyspace, 0, sizeof(keyspace));
}
logeventf(ssh, "Initialised %.200s client->server encryption",
@ -5720,13 +5731,21 @@ static int do_ssh2_transport(Ssh ssh, void *vin, int inlen,
* hash from the _first_ key exchange.
*/
{
unsigned char keyspace[40];
unsigned char keyspace[SSH2_KEX_MAX_HASH_LEN * SSH2_MKKEY_ITERS];
assert(sizeof(keyspace) >= ssh->kex->hash->hlen * SSH2_MKKEY_ITERS);
ssh2_mkkey(ssh,s->K,s->exchange_hash,'D',keyspace);
assert((ssh->sccipher->keylen+7) / 8 <=
ssh->kex->hash->hlen * SSH2_MKKEY_ITERS);
ssh->sccipher->setkey(ssh->sc_cipher_ctx, keyspace);
ssh2_mkkey(ssh,s->K,s->exchange_hash,'B',keyspace);
assert(ssh->sccipher->blksize <=
ssh->kex->hash->hlen * SSH2_MKKEY_ITERS);
ssh->sccipher->setiv(ssh->sc_cipher_ctx, keyspace);
ssh2_mkkey(ssh,s->K,s->exchange_hash,'F',keyspace);
assert(ssh->scmac->len <=
ssh->kex->hash->hlen * SSH2_MKKEY_ITERS);
ssh->scmac->setkey(ssh->sc_mac_ctx, keyspace);
memset(keyspace, 0, sizeof(keyspace));
}
logeventf(ssh, "Initialised %.200s server->client encryption",
ssh->sccipher->text_name);

3
ssh.h
View File

@ -252,6 +252,9 @@ struct ssh2_userkey {
char *comment; /* the key comment */
};
/* The maximum length of any hash algorithm used in kex. (bytes) */
#define SSH2_KEX_MAX_HASH_LEN (32) /* SHA-256 */
extern const struct ssh_cipher ssh_3des;
extern const struct ssh_cipher ssh_des;
extern const struct ssh_cipher ssh_blowfish_ssh1;