nhyatt/putty-source
1
0
Fork 0
mirror of https://git.tartarus.org/simon/putty.git synced 2025-01-09 17:38:00 +00:00
Code Issues Projects Releases Wiki Activity

Fix potential segfaults in reading OpenSSH's ASN.1 key format.

Browse Source 
The length coming back from ber_read_id_len might have overflowed, so
treat it as potentially negative. Also, while I'm here, accumulate it
inside ber_read_id_len as an unsigned, so as to avoid undefined
behaviour on integer overflow, and toint() it before return.

Thanks to Hanno Böck for spotting this, with the aid of AFL.

(cherry picked from commit 5b7833cd47)

Conflicts:
	import.c

(cherry-picker's note: resolving the conflict involved removing an
entire section of the original commit which fixed ECDSA code not
present on this branch)
This commit is contained in:
Simon Tatham 2016-02-25 20:26:33 +00:00
parent cac650b8a5
commit f0222e7464
1 changed files with 7 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
import.c
View File

@ -176,14 +176,16 @@ static int ber_read_id_len(void *source, int sourcelen,
return -1;
if (*p & 0x80) {
unsigned len;
int n = *p & 0x7F;
p++, sourcelen--;
if (sourcelen < n)
return -1;
*length = 0;
len = 0;
while (n--)
*length = (*length << 8) | (*p++);
len = (len << 8) | (*p++);
sourcelen -= n;
*length = toint(len);
} else {
*length = *p;
p++, sourcelen--;
@ -599,7 +601,8 @@ struct ssh2_userkey *openssh_read(const Filename *filename, char *passphrase,
* decrypt, if the key was encrypted. */
ret = ber_read_id_len(p, key->keyblob_len, &id, &len, &flags);
p += ret;
if (ret < 0 || id != 16) {
if (ret < 0 || id != 16 || len < 0 ||
key->keyblob+key->keyblob_len-p < len) {
errmsg = "ASN.1 decoding failure";
retval = key->encrypted ? SSH2_WRONG_PASSPHRASE : NULL;
goto error;
@ -630,7 +633,7 @@ struct ssh2_userkey *openssh_read(const Filename *filename, char *passphrase,
ret = ber_read_id_len(p, key->keyblob+key->keyblob_len-p,
&id, &len, &flags);
p += ret;
if (ret < 0 || id != 2 ||
if (ret < 0 || id != 2 || len < 0 ||
key->keyblob+key->keyblob_len-p < len) {
errmsg = "ASN.1 decoding failure";
retval = key->encrypted ? SSH2_WRONG_PASSPHRASE : NULL;