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Do not require that unknown EXT_INFO extension values not
contain \0 characters. This would cause fatal connection errors if an
implementation sent e.g. string-encoded sub-values inside a value.

Reported by Denis Bider; ok markus@

Upstream-ID: 030e10fdc605563c040244c4b4f1d8ae75811a5c
This commit is contained in:
djm@openbsd.org 2017-06-13 12:13:59 +00:00 committed by Damien Miller
parent 6026f48dfc
commit c948030d54
1 changed files with 13 additions and 5 deletions
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18
kex.c
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@ -1,4 +1,4 @@
/* $OpenBSD: kex.c,v 1.133 2017/05/30 14:23:52 markus Exp $ */ /* $OpenBSD: kex.c,v 1.134 2017/06/13 12:13:59 djm Exp $ */
/* /*
* Copyright (c) 2000, 2001 Markus Friedl. All rights reserved. * Copyright (c) 2000, 2001 Markus Friedl. All rights reserved.
* *
@ -378,7 +378,9 @@ kex_input_ext_info(int type, u_int32_t seq, struct ssh *ssh)
{ {
struct kex *kex = ssh->kex; struct kex *kex = ssh->kex;
u_int32_t i, ninfo; u_int32_t i, ninfo;
char *name, *val, *found; char *name, *found;
u_char *val;
size_t vlen;
int r; int r;
debug("SSH2_MSG_EXT_INFO received"); debug("SSH2_MSG_EXT_INFO received");
@ -388,12 +390,17 @@ kex_input_ext_info(int type, u_int32_t seq, struct ssh *ssh)
for (i = 0; i < ninfo; i++) { for (i = 0; i < ninfo; i++) {
if ((r = sshpkt_get_cstring(ssh, &name, NULL)) != 0) if ((r = sshpkt_get_cstring(ssh, &name, NULL)) != 0)
return r; return r;
if ((r = sshpkt_get_cstring(ssh, &val, NULL)) != 0) { if ((r = sshpkt_get_string(ssh, &val, &vlen)) != 0) {
free(name); free(name);
return r; return r;
} }
debug("%s: %s=<%s>", __func__, name, val);
if (strcmp(name, "server-sig-algs") == 0) { if (strcmp(name, "server-sig-algs") == 0) {
/* Ensure no \0 lurking in value */
if (memchr(val, '\0', vlen) != NULL) {
error("%s: nul byte in %s", __func__, name);
return SSH_ERR_INVALID_FORMAT;
}
debug("%s: %s=<%s>", __func__, name, val);
found = match_list("rsa-sha2-256", val, NULL); found = match_list("rsa-sha2-256", val, NULL);
if (found) { if (found) {
kex->rsa_sha2 = 256; kex->rsa_sha2 = 256;
@ -404,7 +411,8 @@ kex_input_ext_info(int type, u_int32_t seq, struct ssh *ssh)
kex->rsa_sha2 = 512; kex->rsa_sha2 = 512;
free(found); free(found);
} }
} } else
debug("%s: %s (unrecognised)", __func__, name);
free(name); free(name);
free(val); free(val);
} }