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client: Handle the MSG_EXT_INFO packet signalling supported extensions

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RFC 8308: The extension negotiation in Secure Shell (SSH) Protocol

RFC 8332: Use of RSA Keys with SHA-256 and SHA-512
          in the Secure Shell (SSH) Protocol

Signed-off-by: Jakub Jelen <jjelen@redhat.com>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
This commit is contained in:
Jakub Jelen
2018-08-06 11:51:26 +02:00
committed by Andreas Schneider
parent df13d8c61f
commit 761225712a
5 changed files with 65 additions and 2 deletions
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52
src/packet_cb.c
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@@ -270,3 +270,55 @@ SSH_PACKET_CALLBACK(ssh_packet_service_accept){
return SSH_PACKET_USED;
}
/**
* @internal
* @brief handles a SSH2_MSG_EXT_INFO packet defined in RFC 8308
*
*/
SSH_PACKET_CALLBACK(ssh_packet_ext_info)
{
int rc;
uint32_t nr_extensions = 0;
uint32_t i;
(void)type;
(void)user;
SSH_LOG(SSH_LOG_PACKET, "Received SSH_MSG_EXT_INFO");
rc = ssh_buffer_get_u32(packet, &nr_extensions);
if (rc == 0) {
SSH_LOG(SSH_LOG_PACKET, "Failed to read number of extensions");
return SSH_PACKET_USED;
}
nr_extensions = ntohl(nr_extensions);
SSH_LOG(SSH_LOG_PACKET, "Follows %u extensions", nr_extensions);
for (i = 0; i < nr_extensions; i++) {
char *name = NULL;
char *value = NULL;
int cmp;
rc = ssh_buffer_unpack(packet, "ss", &name, &value);
if (rc != SSH_OK) {
SSH_LOG(SSH_LOG_PACKET, "Error reading extension name-value pair");
return SSH_PACKET_USED;
}
cmp = strcmp(name, "server-sig-algs");
if (cmp == 0) {
/* TODO check for NULL bytes */
SSH_LOG(SSH_LOG_PACKET, "Extension: %s=<%s>", name, value);
if (ssh_match_group(value, "rsa-sha2-512")) {
session->extensions |= SSH_EXT_SIG_RSA_SHA512;
}
if (ssh_match_group(value, "rsa-sha2-256")) {
session->extensions |= SSH_EXT_SIG_RSA_SHA256;
}
}
free(name);
free(value);
}
return SSH_PACKET_USED;
}