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From 5846e57538c750c5ce67df887d09fa99861c79c6 Mon Sep 17 00:00:00 2001
From: Jakub Jelen <jjelen@redhat.com>
Date: Thu, 14 Dec 2023 12:22:01 +0100
Subject: [PATCH] CVE-2023-48795: Strip extensions from both kex lists for
matching
Signed-off-by: Jakub Jelen <jjelen@redhat.com>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
Upstream-Status: Backport [https://gitlab.com/libssh/libssh-mirror/-/commit/5846e57538c750c5ce67df887d09fa99861c79c6]
CVE: CVE-2023-48795
Signed-off-by: Vijay Anusuri <vanusuri@mvista.com>
---
src/kex.c | 16 ++++++++++++----
1 file changed, 12 insertions(+), 4 deletions(-)
diff --git a/src/kex.c b/src/kex.c
index b03e6484..c100d908 100644
--- a/src/kex.c
+++ b/src/kex.c
@@ -857,11 +857,19 @@ int ssh_kex_select_methods (ssh_session session){
char *ext_start = NULL;
int i;
- /* Here we should drop the ext-info-c from the list so we avoid matching.
+ /* Here we should drop the extensions from the list so we avoid matching.
* it. We added it to the end, so we can just truncate the string here */
- ext_start = strstr(client->methods[SSH_KEX], ","KEX_EXTENSION_CLIENT);
- if (ext_start != NULL) {
- ext_start[0] = '\0';
+ if (session->client) {
+ ext_start = strstr(client->methods[SSH_KEX], "," KEX_EXTENSION_CLIENT);
+ if (ext_start != NULL) {
+ ext_start[0] = '\0';
+ }
+ }
+ if (session->server) {
+ ext_start = strstr(server->methods[SSH_KEX], "," KEX_STRICT_SERVER);
+ if (ext_start != NULL) {
+ ext_start[0] = '\0';
+ }
}
for (i = 0; i < KEX_METHODS_SIZE; i++) {
--
2.25.1
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