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Fix CVE-2026-35387

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Fix incomplete application of PubkeyAcceptedAlgorithms
and HostbasedAcceptedAlgorithms with regard to ECDSA keys

Resolves: RHEL-166235

Signed-off-by: Zoltan Fridrich <zfridric@redhat.com>
This commit is contained in:
Zoltan Fridrich 2026-04-14 10:42:30 +02:00
parent 543ad4010f
commit 99fe8be9db
2 changed files with 109 additions and 0 deletions
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103
openssh-9.9p1-ecdsa-incomplete-application.patch Normal file
View File

@ -0,0 +1,103 @@
diff --color -ruNp a/auth2-hostbased.c b/auth2-hostbased.c
--- a/auth2-hostbased.c 2026-04-09 13:22:28.114045749 +0200
+++ b/auth2-hostbased.c 2026-04-09 14:34:44.876393822 +0200
@@ -96,9 +96,10 @@ userauth_hostbased(struct ssh *ssh, cons
error_f("cannot decode key: %s", pkalg);
goto done;
}
- if (key->type != pktype) {
- error_f("type mismatch for decoded key "
- "(received %d, expected %d)", key->type, pktype);
+ if (key->type != pktype || (sshkey_type_plain(pktype) == KEY_ECDSA &&
+ sshkey_ecdsa_nid_from_name(pkalg) != key->ecdsa_nid)) {
+ error_f("key type mismatch for decoded key "
+ "(received %s, expected %s)", sshkey_ssh_name(key), pkalg);
goto done;
}
if (match_pattern_list(pkalg, options.hostbased_accepted_algos, 0) != 1) {
diff --color -ruNp a/auth2-pubkey.c b/auth2-pubkey.c
--- a/auth2-pubkey.c 2026-04-09 13:22:28.157194118 +0200
+++ b/auth2-pubkey.c 2026-04-09 14:35:48.997689347 +0200
@@ -152,9 +152,10 @@ userauth_pubkey(struct ssh *ssh, const c
error_f("cannot decode key: %s", pkalg);
goto done;
}
- if (key->type != pktype) {
- error_f("type mismatch for decoded key "
- "(received %d, expected %d)", key->type, pktype);
+ if (key->type != pktype || (sshkey_type_plain(pktype) == KEY_ECDSA &&
+ sshkey_ecdsa_nid_from_name(pkalg) != key->ecdsa_nid)) {
+ error_f("key type mismatch for decoded key "
+ "(received %s, expected %s)", sshkey_ssh_name(key), pkalg);
goto done;
}
if (auth2_key_already_used(authctxt, key)) {
diff --color -ruNp a/sshconnect2.c b/sshconnect2.c
--- a/sshconnect2.c 2026-04-09 13:22:28.193412553 +0200
+++ b/sshconnect2.c 2026-04-09 14:42:37.644945762 +0200
@@ -91,6 +91,7 @@ extern Options options;
static char *xxx_host;
static struct sockaddr *xxx_hostaddr;
static const struct ssh_conn_info *xxx_conn_info;
+static int key_type_allowed(struct sshkey *, const char *);
static int
verify_host_key_callback(struct sshkey *hostkey, struct ssh *ssh)
@@ -100,6 +101,10 @@ verify_host_key_callback(struct sshkey *
if ((r = sshkey_check_rsa_length(hostkey,
options.required_rsa_size)) != 0)
fatal_r(r, "Bad server host key");
+ if (!key_type_allowed(hostkey, options.hostkeyalgorithms)) {
+ fatal("Server host key %s not in HostKeyAlgorithms",
+ sshkey_ssh_name(hostkey));
+ }
if (verify_host_key(xxx_host, xxx_hostaddr, hostkey,
xxx_conn_info) != 0)
fatal("Host key verification failed.");
@@ -1776,34 +1781,37 @@ load_identity_file(Identity *id)
}
static int
-key_type_allowed_by_config(struct sshkey *key)
+key_type_allowed(struct sshkey *key, const char *allowlist)
{
- if (match_pattern_list(sshkey_ssh_name(key),
- options.pubkey_accepted_algos, 0) == 1)
+ if (match_pattern_list(sshkey_ssh_name(key), allowlist, 0) == 1)
return 1;
/* RSA keys/certs might be allowed by alternate signature types */
switch (key->type) {
case KEY_RSA:
- if (match_pattern_list("rsa-sha2-512",
- options.pubkey_accepted_algos, 0) == 1)
+ if (match_pattern_list("rsa-sha2-512", allowlist, 0) == 1)
return 1;
- if (match_pattern_list("rsa-sha2-256",
- options.pubkey_accepted_algos, 0) == 1)
+ if (match_pattern_list("rsa-sha2-256", allowlist, 0) == 1)
return 1;
break;
case KEY_RSA_CERT:
if (match_pattern_list("rsa-sha2-512-cert-v01@openssh.com",
- options.pubkey_accepted_algos, 0) == 1)
+ allowlist, 0) == 1)
return 1;
if (match_pattern_list("rsa-sha2-256-cert-v01@openssh.com",
- options.pubkey_accepted_algos, 0) == 1)
+ allowlist, 0) == 1)
return 1;
break;
}
return 0;
}
+static int
+key_type_allowed_by_config(struct sshkey *key)
+{
+ return key_type_allowed(key, options.pubkey_accepted_algos);
+}
+
/* obtain a list of keys from the agent */
static int
get_agent_identities(struct ssh *ssh, int *agent_fdp,

6
openssh.spec
View File

@ -253,6 +253,8 @@ Patch1040: openssh-9.9p1-fill-default-options-error.patch
Patch1041: openssh-9.9p1-scp-clear-setuid.patch
# upstream c805b97b67c774e0bf922ffb29dfbcda9d7b5add
Patch1042: openssh-9.9p1-mux-askpass-check.patch
# upstream fd1c7e131f331942d20f42f31e79912d570081fa
Patch1043: openssh-9.9p1-ecdsa-incomplete-application.patch
License: BSD
Requires: /sbin/nologin
@ -469,6 +471,7 @@ popd
%patch1040 -p1 -b .fill-default-options-error
%patch1041 -p1 -b .scp-clear-setuid
%patch1042 -p1 -b .mux-askpass-check
%patch1043 -p1 -b .ecdsa-incomplete-application
%patch100 -p1 -b .coverity
@ -770,6 +773,9 @@ test -f %{sysconfig_anaconda} && \
- CVE-2026-35388: Add connection multiplexing confirmation for proxy-mode
multiplexing sessions
Resolves: RHEL-166251
- CVE-2026-35387: Fix incomplete application of PubkeyAcceptedAlgorithms
and HostbasedAcceptedAlgorithms with regard to ECDSA keys
Resolves: RHEL-166235
* Thu Mar 26 2026 Zoltan Fridrich <zfridric@redhat.com> - 9.9p1-7 + 0.10.4-9
- Version bump