microsoft · azurelinux-security · Jun 15, 2026
@@ -0,0 +1,170 @@
+From 6b2d525ff958ca55008a0728839be558f83d5f61 Mon Sep 17 00:00:00 2001
+From: AllSpark <allspark@microsoft.com>
+Date: Mon, 15 Jun 2026 06:47:26 +0000
+Subject: [PATCH] upstream: correctly match ECDSA signature algorithms against
+ allowlists
+
+Signed-off-by: Azure Linux Security Servicing Account <azurelinux-security@microsoft.com>
+Upstream-reference: AI Backport of https://github.com/openssh/openssh-portable/commit/fd1c7e131f331942d20f42f31e79912d570081fa.patch
+---
+ auth2-hostbased.c  |  7 ++++---
+ auth2-pubkey.c     |  7 ++++---
+ auth2-pubkeyfile.c | 24 ++++++++++++++----------
+ sshconnect2.c      | 26 +++++++++++++++++---------
+ 4 files changed, 39 insertions(+), 25 deletions(-)
+
+diff --git a/auth2-hostbased.c b/auth2-hostbased.c
+index 4022d92..cdf862f 100644
+--- a/auth2-hostbased.c
++++ b/auth2-hostbased.c
+@@ -96,9 +96,10 @@ userauth_hostbased(struct ssh *ssh, const char *method)
+ 		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 --git a/auth2-pubkey.c b/auth2-pubkey.c
+index 2a108ea..44090a4 100644
+--- a/auth2-pubkey.c
++++ b/auth2-pubkey.c
+@@ -149,9 +149,10 @@ userauth_pubkey(struct ssh *ssh, const char *method)
+ 		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 --git a/auth2-pubkeyfile.c b/auth2-pubkeyfile.c
+index 556550a..22117ad 100644
+--- a/auth2-pubkeyfile.c
++++ b/auth2-pubkeyfile.c
+@@ -50,6 +50,7 @@
+ #include "authfile.h"
+ #include "match.h"
+ #include "ssherr.h"
++#include "xmalloc.h"
+
+ int
+ auth_authorise_keyopts(struct passwd *pw, struct sshauthopt *opts,
+@@ -146,20 +147,23 @@ auth_authorise_keyopts(struct passwd *pw, struct sshauthopt *opts,
+ static int
+ match_principals_option(const char *principal_list, struct sshkey_cert *cert)
+ {
+-	char *result;
++	char *list, *olist, *entry;
+ 	u_int i;
+
+-	/* XXX percent_expand() sequences for authorized_principals? */
+-
+-	for (i = 0; i < cert->nprincipals; i++) {
+-		if ((result = match_list(cert->principals[i],
+-		    principal_list, NULL)) != NULL) {
+-			debug3("matched principal from key options \"%.100s\"",
+-			    result);
+-			free(result);
+-			return 1;
++	olist = list = xstrdup(principal_list);
++	for (;;) {
++		if ((entry = strsep(&list, ",")) == NULL || *entry == \0\)
++			break;
++		for (i = 0; i < cert->nprincipals; i++) {
++			if (strcmp(entry, cert->principals[i]) == 0) {
++				debug3("matched principal from key options \"%.100s\"",
++				    entry);
++				free(olist);
++				return 1;
++			}
+ 		}
+ 	}
++	free(olist);
+ 	return 0;
+ }
+
+diff --git a/sshconnect2.c b/sshconnect2.c
+index 42e6cac..ec85246 100644
+--- a/sshconnect2.c
++++ b/sshconnect2.c
+@@ -89,6 +89,7 @@ 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)
+@@ -98,6 +99,10 @@ verify_host_key_callback(struct sshkey *hostkey, struct ssh *ssh)
+ 	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.");
+@@ -1597,34 +1602,37 @@ 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,
+-- 
+2.45.4
+
@@ -47,6 +47,7 @@ Patch407:       CVE-2026-35414.patch
 # The tests fail with the following error:
 #   dlsym(sk_api_version) failed: (...)/sk-dummy.so: undefined symbol: sk_api_version
 Patch965:       openssh-8.2p1-visibility.patch
+Patch966:       CVE-2026-35387.patch
 
 BuildRequires:  audit-devel
 BuildRequires:  autoconf
@@ -108,6 +109,7 @@ The module is most useful for su and sudo service stacks.
 
 %prep
 %setup -q -a 3
+%patch 966 -p1
 
 pushd pam_ssh_agent_auth-%{pam_ssh_agent_ver}
 %patch -P 300 -p2 -b .psaa-build