[openssh-commits] [openssh] 05/12: upstream: correctly match ECDSA signature algorithms against
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djm pushed a commit to branch V_10_3
in repository openssh.
commit fd1c7e131f331942d20f42f31e79912d570081fa
Author: djm at openbsd.org <djm at openbsd.org>
AuthorDate: Thu Apr 2 07:48:13 2026 +0000
upstream: correctly match ECDSA signature algorithms against
algorithm allowlists: HostKeyAlgorithms, PubkeyAcceptedAlgorithms and
HostbasedAcceptedAlgorithms.
Previously, if any ECDSA type (say "ecdsa-sha2-nistp521") was
present in one of these lists, then all ECDSA algorithms would
be permitted.
Reported by Christos Papakonstantinou of Cantina and Spearbit.
OpenBSD-Commit-ID: c790e2687c35989ae34a00e709be935c55b16a86
---
auth2-hostbased.c | 9 +++++----
auth2-pubkey.c | 9 +++++----
auth2-pubkeyfile.c | 26 +++++++++++++++-----------
sshconnect2.c | 28 ++++++++++++++++++----------
4 files changed, 43 insertions(+), 29 deletions(-)
diff --git a/auth2-hostbased.c b/auth2-hostbased.c
index e2ed8b3eb..8a1acdec3 100644
--- a/auth2-hostbased.c
+++ b/auth2-hostbased.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: auth2-hostbased.c,v 1.56 2025/12/22 01:49:03 djm Exp $ */
+/* $OpenBSD: auth2-hostbased.c,v 1.57 2026/04/02 07:48:13 djm Exp $ */
/*
* Copyright (c) 2000 Markus Friedl. All rights reserved.
*
@@ -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 be378f266..e446ef412 100644
--- a/auth2-pubkey.c
+++ b/auth2-pubkey.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: auth2-pubkey.c,v 1.125 2025/12/22 01:49:03 djm Exp $ */
+/* $OpenBSD: auth2-pubkey.c,v 1.126 2026/04/02 07:48:13 djm Exp $ */
/*
* Copyright (c) 2000 Markus Friedl. All rights reserved.
* Copyright (c) 2010 Damien Miller. All rights reserved.
@@ -148,9 +148,10 @@ 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 896ea1996..e729cc50a 100644
--- a/auth2-pubkeyfile.c
+++ b/auth2-pubkeyfile.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: auth2-pubkeyfile.c,v 1.7 2025/12/22 01:49:03 djm Exp $ */
+/* $OpenBSD: auth2-pubkeyfile.c,v 1.8 2026/04/02 07:48:13 djm Exp $ */
/*
* Copyright (c) 2000 Markus Friedl. All rights reserved.
* Copyright (c) 2010 Damien Miller. All rights reserved.
@@ -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 i"
+ "options \"%.100s\"", entry);
+ free(olist);
+ return 1;
+ }
}
}
+ free(olist);
return 0;
}
diff --git a/sshconnect2.c b/sshconnect2.c
index e4f5bd0fd..478a9a52f 100644
--- a/sshconnect2.c
+++ b/sshconnect2.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sshconnect2.c,v 1.384 2026/03/03 09:57:25 dtucker Exp $ */
+/* $OpenBSD: sshconnect2.c,v 1.385 2026/04/02 07:48:13 djm Exp $ */
/*
* Copyright (c) 2000 Markus Friedl. All rights reserved.
* Copyright (c) 2008 Damien Miller. All rights reserved.
@@ -85,6 +85,7 @@ 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)
@@ -94,6 +95,10 @@ 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.");
@@ -1598,34 +1603,37 @@ 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 at openssh.com",
- options.pubkey_accepted_algos, 0) == 1)
+ allowlist, 0) == 1)
return 1;
if (match_pattern_list("rsa-sha2-256-cert-v01 at 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,
--
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