add a helper function to match a key type to a list of signature

algorithms. RSA keys can make signatures with multiple algorithms,
so some special handling is required.
ok markus@

diff --git a/usr.bin/ssh/sshkey.c b/usr.bin/ssh/sshkey.c
index 193f6ec..cdc29e5 100644 (file)
--- a/usr.bin/ssh/sshkey.c
+++ b/usr.bin/ssh/sshkey.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sshkey.c,v 1.119 2021/07/23 03:37:52 djm Exp $ */
+/* $OpenBSD: sshkey.c,v 1.120 2022/01/06 22:05:42 djm Exp $ */
 /*
  * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
  * Copyright (c) 2008 Alexander von Gernler.  All rights reserved.
@@ -234,6 +234,29 @@ sshkey_ecdsa_nid_from_name(const char *name)
        return -1;
 }
 
+int
+sshkey_match_keyname_to_sigalgs(const char *keyname, const char *sigalgs)
+{
+       int ktype;
+
+       if (sigalgs == NULL || *sigalgs == '\0' ||
+           (ktype = sshkey_type_from_name(keyname)) == KEY_UNSPEC)
+               return 0;
+       else if (ktype == KEY_RSA) {
+               return match_pattern_list("ssh-rsa", sigalgs, 0) == 1 ||
+                   match_pattern_list("rsa-sha2-256", sigalgs, 0) == 1 ||
+                   match_pattern_list("rsa-sha2-512", sigalgs, 0) == 1;
+       } else if (ktype == KEY_RSA_CERT) {
+               return match_pattern_list("ssh-rsa-cert-v01@openssh.com",
+                   sigalgs, 0) == 1 ||
+                   match_pattern_list("rsa-sha2-256-cert-v01@openssh.com",
+                   sigalgs, 0) == 1 ||
+                   match_pattern_list("rsa-sha2-512-cert-v01@openssh.com",
+                   sigalgs, 0) == 1;
+       } else
+               return match_pattern_list(keyname, sigalgs, 0) == 1;
+}
+
 char *
 sshkey_alg_list(int certs_only, int plain_only, int include_sigonly, char sep)
 {

diff --git a/usr.bin/ssh/sshkey.h b/usr.bin/ssh/sshkey.h
index ecae86e..125cadb 100644 (file)
--- a/usr.bin/ssh/sshkey.h
+++ b/usr.bin/ssh/sshkey.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: sshkey.h,v 1.50 2021/07/23 03:37:52 djm Exp $ */
+/* $OpenBSD: sshkey.h,v 1.51 2022/01/06 22:05:42 djm Exp $ */
 
 /*
  * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
@@ -186,6 +186,10 @@ int         sshkey_is_cert(const struct sshkey *);
 int     sshkey_is_sk(const struct sshkey *);
 int     sshkey_type_is_cert(int);
 int     sshkey_type_plain(int);
+
+/* Returns non-zero if key name match sigalgs pattern list. (handles RSA) */
+int     sshkey_match_keyname_to_sigalgs(const char *, const char *);
+
 int     sshkey_to_certified(struct sshkey *);
 int     sshkey_drop_cert(struct sshkey *);
 int     sshkey_cert_copy(const struct sshkey *, struct sshkey *);