Fix key type checks with RSA-SHA2 signature types

5 files changed, 133 insertions, 7 deletions

diff --git a/debian/.git-dpm b/debian/.git-dpm
index 8a18e26dc..a45865db0 100644
--- a/debian/.git-dpm
+++ b/debian/.git-dpm
@@ -1,6 +1,6 @@
 # see git-dpm(1) from git-dpm package
-125924e47db3713a85a70e0f8d6c23818d2ea054
-125924e47db3713a85a70e0f8d6c23818d2ea054
+5e021158aa22cc64da4fca1618ee0bfd2d031049
+5e021158aa22cc64da4fca1618ee0bfd2d031049
 3d246f10429fc9a37b98eabef94fe8dc7c61002b
 3d246f10429fc9a37b98eabef94fe8dc7c61002b
 openssh_7.9p1.orig.tar.gz
diff --git a/debian/changelog b/debian/changelog
index 61189919c..ce7ec26fe 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -1,3 +1,11 @@
+openssh (1:7.9p1-8) UNRELEASED; urgency=medium
+
+  * Apply upstream patch to fix bug in HostbasedAcceptedKeyTypes and
+    PubkeyAcceptedKeyTypes options in the case where only RSA-SHA2 signature
+    types were specified.
+
+ -- Colin Watson <cjwatson@debian.org>  Thu, 28 Feb 2019 10:33:32 +0000
+
 openssh (1:7.9p1-7) unstable; urgency=medium
 
   * Recommend "default-logind | logind | libpam-systemd" rather than just
diff --git a/debian/patches/fix-key-type-check.patch b/debian/patches/fix-key-type-check.patch
new file mode 100644
index 000000000..846df5768
--- /dev/null
+++ b/debian/patches/fix-key-type-check.patch
@@ -0,0 +1,88 @@
+From 5e021158aa22cc64da4fca1618ee0bfd2d031049 Mon Sep 17 00:00:00 2001
+From: "djm@openbsd.org" <djm@openbsd.org>
+Date: Fri, 16 Nov 2018 02:43:56 +0000
+Subject: upstream: fix bug in HostbasedAcceptedKeyTypes and
+
+PubkeyAcceptedKeyTypes options. If only RSA-SHA2 siganture types were
+specified, then authentication would always fail for RSA keys as the monitor
+checks only the base key (not the signature algorithm) type against
+*AcceptedKeyTypes. bz#2746; reported by Jakub Jelen; ok dtucker
+
+OpenBSD-Commit-ID: 117bc3dc54578dbdb515a1d3732988cb5b00461b
+
+Origin: upstream, https://anongit.mindrot.org/openssh.git/commit/?id=cd9467318b56e6e93ff9575c906ff8350af9b8a2
+Last-Update: 2019-02-28
+
+Patch-Name: fix-key-type-check.patch
+---
+ monitor.c | 39 ++++++++++++++++++++++++++++++++++-----
+ 1 file changed, 34 insertions(+), 5 deletions(-)
+
+diff --git a/monitor.c b/monitor.c
+index 08fddabd7..037d6d333 100644
+--- a/monitor.c
++++ b/monitor.c
+@@ -1,4 +1,4 @@
+-/* $OpenBSD: monitor.c,v 1.186 2018/07/20 03:46:34 djm Exp $ */
++/* $OpenBSD: monitor.c,v 1.188 2018/11/16 02:43:56 djm Exp $ */
+ /*
+  * Copyright 2002 Niels Provos <provos@citi.umich.edu>
+  * Copyright 2002 Markus Friedl <markus@openbsd.org>
+@@ -892,6 +892,35 @@ mm_answer_authrole(int sock, struct sshbuf *m)
+        return (0);
+ }
+ 
++/*
++ * Check that the key type appears in the supplied pattern list, ignoring
++ * mismatches in the signature algorithm. (Signature algorithm checks are
++ * performed in the unprivileged authentication code).
++ * Returns 1 on success, 0 otherwise.
++ */
++static int
++key_base_type_match(const char *method, const struct sshkey *key,
++    const char *list)
++{
++       char *s, *l, *ol = xstrdup(list);
++       int found = 0;
++
++       l = ol;
++       for ((s = strsep(&l, ",")); s && *s != '\0'; (s = strsep(&l, ","))) {
++               if (sshkey_type_from_name(s) == key->type) {
++                       found = 1;
++                       break;
++               }
++       }
++       if (!found) {
++               error("%s key type %s is not in permitted list %s", method,
++                   sshkey_ssh_name(key), list);
++       }
++
++       free(ol);
++       return found;
++}
++
+ int
+ mm_answer_authpassword(int sock, struct sshbuf *m)
+ {
+@@ -1197,8 +1226,8 @@ mm_answer_keyallowed(int sock, struct sshbuf *m)
+                                break;
+                        if (auth2_key_already_used(authctxt, key))
+                                break;
+-                       if (match_pattern_list(sshkey_ssh_name(key),
+-                           options.pubkey_key_types, 0) != 1)
++                       if (!key_base_type_match(auth_method, key,
++                           options.pubkey_key_types))
+                                break;
+                        allowed = user_key_allowed(ssh, authctxt->pw, key,
+                            pubkey_auth_attempt, &opts);
+@@ -1209,8 +1238,8 @@ mm_answer_keyallowed(int sock, struct sshbuf *m)
+                                break;
+                        if (auth2_key_already_used(authctxt, key))
+                                break;
+-                       if (match_pattern_list(sshkey_ssh_name(key),
+-                           options.hostbased_key_types, 0) != 1)
++                       if (!key_base_type_match(auth_method, key,
++                           options.hostbased_key_types))
+                                break;
+                        allowed = hostbased_key_allowed(authctxt->pw,
+                            cuser, chost, key);
diff --git a/debian/patches/series b/debian/patches/series
index 4403cba3b..12358dcf0 100644
--- a/debian/patches/series
+++ b/debian/patches/series
@@ -28,3 +28,4 @@ scp-disallow-dot-or-empty-filename.patch
 sanitize-scp-filenames-via-snmprintf.patch
 have-progressmeter-force-update-at-beginning-and-end-transfer.patch
 check-filenames-in-scp-client.patch
+fix-key-type-check.patch
diff --git a/monitor.c b/monitor.c
index 08fddabd7..037d6d333 100644
--- a/monitor.c
+++ b/monitor.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: monitor.c,v 1.186 2018/07/20 03:46:34 djm Exp $ */
+/* $OpenBSD: monitor.c,v 1.188 2018/11/16 02:43:56 djm Exp $ */
 /*
  * Copyright 2002 Niels Provos <provos@citi.umich.edu>
  * Copyright 2002 Markus Friedl <markus@openbsd.org>
@@ -892,6 +892,35 @@ mm_answer_authrole(int sock, struct sshbuf *m)
         return (0);
 }
 
+/*
+ * Check that the key type appears in the supplied pattern list, ignoring
+ * mismatches in the signature algorithm. (Signature algorithm checks are
+ * performed in the unprivileged authentication code).
+ * Returns 1 on success, 0 otherwise.
+ */
+static int
+key_base_type_match(const char *method, const struct sshkey *key,
+    const char *list)
+{
+        char *s, *l, *ol = xstrdup(list);
+        int found = 0;
+
+        l = ol;
+        for ((s = strsep(&l, ",")); s && *s != '\0'; (s = strsep(&l, ","))) {
+                if (sshkey_type_from_name(s) == key->type) {
+                        found = 1;
+                        break;
+                }
+        }
+        if (!found) {
+                error("%s key type %s is not in permitted list %s", method,
+                    sshkey_ssh_name(key), list);
+        }
+
+        free(ol);
+        return found;
+}
+
 int
 mm_answer_authpassword(int sock, struct sshbuf *m)
 {
@@ -1197,8 +1226,8 @@ mm_answer_keyallowed(int sock, struct sshbuf *m)
                                 break;
                         if (auth2_key_already_used(authctxt, key))
                                 break;
-                        if (match_pattern_list(sshkey_ssh_name(key),
-                            options.pubkey_key_types, 0) != 1)
+                        if (!key_base_type_match(auth_method, key,
+                            options.pubkey_key_types))
                                 break;
                         allowed = user_key_allowed(ssh, authctxt->pw, key,
                             pubkey_auth_attempt, &opts);
@@ -1209,8 +1238,8 @@ mm_answer_keyallowed(int sock, struct sshbuf *m)
                                 break;
                         if (auth2_key_already_used(authctxt, key))
                                 break;
-                        if (match_pattern_list(sshkey_ssh_name(key),
-                            options.hostbased_key_types, 0) != 1)
+                        if (!key_base_type_match(auth_method, key,
+                            options.hostbased_key_types))
                                 break;
                         allowed = hostbased_key_allowed(authctxt->pw,
                             cuser, chost, key);