1 files changed, 67 insertions, 15 deletions

diff --git a/auth2-pubkey.c b/auth2-pubkey.c
index f78b046b8..0bda5c9dd 100644
--- a/auth2-pubkey.c
+++ b/auth2-pubkey.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: auth2-pubkey.c,v 1.41 2014/07/15 15:54:14 millert Exp $ */
+/* $OpenBSD: auth2-pubkey.c,v 1.47 2015/02/17 00:14:05 djm Exp $ */
 /*
  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
  *
@@ -41,6 +41,7 @@
 #include <string.h>
 #include <time.h>
 #include <unistd.h>
+#include <limits.h>
 
 #include "xmalloc.h"
 #include "ssh.h"
@@ -122,6 +123,17 @@ userauth_pubkey(Authctxt *authctxt)
                     "signature scheme");
                 goto done;
         }
+        if (auth2_userkey_already_used(authctxt, key)) {
+                logit("refusing previously-used %s key", key_type(key));
+                goto done;
+        }
+        if (match_pattern_list(sshkey_ssh_name(key), options.pubkey_key_types,
+            strlen(options.pubkey_key_types), 0) != 1) {
+                logit("%s: key type %s not in PubkeyAcceptedKeyTypes",
+                    __func__, sshkey_ssh_name(key));
+                goto done;
+        }
+
         if (have_sig) {
                 sig = packet_get_string(&slen);
                 packet_check_eom();
@@ -159,8 +171,12 @@ userauth_pubkey(Authctxt *authctxt)
                 authenticated = 0;
                 if (PRIVSEP(user_key_allowed(authctxt->pw, key)) &&
                     PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b),
-                    buffer_len(&b))) == 1)
+                    buffer_len(&b))) == 1) {
                         authenticated = 1;
+                        /* Record the successful key to prevent reuse */
+                        auth2_record_userkey(authctxt, key);
+                        key = NULL; /* Don't free below */
+                }
                 buffer_free(&b);
                 free(sig);
         } else {
@@ -212,17 +228,20 @@ pubkey_auth_info(Authctxt *authctxt, const Key *key, const char *fmt, ...)
         }
 
         if (key_is_cert(key)) {
-                fp = key_fingerprint(key->cert->signature_key,
-                    SSH_FP_MD5, SSH_FP_HEX);
+                fp = sshkey_fingerprint(key->cert->signature_key,
+                    options.fingerprint_hash, SSH_FP_DEFAULT);
                 auth_info(authctxt, "%s ID %s (serial %llu) CA %s %s%s%s", 
                     key_type(key), key->cert->key_id,
                     (unsigned long long)key->cert->serial,
-                    key_type(key->cert->signature_key), fp,
+                    key_type(key->cert->signature_key),
+                    fp == NULL ? "(null)" : fp,
                     extra == NULL ? "" : ", ", extra == NULL ? "" : extra);
                 free(fp);
         } else {
-                fp = key_fingerprint(key, SSH_FP_MD5, SSH_FP_HEX);
-                auth_info(authctxt, "%s %s%s%s", key_type(key), fp,
+                fp = sshkey_fingerprint(key, options.fingerprint_hash,
+                    SSH_FP_DEFAULT);
+                auth_info(authctxt, "%s %s%s%s", key_type(key),
+                    fp == NULL ? "(null)" : fp,
                     extra == NULL ? "" : ", ", extra == NULL ? "" : extra);
                 free(fp);
         }
@@ -367,8 +386,9 @@ check_authkeys_file(FILE *f, char *file, Key* key, struct passwd *pw)
                                 continue;
                         if (!key_is_cert_authority)
                                 continue;
-                        fp = key_fingerprint(found, SSH_FP_MD5,
-                            SSH_FP_HEX);
+                        if ((fp = sshkey_fingerprint(found,
+                            options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
+                                continue;
                         debug("matching CA found: file %s, line %lu, %s %s",
                             file, linenum, key_type(found), fp);
                         /*
@@ -407,11 +427,13 @@ check_authkeys_file(FILE *f, char *file, Key* key, struct passwd *pw)
                                 continue;
                         if (key_is_cert_authority)
                                 continue;
-                        found_key = 1;
-                        fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX);
+                        if ((fp = sshkey_fingerprint(found,
+                            options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
+                                continue;
                         debug("matching key found: file %s, line %lu %s %s",
                             file, linenum, key_type(found), fp);
                         free(fp);
+                        found_key = 1;
                         break;
                 }
         }
@@ -433,11 +455,12 @@ user_cert_trusted_ca(struct passwd *pw, Key *key)
         if (!key_is_cert(key) || options.trusted_user_ca_keys == NULL)
                 return 0;
 
-        ca_fp = key_fingerprint(key->cert->signature_key,
-            SSH_FP_MD5, SSH_FP_HEX);
+        if ((ca_fp = sshkey_fingerprint(key->cert->signature_key,
+            options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
+                return 0;
 
-        if (key_in_file(key->cert->signature_key,
-            options.trusted_user_ca_keys, 1) != 1) {
+        if (sshkey_in_file(key->cert->signature_key,
+            options.trusted_user_ca_keys, 1, 0) != 0) {
                 debug2("%s: CA %s %s is not listed in %s", __func__,
                     key_type(key->cert->signature_key), ca_fp,
                     options.trusted_user_ca_keys);
@@ -683,6 +706,35 @@ user_key_allowed(struct passwd *pw, Key *key)
         return success;
 }
 
+/* Records a public key in the list of previously-successful keys */
+void
+auth2_record_userkey(Authctxt *authctxt, struct sshkey *key)
+{
+        struct sshkey **tmp;
+
+        if (authctxt->nprev_userkeys >= INT_MAX ||
+            (tmp = reallocarray(authctxt->prev_userkeys,
+            authctxt->nprev_userkeys + 1, sizeof(*tmp))) == NULL)
+                fatal("%s: reallocarray failed", __func__);
+        authctxt->prev_userkeys = tmp;
+        authctxt->prev_userkeys[authctxt->nprev_userkeys] = key;
+        authctxt->nprev_userkeys++;
+}
+
+/* Checks whether a key has already been used successfully for authentication */
+int
+auth2_userkey_already_used(Authctxt *authctxt, struct sshkey *key)
+{
+        u_int i;
+
+        for (i = 0; i < authctxt->nprev_userkeys; i++) {
+                if (sshkey_equal_public(key, authctxt->prev_userkeys[i])) {
+                        return 1;
+                }
+        }
+        return 0;
+}
+
 Authmethod method_pubkey = {
         "publickey",
         userauth_pubkey,