upstream commit

Refuse RSA keys <1024 bits in length. Improve reporting
for keys that do not meet this requirement. ok markus@

Upstream-ID: b385e2a7b13b1484792ee681daaf79e1e203df6c

7 files changed, 54 insertions, 25 deletions

diff --git a/ssh-keygen.c b/ssh-keygen.c
index 51c24bc55..7886582d7 100644
--- a/ssh-keygen.c
+++ b/ssh-keygen.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh-keygen.c,v 1.302 2017/04/30 23:18:44 djm Exp $ */
+/* $OpenBSD: ssh-keygen.c,v 1.303 2017/05/07 23:15:59 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1994 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -226,13 +226,21 @@ type_bits_valid(int type, const char *name, u_int32_t *bitsp)
             OPENSSL_DSA_MAX_MODULUS_BITS : OPENSSL_RSA_MAX_MODULUS_BITS;
         if (*bitsp > maxbits)
                 fatal("key bits exceeds maximum %d", maxbits);
-        if (type == KEY_DSA && *bitsp != 1024)
-                fatal("DSA keys must be 1024 bits");
-        else if (type != KEY_ECDSA && type != KEY_ED25519 && *bitsp < 1024)
-                fatal("Key must at least be 1024 bits");
-        else if (type == KEY_ECDSA && sshkey_ecdsa_bits_to_nid(*bitsp) == -1)
-                fatal("Invalid ECDSA key length - valid lengths are "
-                    "256, 384 or 521 bits");
+        switch (type) {
+        case KEY_DSA:
+                if (*bitsp != 1024)
+                        fatal("Invalid DSA key length: must be 1024 bits");
+                break;
+        case KEY_RSA:
+                if (*bitsp < SSH_RSA_MINIMUM_MODULUS_SIZE)
+                        fatal("Invalid RSA key length: minimum is %d bits",
+                            SSH_RSA_MINIMUM_MODULUS_SIZE);
+                break;
+        case KEY_ECDSA:
+                if (sshkey_ecdsa_bits_to_nid(*bitsp) == -1)
+                        fatal("Invalid ECDSA key length: valid lengths are "
+                            "256, 384 or 521 bits");
+        }
 #endif
 }
 
diff --git a/ssh-rsa.c b/ssh-rsa.c
index cde05df10..e8acc01fa 100644
--- a/ssh-rsa.c
+++ b/ssh-rsa.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh-rsa.c,v 1.60 2016/09/12 23:39:34 djm Exp $ */
+/* $OpenBSD: ssh-rsa.c,v 1.61 2017/05/07 23:15:59 djm Exp $ */
 /*
  * Copyright (c) 2000, 2003 Markus Friedl <markus@openbsd.org>
  *
@@ -99,9 +99,10 @@ ssh_rsa_sign(const struct sshkey *key, u_char **sigp, size_t *lenp,
         else
                 hash_alg = rsa_hash_alg_from_ident(alg_ident);
         if (key == NULL || key->rsa == NULL || hash_alg == -1 ||
-            sshkey_type_plain(key->type) != KEY_RSA ||
-            BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE)
+            sshkey_type_plain(key->type) != KEY_RSA)
                 return SSH_ERR_INVALID_ARGUMENT;
+        if (BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE)
+                return SSH_ERR_KEY_LENGTH;
         slen = RSA_size(key->rsa);
         if (slen <= 0 || slen > SSHBUF_MAX_BIGNUM)
                 return SSH_ERR_INVALID_ARGUMENT;
@@ -172,9 +173,10 @@ ssh_rsa_verify(const struct sshkey *key,
 
         if (key == NULL || key->rsa == NULL ||
             sshkey_type_plain(key->type) != KEY_RSA ||
-            BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE ||
             sig == NULL || siglen == 0)
                 return SSH_ERR_INVALID_ARGUMENT;
+        if (BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE)
+                return SSH_ERR_KEY_LENGTH;
 
         if ((b = sshbuf_from(sig, siglen)) == NULL)
                 return SSH_ERR_ALLOC_FAIL;
diff --git a/ssh.h b/ssh.h
index 08d05ce29..12d800922 100644
--- a/ssh.h
+++ b/ssh.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh.h,v 1.86 2017/05/03 21:08:09 naddy Exp $ */
+/* $OpenBSD: ssh.h,v 1.87 2017/05/07 23:15:59 djm Exp $ */
 
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
@@ -98,8 +98,5 @@
 #define SSH_PRIVSEP_USER                "sshd"
 #endif
 
-/* Minimum modulus size (n) for RSA keys. */
-#define SSH_RSA_MINIMUM_MODULUS_SIZE    768
-
 /* Listen backlog for sshd, ssh-agent and forwarding sockets */
 #define SSH_LISTEN_BACKLOG              128
diff --git a/ssherr.c b/ssherr.c
index 680207063..4bd5f59cc 100644
--- a/ssherr.c
+++ b/ssherr.c
@@ -1,4 +1,4 @@
-/*      $OpenBSD: ssherr.c,v 1.5 2015/09/13 14:39:16 tim Exp $  */
+/*      $OpenBSD: ssherr.c,v 1.6 2017/05/07 23:15:59 djm Exp $  */
 /*
  * Copyright (c) 2011 Damien Miller
  *
@@ -135,6 +135,8 @@ ssh_err(int n)
                 return "Connection corrupted";
         case SSH_ERR_PROTOCOL_ERROR:
                 return "Protocol error";
+        case SSH_ERR_KEY_LENGTH:
+                return "Invalid key length";
         default:
                 return "unknown error";
         }
diff --git a/ssherr.h b/ssherr.h
index 6f771b4b7..a30781620 100644
--- a/ssherr.h
+++ b/ssherr.h
@@ -1,4 +1,4 @@
-/*      $OpenBSD: ssherr.h,v 1.3 2015/01/30 01:13:33 djm Exp $  */
+/*      $OpenBSD: ssherr.h,v 1.4 2017/05/07 23:15:59 djm Exp $  */
 /*
  * Copyright (c) 2011 Damien Miller
  *
@@ -77,6 +77,7 @@
 #define SSH_ERR_CONN_TIMEOUT                    -53
 #define SSH_ERR_CONN_CORRUPT                    -54
 #define SSH_ERR_PROTOCOL_ERROR                  -55
+#define SSH_ERR_KEY_LENGTH                      -56
 
 /* Translate a numeric error code to a human-readable error string */
 const char *ssh_err(int n);
diff --git a/sshkey.c b/sshkey.c
index 0f6468197..6518c6f0b 100644
--- a/sshkey.c
+++ b/sshkey.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sshkey.c,v 1.48 2017/04/30 23:18:44 djm Exp $ */
+/* $OpenBSD: sshkey.c,v 1.49 2017/05/07 23:15:59 djm Exp $ */
 /*
  * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
  * Copyright (c) 2008 Alexander von Gernler.  All rights reserved.
@@ -1392,10 +1392,11 @@ rsa_generate_private_key(u_int bits, RSA **rsap)
         BIGNUM *f4 = NULL;
         int ret = SSH_ERR_INTERNAL_ERROR;
 
-        if (rsap == NULL ||
-            bits < SSH_RSA_MINIMUM_MODULUS_SIZE ||
-            bits > SSHBUF_MAX_BIGNUM * 8)
+        if (rsap == NULL)
                 return SSH_ERR_INVALID_ARGUMENT;
+        if (bits < SSH_RSA_MINIMUM_MODULUS_SIZE ||
+            bits > SSHBUF_MAX_BIGNUM * 8)
+                return SSH_ERR_KEY_LENGTH;
         *rsap = NULL;
         if ((private = RSA_new()) == NULL || (f4 = BN_new()) == NULL) {
                 ret = SSH_ERR_ALLOC_FAIL;
@@ -1423,8 +1424,10 @@ dsa_generate_private_key(u_int bits, DSA **dsap)
         DSA *private;
         int ret = SSH_ERR_INTERNAL_ERROR;
 
-        if (dsap == NULL || bits != 1024)
+        if (dsap == NULL)
                 return SSH_ERR_INVALID_ARGUMENT;
+        if (bits != 1024)
+                return SSH_ERR_KEY_LENGTH;
         if ((private = DSA_new()) == NULL) {
                 ret = SSH_ERR_ALLOC_FAIL;
                 goto out;
@@ -1876,6 +1879,10 @@ sshkey_from_blob_internal(struct sshbuf *b, struct sshkey **keyp,
                         ret = SSH_ERR_INVALID_FORMAT;
                         goto out;
                 }
+                if (BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE) {
+                        ret = SSH_ERR_KEY_LENGTH;
+                        goto out;
+                }
 #ifdef DEBUG_PK
                 RSA_print_fp(stderr, key->rsa, 8);
 #endif
@@ -2643,6 +2650,10 @@ sshkey_private_deserialize(struct sshbuf *buf, struct sshkey **kp)
                     (r = sshbuf_get_bignum2(buf, k->rsa->q)) != 0 ||
                     (r = rsa_generate_additional_parameters(k->rsa)) != 0)
                         goto out;
+                if (BN_num_bits(k->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE) {
+                        r = SSH_ERR_KEY_LENGTH;
+                        goto out;
+                }
                 break;
         case KEY_RSA_CERT:
                 if ((r = sshkey_froms(buf, &k)) != 0 ||
@@ -2653,6 +2664,10 @@ sshkey_private_deserialize(struct sshbuf *buf, struct sshkey **kp)
                     (r = sshbuf_get_bignum2(buf, k->rsa->q)) != 0 ||
                     (r = rsa_generate_additional_parameters(k->rsa)) != 0)
                         goto out;
+                if (BN_num_bits(k->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE) {
+                        r = SSH_ERR_KEY_LENGTH;
+                        goto out;
+                }
                 break;
 #endif /* WITH_OPENSSL */
         case KEY_ED25519:
@@ -3427,6 +3442,10 @@ sshkey_parse_private_pem_fileblob(struct sshbuf *blob, int type,
                         r = SSH_ERR_LIBCRYPTO_ERROR;
                         goto out;
                 }
+                if (BN_num_bits(prv->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE) {
+                        r = SSH_ERR_KEY_LENGTH;
+                        goto out;
+                }
         } else if (pk->type == EVP_PKEY_DSA &&
             (type == KEY_UNSPEC || type == KEY_DSA)) {
                 if ((prv = sshkey_new(KEY_UNSPEC)) == NULL) {
diff --git a/sshkey.h b/sshkey.h
index fc1956605..b0b5b2749 100644
--- a/sshkey.h
+++ b/sshkey.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: sshkey.h,v 1.17 2017/05/03 21:08:09 naddy Exp $ */
+/* $OpenBSD: sshkey.h,v 1.18 2017/05/07 23:15:59 djm Exp $ */
 
 /*
  * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
@@ -46,7 +46,7 @@
 # define EC_POINT       void
 #endif /* WITH_OPENSSL */
 
-#define SSH_RSA_MINIMUM_MODULUS_SIZE    768
+#define SSH_RSA_MINIMUM_MODULUS_SIZE    1024
 #define SSH_KEY_MAX_SIGN_DATA_SIZE      (1 << 20)
 
 struct sshbuf;