X-Git-Url: https://git.distorted.org.uk/u/mdw/putty/blobdiff_plain/0405e71f25335f47635d29b5a9d9b815191e6586..70cd2027d47923b19665b4b1e31f462ec63f8c57:/ssh.c

diff --git a/ssh.c b/ssh.c
index 0edaf932..19c93df4 100644
--- a/ssh.c
+++ b/ssh.c
@@ -182,6 +182,7 @@ static const char *const ssh2_disconnect_reasons[] = {
 #define BUG_NEEDS_SSH1_PLAIN_PASSWORD        	  4
 #define BUG_CHOKES_ON_RSA	        	  8
 #define BUG_SSH2_RSA_PADDING	        	 16
+#define BUG_SSH2_DERIVEKEY                       32
 
 static int ssh_pkt_ctx = 0;
 
@@ -885,6 +886,15 @@ static int ssh2_rdpkt(unsigned char **data, int *datalen)
     st->pad = pktin.data[4];
 
     /*
+     * _Completely_ silly lengths should be stomped on before they
+     * do us any more damage.
+     */
+    if (st->len < 0 || st->pad < 0 || st->len + st->pad < 0) {
+	bombout(("Incoming packet was garbled on decryption"));
+	crReturn(0);
+    }
+
+    /*
      * This enables us to deduce the payload length.
      */
     st->payload = st->len - st->pad - 1;
@@ -1692,6 +1702,16 @@ static void ssh_detect_bugs(char *vstring)
 	logevent("We believe remote version has SSH2 HMAC bug");
     }
 
+    if (!strncmp(imp, "2.0.", 4)) {
+	/*
+	 * These versions have the key-derivation bug (failing to
+	 * include the literal shared secret in the hashes that
+	 * generate the keys).
+	 */
+	ssh_remote_bugs |= BUG_SSH2_DERIVEKEY;
+	logevent("We believe remote version has SSH2 key-derivation bug");
+    }
+
     if ((!strncmp(imp, "OpenSSH_2.", 10) && imp[10]>='5' && imp[10]<='9') ||
 	(!strncmp(imp, "OpenSSH_3.", 10) && imp[10]>='0' && imp[10]<='2')) {
 	/*
@@ -3488,14 +3508,16 @@ static void ssh2_mkkey(Bignum K, char *H, char *sessid, char chr,
     SHA_State s;
     /* First 20 bytes. */
     SHA_Init(&s);
-    sha_mpint(&s, K);
+    if (!(ssh_remote_bugs & BUG_SSH2_DERIVEKEY))
+	sha_mpint(&s, K);
     SHA_Bytes(&s, H, 20);
     SHA_Bytes(&s, &chr, 1);
     SHA_Bytes(&s, sessid, 20);
     SHA_Final(&s, keyspace);
     /* Next 20 bytes. */
     SHA_Init(&s);
-    sha_mpint(&s, K);
+    if (!(ssh_remote_bugs & BUG_SSH2_DERIVEKEY))
+	sha_mpint(&s, K);
     SHA_Bytes(&s, H, 20);
     SHA_Bytes(&s, keyspace, 20);
     SHA_Final(&s, keyspace + 20);