Merge pull request #7 from tigeli/master

fix security issues

openssh/auth-options.c

@@ -172,7 +172,7 @@ auth_parse_options(struct passwd *pw, char *opts, char *file, u_long linenum)
 				goto bad_option;
 			}
 			forced_command[i] = '\0';
-			auth_debug_add("Forced command: %.900s", forced_command);
+			auth_debug_add("Forced command.");
 			opts++;
 			goto next_option;
 		}

openssh/bufaux.c

@@ -202,6 +202,39 @@ buffer_get_string(Buffer *buffer, u_int *length_ptr)
 	return (ret);
 }
 
+char *
+buffer_get_cstring_ret(Buffer *buffer, u_int *length_ptr)
+{
+	u_int length;
+	char *cp, *ret = buffer_get_string_ret(buffer, &length);
+
+	if (ret == NULL)
+		return NULL;
+	if ((cp = memchr(ret, '\0', length)) != NULL) {
+		/* XXX allow \0 at end-of-string for a while, remove later */
+		if (cp == ret + length - 1)
+			error("buffer_get_cstring_ret: string contains \\0");
+		else {
+			bzero(ret, length);
+			xfree(ret);
+			return NULL;
+		}
+	}
+	if (length_ptr != NULL)
+		*length_ptr = length;
+	return ret;
+}
+
+char *
+buffer_get_cstring(Buffer *buffer, u_int *length_ptr)
+{
+	char *ret;
+
+	if ((ret = buffer_get_cstring_ret(buffer, length_ptr)) == NULL)
+		fatal("buffer_get_cstring: buffer error");
+	return ret;
+}
+
 void *
 buffer_get_string_ptr_ret(Buffer *buffer, u_int *length_ptr)
 {

openssh/buffer.h

@@ -68,6 +68,7 @@ void    buffer_put_char(Buffer *, int);
 void   *buffer_get_string(Buffer *, u_int *);
 void   *buffer_get_string_ptr(Buffer *, u_int *);
 void    buffer_put_string(Buffer *, const void *, u_int);
+char   *buffer_get_cstring(Buffer *, u_int *);
 void	buffer_put_cstring(Buffer *, const char *);
 
 #define buffer_skip_string(b) \
@@ -81,6 +82,7 @@ int	buffer_get_short_ret(u_short *, Buffer *);
 int	buffer_get_int_ret(u_int *, Buffer *);
 int	buffer_get_int64_ret(u_int64_t *, Buffer *);
 void	*buffer_get_string_ret(Buffer *, u_int *);
+char	*buffer_get_cstring_ret(Buffer *, u_int *);
 void	*buffer_get_string_ptr_ret(Buffer *, u_int *);
 int	buffer_get_char_ret(char *, Buffer *);
 

openssh/gss-serv.c

@@ -229,6 +229,8 @@ ssh_gssapi_parse_ename(Gssctxt *ctx, gss_buffer_t ename, gss_buffer_t name)
 	name->length = get_u32(tok+offset);
 	offset += 4;
 
+	if (UINT_MAX - offset < name->length)
+		return GSS_S_FAILURE;
 	if (ename->length < offset+name->length)
 		return GSS_S_FAILURE;
 

openssh/key.c

@@ -1515,8 +1515,8 @@ key_certify(Key *k, Key *ca)
 	buffer_put_cstring(&k->cert->certblob, key_ssh_name(k));
 
 	/* -v01 certs put nonce first */
+	arc4random_buf(&nonce, sizeof(nonce));
 	if (k->type == KEY_DSA_CERT || k->type == KEY_RSA_CERT) {
-		arc4random_buf(&nonce, sizeof(nonce));
 		buffer_put_string(&k->cert->certblob, nonce, sizeof(nonce));
 	}
 

openssh/packet.c

@@ -1546,6 +1546,13 @@ packet_get_string_ptr(u_int *length_ptr)
 	return buffer_get_string_ptr(&active_state->incoming_packet, length_ptr);
 }
 
+/* Ensures the returned string has no embedded \0 characters in it. */
+char *
+packet_get_cstring(u_int *length_ptr)
+{
+	return buffer_get_cstring(&active_state->incoming_packet, length_ptr);
+}
+
 /*
  * Sends a diagnostic message from the server to the client.  This message
  * can be sent at any time (but not while constructing another message). The

openssh/packet.h

@@ -61,6 +61,7 @@ void     packet_get_bignum(BIGNUM * value);
 void     packet_get_bignum2(BIGNUM * value);
 void	*packet_get_raw(u_int *length_ptr);
 void	*packet_get_string(u_int *length_ptr);
+char	*packet_get_cstring(u_int *length_ptr);
 void	*packet_get_string_ptr(u_int *length_ptr);
 void     packet_disconnect(const char *fmt,...) __attribute__((format(printf, 1, 2)));
 void     packet_send_debug(const char *fmt,...) __attribute__((format(printf, 1, 2)));

openssh/servconf.c

@@ -242,11 +242,11 @@ fill_default_server_options(ServerOptions *options)
 	if (options->gateway_ports == -1)
 		options->gateway_ports = 0;
 	if (options->max_startups == -1)
-		options->max_startups = 10;
+		options->max_startups = 100;
 	if (options->max_startups_rate == -1)
-		options->max_startups_rate = 100;		/* 100% */
+		options->max_startups_rate = 30;		/* 30% */
 	if (options->max_startups_begin == -1)
-		options->max_startups_begin = options->max_startups;
+		options->max_startups_begin = 10;
 	if (options->max_authtries == -1)
 		options->max_authtries = DEFAULT_AUTH_FAIL_MAX;
 	if (options->max_sessions == -1)

openssh/session.c

@@ -946,6 +946,11 @@ child_set_env(char ***envp, u_int *envsizep, const char *name,
 	u_int envsize;
 	u_int i, namelen;
 
+	if (strchr(name, '=') != NULL) {
+		error("Invalid environment variable \"%.100s\"", name);
+		return;
+	}
+
 	/*
 	 * If we're passed an uninitialized list, allocate a single null
 	 * entry before continuing.
@@ -2234,8 +2239,8 @@ session_env_req(Session *s)
 	char *name, *val;
 	u_int name_len, val_len, i;
 
-	name = packet_get_string(&name_len);
-	val = packet_get_string(&val_len);
+	name = packet_get_cstring(&name_len);
+	val = packet_get_cstring(&val_len);
 	packet_check_eom();
 
 	/* Don't set too many environment variables */

openssh/sshconnect.c

@@ -1052,26 +1052,35 @@ verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key)
 {
 	struct stat st;
 	int flags = 0;
+	Key *plain = NULL;
 
-	/* XXX certs are not yet supported for DNS */
-	if (!key_is_cert(host_key) && options.verify_host_key_dns &&
-	    verify_host_key_dns(host, hostaddr, host_key, &flags) == 0) {
-
-		if (flags & DNS_VERIFY_FOUND) {
-
-			if (options.verify_host_key_dns == 1 &&
-			    flags & DNS_VERIFY_MATCH &&
-			    flags & DNS_VERIFY_SECURE)
-				return 0;
-
-			if (flags & DNS_VERIFY_MATCH) {
-				matching_host_key_dns = 1;
-			} else {
-				warn_changed_key(host_key);
-				error("Update the SSHFP RR in DNS with the new "
-				    "host key to get rid of this message.");
+	if (options.verify_host_key_dns) {
+		/*
+		 * XXX certs are not yet supported for DNS, so downgrade
+		 * them and try the plain key.
+		 */
+		plain = key_from_private(host_key);
+		if (key_is_cert(plain))
+			key_drop_cert(plain);
+		if (verify_host_key_dns(host, hostaddr, plain, &flags) == 0) {
+			if (flags & DNS_VERIFY_FOUND) {
+				if (options.verify_host_key_dns == 1 &&
+				    flags & DNS_VERIFY_MATCH &&
+				    flags & DNS_VERIFY_SECURE) {
+					key_free(plain);
+					return 0;
+				}
+				if (flags & DNS_VERIFY_MATCH) {
+					matching_host_key_dns = 1;
+				} else {
+					warn_changed_key(plain);
+					error("Update the SSHFP RR in DNS "
+					    "with the new host key to get rid "
+					    "of this message.");
+				}
 			}
 		}
+		key_free(plain);
 	}
 
 	/* return ok if the key can be found in an old keyfile */

openssh/sshd_config

@@ -117,7 +117,7 @@ X11Forwarding yes
 #ShowPatchLevel no
 #UseDNS yes
 #PidFile /var/run/sshd.pid
-#MaxStartups 10
+#MaxStartups 10:30:100
 #PermitTunnel no
 #ChrootDirectory none
 

openssh/sshd_config.5

@@ -701,7 +701,7 @@ SSH daemon.
 Additional connections will be dropped until authentication succeeds or the
 .Cm LoginGraceTime
 expires for a connection.
-The default is 10.
+The default is 10:30:100.
 .Pp
 Alternatively, random early drop can be enabled by specifying
 the three colon separated values