2 files changed, 54 insertions, 9 deletions

diff --git a/src/lib/libssl/ssl_tlsext.c b/src/lib/libssl/ssl_tlsext.c
index d8143ce1be..3da8ebc46c 100644
--- a/src/lib/libssl/ssl_tlsext.c
+++ b/src/lib/libssl/ssl_tlsext.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssl_tlsext.c,v 1.100 2021/10/25 10:01:46 jsing Exp $ */
+/* $OpenBSD: ssl_tlsext.c,v 1.101 2021/11/01 16:37:17 jsing Exp $ */
 /*
  * Copyright (c) 2016, 2017, 2019 Joel Sing <jsing@openbsd.org>
  * Copyright (c) 2017 Doug Hogan <doug@openbsd.org>
@@ -17,6 +17,11 @@
  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */
 
+#include <sys/socket.h>
+
+#include <arpa/inet.h>
+#include <netinet/in.h>
+
 #include <ctype.h>
 
 #include <openssl/ocsp.h>
@@ -673,6 +678,29 @@ tlsext_sni_client_build(SSL *s, uint16_t msg_type, CBB *cbb)
         return 1;
 }
 
+static int
+tlsext_sni_is_ip_literal(CBS *cbs, int *is_ip)
+{
+        union {
+                struct in_addr ip4;
+                struct in6_addr ip6;
+        } addrbuf;
+        char *hostname = NULL;
+
+        *is_ip = 0;
+
+        if (!CBS_strdup(cbs, &hostname))
+                return 0;
+
+        if (inet_pton(AF_INET, hostname, &addrbuf) == 1 ||
+            inet_pton(AF_INET6, hostname, &addrbuf) == 1)
+                *is_ip = 1;
+
+        free(hostname);
+
+        return 1;
+}
+
 /*
  * Validate that the CBS contains only a hostname consisting of RFC 5890
  * compliant A-labels (see RFC 6066 section 3). Not a complete check
@@ -680,7 +708,7 @@ tlsext_sni_client_build(SSL *s, uint16_t msg_type, CBB *cbb)
  * correct structure and character set.
  */
 int
-tlsext_sni_is_valid_hostname(CBS *cbs)
+tlsext_sni_is_valid_hostname(CBS *cbs, int *is_ip)
 {
         uint8_t prev, c = 0;
         int component = 0;
@@ -691,7 +719,13 @@ tlsext_sni_is_valid_hostname(CBS *cbs)
         if (CBS_len(&hostname) > TLSEXT_MAXLEN_host_name)
                 return 0;
 
-        while(CBS_len(&hostname) > 0) {
+        /* An IP literal is invalid as a host name (RFC 6066 section 3). */
+        if (!tlsext_sni_is_ip_literal(&hostname, is_ip))
+                return 0;
+        if (*is_ip)
+                return 0;
+
+        while (CBS_len(&hostname) > 0) {
                 prev = c;
                 if (!CBS_get_u8(&hostname, &c))
                         return 0;
@@ -727,12 +761,14 @@ tlsext_sni_server_parse(SSL *s, uint16_t msg_type, CBS *cbs, int *alert)
 {
         CBS server_name_list, host_name;
         uint8_t name_type;
+        int is_ip;
 
         if (!CBS_get_u16_length_prefixed(cbs, &server_name_list))
                 goto err;
 
         if (!CBS_get_u8(&server_name_list, &name_type))
                 goto err;
+
         /*
          * RFC 6066 section 3, only one type (host_name) is specified.
          * We do not tolerate unknown types, neither does BoringSSL.
@@ -743,17 +779,25 @@ tlsext_sni_server_parse(SSL *s, uint16_t msg_type, CBS *cbs, int *alert)
                 goto err;
         }
 
-
-        if (!CBS_get_u16_length_prefixed(&server_name_list, &host_name))
-                goto err;
         /*
          * RFC 6066 section 3 specifies a host name must be at least 1 byte
          * so 0 length is a decode error.
          */
+        if (!CBS_get_u16_length_prefixed(&server_name_list, &host_name))
+                goto err;
         if (CBS_len(&host_name) < 1)
                 goto err;
 
-        if (!tlsext_sni_is_valid_hostname(&host_name)) {
+        if (!tlsext_sni_is_valid_hostname(&host_name, &is_ip)) {
+                /*
+                 * Various pieces of software have been known to set the SNI
+                 * host name to an IP address, even though that violates the
+                 * RFC. If this is the case, pretend the SNI extension does
+                 * not exist.
+                 */
+                if (is_ip)
+                        goto done;
+
                 *alert = SSL_AD_ILLEGAL_PARAMETER;
                 goto err;
         }
@@ -777,6 +821,7 @@ tlsext_sni_server_parse(SSL *s, uint16_t msg_type, CBS *cbs, int *alert)
                 }
         }
 
+ done:
         /*
          * RFC 6066 section 3 forbids multiple host names with the same type,
          * therefore we allow only one entry.
diff --git a/src/lib/libssl/ssl_tlsext.h b/src/lib/libssl/ssl_tlsext.h
index 8e0742aa2c..b4c135fdf1 100644
--- a/src/lib/libssl/ssl_tlsext.h
+++ b/src/lib/libssl/ssl_tlsext.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssl_tlsext.h,v 1.26 2020/10/11 01:13:04 guenther Exp $ */
+/* $OpenBSD: ssl_tlsext.h,v 1.27 2021/11/01 16:37:17 jsing Exp $ */
 /*
  * Copyright (c) 2016, 2017 Joel Sing <jsing@openbsd.org>
  * Copyright (c) 2017 Doug Hogan <doug@openbsd.org>
@@ -60,7 +60,7 @@ int tlsext_sni_client_parse(SSL *s, uint16_t msg_type, CBS *cbs, int *alert);
 int tlsext_sni_server_needs(SSL *s, uint16_t msg_type);
 int tlsext_sni_server_build(SSL *s, uint16_t msg_type, CBB *cbb);
 int tlsext_sni_server_parse(SSL *s, uint16_t msg_type, CBS *cbs, int *alert);
-int tlsext_sni_is_valid_hostname(CBS *cbs);
+int tlsext_sni_is_valid_hostname(CBS *cbs, int *is_ip);
 
 int tlsext_supportedgroups_client_needs(SSL *s, uint16_t msg_type);
 int tlsext_supportedgroups_client_build(SSL *s, uint16_t msg_type, CBB *cbb);