ssl: Extend hostname check to fallback to checking IP-address

If no SNI is available and the hostname is an IP-address also check
for IP-address match. This check is not as good as a DNS hostname check
and certificates using IP-address are not recommended.

4 files changed, 47 insertions, 14 deletions

diff --git a/lib/ssl/src/ssl.erl b/lib/ssl/src/ssl.erl
index 4e592c02ec..054e3b7ae3 100644
--- a/lib/ssl/src/ssl.erl
+++ b/lib/ssl/src/ssl.erl
@@ -1003,7 +1003,7 @@ validate_option(server_name_indication = Opt, Value) when is_list(Value) ->
 validate_option(server_name_indication, undefined = Value) ->
     Value;
 validate_option(server_name_indication, disable) ->
-    undefined;
+    disable;
 
 validate_option(sni_hosts, []) ->
     [];
diff --git a/lib/ssl/src/ssl_certificate.erl b/lib/ssl/src/ssl_certificate.erl
index 0dd5e5c5cf..a3333d35e9 100644
--- a/lib/ssl/src/ssl_certificate.erl
+++ b/lib/ssl/src/ssl_certificate.erl
@@ -138,13 +138,8 @@ validate(_, {bad_cert, _} = Reason, _) ->
     {fail, Reason};
 validate(_, valid, UserState) ->
     {valid, UserState};
-validate(Cert, valid_peer, UserState = {client, _,_, Hostname, _, _}) when Hostname =/= undefined ->
-    case public_key:pkix_verify_hostname(Cert, [{dns_id, Hostname}]) of
-        true ->
-            {valid, UserState};
-        false ->
-            {fail, {bad_cert, hostname_check_failed}}
-    end;
+validate(Cert, valid_peer, UserState = {client, _,_, Hostname, _, _}) when Hostname =/= disable ->
+    verify_hostname(Hostname, Cert, UserState);  
 validate(_, valid_peer, UserState) ->    
    {valid, UserState}.
 
@@ -337,3 +332,32 @@ new_trusteded_chain(DerCert, [_ | Rest]) ->
     new_trusteded_chain(DerCert, Rest);
 new_trusteded_chain(_, []) ->
     unknown_ca.
+
+verify_hostname({fallback, Hostname}, Cert, UserState) when is_list(Hostname) ->
+    case public_key:pkix_verify_hostname(Cert, [{dns_id, Hostname}]) of
+        true ->
+            {valid, UserState};
+        false ->
+            case public_key:pkix_verify_hostname(Cert, [{ip, Hostname}]) of
+                true ->
+                    {valid, UserState};
+                false ->
+                    {fail, {bad_cert, hostname_check_failed}}
+            end
+    end;
+
+verify_hostname({fallback, Hostname}, Cert, UserState) ->
+    case public_key:pkix_verify_hostname(Cert, [{ip, Hostname}]) of
+        true ->
+            {valid, UserState};
+        false ->
+            {fail, {bad_cert, hostname_check_failed}}
+    end;
+
+verify_hostname(Hostname, Cert, UserState) ->
+    case public_key:pkix_verify_hostname(Cert, [{dns_id, Hostname}]) of
+        true ->
+            {valid, UserState};
+        false ->
+            {fail, {bad_cert, hostname_check_failed}}
+    end.
diff --git a/lib/ssl/src/ssl_connection.erl b/lib/ssl/src/ssl_connection.erl
index 2dbe08e0a7..2fed7d864f 100644
--- a/lib/ssl/src/ssl_connection.erl
+++ b/lib/ssl/src/ssl_connection.erl
@@ -496,12 +496,13 @@ certify(internal, #certificate{},
 certify(internal, #certificate{} = Cert,
         #state{negotiated_version = Version,
 	       role = Role,
+               host = Host,
 	       cert_db = CertDbHandle,
 	       cert_db_ref = CertDbRef,
 	       crl_db = CRLDbInfo,
 	       ssl_options = Opts} = State, Connection) ->
     case ssl_handshake:certify(Cert, CertDbHandle, CertDbRef, 
-			       Opts, CRLDbInfo, Role) of
+			       Opts, CRLDbInfo, Role, Host) of
         {PeerCert, PublicKeyInfo} ->
 	    handle_peer_cert(Role, PeerCert, PublicKeyInfo,
 			     State#state{client_certificate_requested = false}, Connection);
diff --git a/lib/ssl/src/ssl_handshake.erl b/lib/ssl/src/ssl_handshake.erl
index b1661624b5..0ee9ee3322 100644
--- a/lib/ssl/src/ssl_handshake.erl
+++ b/lib/ssl/src/ssl_handshake.erl
@@ -50,7 +50,7 @@
 	 finished/5,  next_protocol/1]).
 
 %% Handle handshake messages
--export([certify/6, client_certificate_verify/6, certificate_verify/6, verify_signature/5,
+-export([certify/7, client_certificate_verify/6, certificate_verify/6, verify_signature/5,
 	 master_secret/4, server_key_exchange_hash/2, verify_connection/6,
 	 init_handshake_history/0, update_handshake_history/3, verify_server_key/5
 	]).
@@ -389,21 +389,21 @@ verify_signature(_, Hash, {HashAlgo, _SignAlg}, Signature,
 
 %%--------------------------------------------------------------------
 -spec certify(#certificate{}, db_handle(), certdb_ref(), #ssl_options{}, term(),
-	      client | server) ->  {der_cert(), public_key_info()} | #alert{}.
+	      client | server, inet:hostname() | inet:ip_address()) ->  {der_cert(), public_key_info()} | #alert{}.
 %%
 %% Description: Handles a certificate handshake message
 %%--------------------------------------------------------------------
 certify(#certificate{asn1_certificates = ASN1Certs}, CertDbHandle, CertDbRef,
-        Opts, CRLDbHandle, Role) ->    
+        Opts, CRLDbHandle, Role, Host) ->    
 
+    ServerName = server_name(Opts#ssl_options.server_name_indication, Host, Role),
     [PeerCert | _] = ASN1Certs,       
     try
 	{TrustedCert, CertPath}  =
 	    ssl_certificate:trusted_cert_and_path(ASN1Certs, CertDbHandle, CertDbRef,  
                                                   Opts#ssl_options.partial_chain),
         ValidationFunAndState = validation_fun_and_state(Opts#ssl_options.verify_fun, Role, 
-                                                         CertDbHandle, CertDbRef,  
-                                                         Opts#ssl_options.server_name_indication,
+                                                         CertDbHandle, CertDbRef, ServerName,
                                                          Opts#ssl_options.crl_check, CRLDbHandle, CertPath),
 	case public_key:pkix_path_validation(TrustedCert,
 					     CertPath,
@@ -1528,6 +1528,8 @@ select_shared_curve([Curve | Rest], Curves) ->
 
 sni(undefined) ->
     undefined;
+sni(disable) ->
+    undefined;
 sni(Hostname) ->
     #sni{hostname = Hostname}.
 
@@ -2353,3 +2355,9 @@ available_signature_algs(#hash_sign_algos{hash_sign_algos = ClientHashSigns}, Su
 available_signature_algs(_, _, _, _) -> 
     undefined.
 
+server_name(_, _, server) ->
+    undefined; %% Not interesting to check your own name.
+server_name(undefined, Host, client) ->
+    {fallback, Host}; %% Fallback to Host argument to connect
+server_name(SNI, _, client) ->
+    SNI. %% If Server Name Indication is available