Merge branch 'maint'

8 files changed, 609 insertions, 1 deletions

diff --git a/lib/public_key/doc/src/public_key.xml b/lib/public_key/doc/src/public_key.xml
index c503230d70..37aa05e0fd 100644
--- a/lib/public_key/doc/src/public_key.xml
+++ b/lib/public_key/doc/src/public_key.xml
@@ -757,6 +757,39 @@ fun(#'DistributionPoint'{}, #'CertificateList'{},
   </func> 
 
   <func>
+    <name>pkix_verify_hostname(Cert, ReferenceIDs) -> boolean()</name>
+    <name>pkix_verify_hostname(Cert, ReferenceIDs, Opts) -> boolean()</name>
+    <fsummary>Verifies that a PKIX x.509 certificate <i>presented identifier</i> (e.g hostname) is
+    an expected one.</fsummary>
+    <type>
+      <v>Cert = der_encoded() | #'OTPCertificate'{} </v>
+      <v>ReferenceIDs = [ RefID ]</v>
+      <v>RefID = {IdType,string()}</v>
+      <v>IdType = dns_id | srv_id | uri_id</v>
+      <v>Opts = [ PvhOpt() ]</v>
+      <v>PvhOpt = [MatchOpt | FailCallBackOpt | FqdnExtractOpt]</v>
+      <v>MatchOpt = {fun(RefId | FQDN::string(), PresentedID) -> boolean() | default}</v>
+      <v>PresentedID = {dNSName,string()} | {uniformResourceIdentifier,string()}</v>
+      <v>FailCallBackOpt = {fail_callback, fun(#'OTPCertificate'{}) -> boolean()}</v>
+      <v>FqdnExtractOpt = {fqdn_fun, fun(RefID) -> FQDN::string() | default | undefined}</v>
+    </type>
+    <desc>
+      <p>This function checks that the <i>Presented Identifier</i> (e.g hostname) in a peer certificate
+      conforms with the Expected Identifier that the client wants to connect to.
+      This functions is intended to be added as an extra client check to the peer certificate when performing
+      <seealso marker="public_key:public_key#pkix_path_validation-3">public_key:pkix_path_validation/3</seealso>
+      </p>
+      <p>See <url href="https://tools.ietf.org/html/rfc6125">RFC 6125</url>
+      for detailed information about hostname verification.
+      The <seealso marker="using_public_key#verify_hostname">User's Manual</seealso>
+      and
+      <seealso marker="using_public_key#verify_hostname_examples">code examples</seealso>
+      describes this function more detailed.
+      </p>
+    </desc>
+  </func>
+
+  <func>
     <name>sign(Msg, DigestType, Key) -> binary()</name>
     <fsummary>Creates a digital signature.</fsummary>
     <type>
diff --git a/lib/public_key/doc/src/using_public_key.xml b/lib/public_key/doc/src/using_public_key.xml
index e3a1eed4be..417d479da3 100644
--- a/lib/public_key/doc/src/using_public_key.xml
+++ b/lib/public_key/doc/src/using_public_key.xml
@@ -417,6 +417,259 @@ true = public_key:verify(Digest, none, Signature, PublicKey),</code>
     
   </section>
   
+ <section>
+   <marker id="verify_hostname"></marker>
+   <title>Verifying a certificate hostname</title>
+   <section>
+     <title>Background</title>
+     <p>When a client checks a server certificate there are a number of checks available like
+     checks that the certificate is not revoked, not forged or not out-of-date.
+     </p>
+     <p>There are however attacks that are not detected by those checks. Suppose a bad guy has
+     succeded with a DNS infection. Then the client could belive it is connecting to one host but
+     ends up at another but evil one. Though it is evil, it could have a perfectly legal
+     certificate! The certificate has a valid signature, it is not revoked, the certificate chain
+     is not faked and has a trusted root and so on.
+     </p>
+     <p>To detect that the server is not the intended one, the client must additionaly perform
+     a <i>hostname verification</i>. This procedure is described in
+     <url href="https://tools.ietf.org/html/rfc6125">RFC 6125</url>. The idea is that the certificate
+     lists the hostnames it could be fetched from. This is checked by the certificate issuer when
+     the certificate is signed. So if the certificate is issued by a trusted root the client 
+     could trust the host names signed in it.
+     </p>
+     <p>There is a default hostname matching procedure defined in
+     <url href="https://tools.ietf.org/html/rfc6125#section-6">RFC 6125, section 6</url>
+     as well as protocol dependent variations defined in
+     <url href="https://tools.ietf.org/html/rfc6125#appendix-B">RFC 6125 appendix B</url>.
+     The default procedure is implemented in
+     <seealso marker="public_key:public_key#pkix_verify_hostname-2">public_key:pkix_verify_hostname/2,3</seealso>.
+     It is possible for a client to hook in modified rules using the options list.
+     </p>
+     <p>Some terminology is needed: the certificate presents hostname(s) on which it is valid.
+     Those are called <i>Presented IDs</i>. The hostname(s) the client belives it connects to
+     are called <i>Reference IDs</i>. The matching rules aims to verify that there is at least
+     one of the Reference IDs that matches one of the Presented IDs. If not, the verification fails.
+     </p>
+     <p>The IDs contains normal fully qualified domain names like e.g <c>foo.example.com</c>,
+     but IP addresses are not recommended. The rfc describes why this is not recommended as well
+     as security considerations about how to aquire the Reference IDs.
+     </p>
+     <p>Internationalized domain names are not supported.
+     </p>
+   </section>
+   <section>
+     <title>The verification process</title>
+     <p>Traditionally the Presented IDs were found in the <c>Subject</c> certificate field as <c>CN</c>
+     names. This is still quite common. When printing a certificate they show up as:
+     </p>
+     <code>
+ $ openssl x509 -text &lt; cert.pem
+ ...
+ Subject: C=SE, CN=example.com, CN=*.example.com, O=erlang.org
+ ...
+     </code>
+     <p>The example <c>Subject</c> field has one C, two CN and one O part. It is only the
+     CN (Common Name) that is used by hostname verification. The two other (C and O) is not used
+     here even when they contain a domain name like the O part. The C and O parts are defined
+     elsewhere and meaningful only for other functions.
+     </p>
+     <p>In the example the Presented IDs are <c>example.com</c> as well as hostnames matching
+     <c>*.example.com</c>. For example <c>foo.example.com</c> and <c>bar.example.com</c> both
+     matches but not <c>foo.bar.example.com</c>. The name <c>erlang.org</c> matches neither
+     since it is not a CN.
+     </p>
+     <p>In case where the Presented IDs are fetched from the <c>Subject</c> certificate field, the
+     names may contain wildcard characters. The function handles this as defined in
+     <url href="https://tools.ietf.org/html/rfc6125#section-6.4.3">chapter 6.4.3 in RFC 6125</url>.
+     </p>
+     <p>There may only be one wildcard character and that is in the first label, for example:
+     <c>*.example.com</c>. This matches <c>foo.example.com</c> but neither <c>example.com</c> nor
+     <c>foo.bar.example.com</c>.
+     </p>
+     <p>There may be label characters before or/and after the wildcard. For example:
+     <c>a*d.example.com</c> matches <c>abcd.example.com</c> and <c>ad.example.com</c>,
+     but not <c>ab.cd.example.com</c>.
+     </p>
+     <p>In the previous example there is no indication of which protocols are expected. So a client
+     has no indication of whether it is a web server, an ldap server or maybe a sip server it is
+     connected to.
+     There are fields in the certificate that can indicate this. To be more exact, the rfc
+     introduces the usage of the <c>X509v3 Subject Alternative Name</c> in the <c>X509v3 extensions</c>
+     field:
+     </p>
+     <code>
+ $ openssl x509 -text &lt; cert.pem
+ ...
+ X509v3 extensions:
+     X509v3 Subject Alternative Name:
+         DNS:kb.example.org, URI:https://www.example.org
+ ...
+     </code>
+     <p>Here <c>kb.example.org</c> serves any protocol while <c>www.example.org</c> presents a secure
+     web server.
+     </p>
+
+     <p>The next example has both <c>Subject</c> and <c>Subject Alternate Name</c> present:</p>
+     <code>
+ $ openssl x509 -text &lt; cert.pem
+ ...
+ Subject: C=SE, CN=example.com, CN=*.example.com, O=erlang.org
+ ...
+ X509v3 extensions:
+     X509v3 Subject Alternative Name:
+         DNS:kb.example.org, URI:https://www.example.org
+ ...
+     </code>
+     <p>The RFC states that if a certificate defines Reference IDs in a <c>Subject Alternate Name</c>
+     field, the <c>Subject</c> field MUST NOT be used for host name checking, even if it contains
+     valid CN names.
+     Therefore only <c>kb.example.org</c> and <c>https://www.example.org</c> matches. The match fails
+     both for <c>example.com</c> and <c>foo.example.com</c> becuase they are in the <c>Subject</c>
+     field which is not checked because the <c>Subject Alternate Name</c> field is present.
+     </p>
+   </section>
+
+   <section>
+    <marker id="verify_hostname_examples"></marker>
+     <title>Function call examples</title>
+     <note>
+       <p>Other applications like ssl/tls or https might have options that are passed
+       down to the <c>public_key:pkix_verify_hostname</c>. You will probably not
+       have to call it directly</p>
+     </note>
+     <p>Suppose our client expects to connect to the web server https://www.example.net. This
+     URI is therefore the Reference IDs of the client.
+     The call will be:
+     </p>
+     <code>
+ public_key:pkix_verify_hostname(CertFromHost,
+                                 [{uri_id, "https://www.example.net"}
+                                 ]).
+     </code>
+     <p>The call will return <c>true</c> or <c>false</c> depending on the check. The caller
+     do not need to handle the matching rules in the rfc. The matching will proceed as:
+     </p>
+     <list>
+       <item>If there is a <c>Subject Alternate Name</c> field, the <c>{uri_id,string()}</c> in the
+       function call will be compared to any
+       <c>{uniformResourceIdentifier,string()}</c> in the Certificate field.
+       If the two <c>strings()</c> are equal (case insensitive), there is a match.
+       The same applies for any <c>{dns_id,string()}</c> in the call which is compared
+       with all <c>{dNSName,string()}</c> in the Certificate field.
+       </item>
+       <item>If there is NO <c>Subject Alternate Name</c> field, the <c>Subject</c> field will be
+       checked. All <c>CN</c> names will be compared to all hostnames <i>extracted</i> from 
+       <c>{uri_id,string()}</c> and from <c>{dns_id,string()}</c>.
+       </item>
+     </list>
+   </section>
+   <section>
+     <title>Extending the search mechanism</title>
+     <p>The caller can use own extraction and matching rules. This is done with the two options
+     <c>fqdn_fun</c> and <c>match_fun</c>.
+     </p>
+     <section>
+       <title>Hostname extraction</title>
+       <p>The <c>fqdn_fun</c> extracts hostnames (Fully Qualified Domain Names) from uri_id
+       or other ReferenceIDs that are not pre-defined in the public_key function.
+       Suppose you have some URI with a very special protocol-part:
+       <c>myspecial://example.com"</c>. Since this a non-standard URI there will be no hostname 
+       extracted for matching CN-names in the <c>Subject</c>.</p>
+       <p>To "teach" the function how to extract, you can give a fun which replaces the default
+       extraction function.
+       The  <c>fqdn_fun</c> takes one argument and returns
+       either a <c>string()</c> to be matched to each CN-name or the atom <c>default</c> which will invoke
+       the default fqdn extraction function. The return value <c>undefined</c> removes the current
+       URI from the fqdn extraction.
+       </p>
+       <code>
+ ...
+ Extract = fun({uri_id, "myspecial://"++HostName}) -> HostName;
+              (_Else) -> default
+           end,
+ ...	 
+ public_key:pkix_verify_hostname(CertFromHost, RefIDs,
+                                 [{fqdn_fun, Extract}])
+ ...
+       </code>
+     </section>
+     <section>
+       <title>Re-defining the match operations</title>
+       <p>The default matching handles dns_id and uri_id. In an uri_id the value is tested for
+       equality with a value from the <c>Subject Alternate Name</c>. If som other kind of matching
+       is needed, use the  <c>match_fun</c> option.
+       </p>
+       <p>The  <c>match_fun</c> takes two arguments and returns either <c>true</c>,
+       <c>false</c> or <c>default</c>. The value  <c>default</c> will invoke the default
+       match function.
+       </p>
+       <code>
+ ...
+ Match = fun({uri_id,"myspecial://"++A},
+             {uniformResourceIdentifier,"myspecial://"++B}) ->
+                                                    my_match(A,B);
+            (_RefID, _PresentedID) ->
+                                default
+         end,
+ ...
+ public_key:pkix_verify_hostname(CertFromHost, RefIDs,
+                                 [{match_fun, Match}]),
+ ...
+       </code>
+       <p>In case of a match operation between a ReferenceID and a CN value from the <c>Subject</c>
+       field, the first argument to the fun is the extracted hostname from the ReferenceID, and the
+       second argument is the tuple <c>{cn, string()}</c> taken from the <c>Subject</c> field. That
+       makes it possible to have separate matching rules for Presented IDs from the  <c>Subject</c>
+       field and from the <c>Subject Alternate Name</c> field.
+       </p>
+       <p>The default matching transformes the ascii values in strings to lowercase before comparing.
+       The  <c>match_fun</c> is however called without any transfomation applied to the strings.  The
+       reason is to enable the user to do unforseen handling of the strings where the original format
+       is needed.
+       </p>
+     </section>
+   </section>
+   <section>
+     <title>"Pinning" a Certificate</title>
+     <p>The <url href="https://tools.ietf.org/html/rfc6125">RFC 6125</url> defines <i>pinning</i>
+     as:</p>
+     <quote>
+       <p>"The act of establishing a cached name association between
+       the application service's certificate and one of the client's
+       reference identifiers, despite the fact that none of the presented
+       identifiers matches the given reference identifier. ..."
+       </p>
+     </quote>
+     <p>The purpose is to have a mechanism for a human to accept an otherwise faulty Certificate.
+     In for example a web browser, you could get a question like </p>
+     <quote>
+       <p>Warning: you wanted to visit the site www.example.com,
+       but the certificate is for shop.example.com. Accept anyway (yes/no)?"
+       </p>
+     </quote>
+     <p>This could be accomplished with the option <c>fail_callback</c> which will
+     be called if the hostname verification fails:
+     </p>
+     <code>
+ -include_lib("public_key/include/public_key.hrl"). % Record def
+ ...
+ Fail = fun(#'OTPCertificate'{}=C) ->
+              case in_my_cache(C) orelse my_accept(C) of
+                  true ->
+                       enter_my_cache(C),
+                       true;
+                  false ->
+                       false
+         end,
+ ...
+ public_key:pkix_verify_hostname(CertFromHost, RefIDs,
+                                 [{fail_callback, Fail}]),
+ ...
+     </code>
+   </section>
+ </section>
+
   <section>
     <title>SSH Files</title>
     
diff --git a/lib/public_key/src/public_key.erl b/lib/public_key/src/public_key.erl
index 3d6238d998..42b6826404 100644
--- a/lib/public_key/src/public_key.erl
+++ b/lib/public_key/src/public_key.erl
@@ -48,6 +48,7 @@
 	 pkix_issuer_id/2,
 	 pkix_normalize_name/1,
 	 pkix_path_validation/3,
+	 pkix_verify_hostname/2, pkix_verify_hostname/3,
 	 ssh_decode/2, ssh_encode/2,
 	 ssh_hostkey_fingerprint/1, ssh_hostkey_fingerprint/2,
 	 ssh_curvename2oid/1, oid2ssh_curvename/1,
@@ -763,6 +764,76 @@ pkix_crls_validate(OtpCert, DPAndCRLs0, Options) ->
     pkix_crls_validate(OtpCert, DPAndCRLs, DPAndCRLs,
 		       Options, pubkey_crl:init_revokation_state()).
 
+%--------------------------------------------------------------------
+-spec pkix_verify_hostname(Cert :: #'OTPCertificate'{} | binary(),
+			   ReferenceIDs :: [{uri_id | dns_id | oid(),  string()}]) -> boolean().
+
+-spec pkix_verify_hostname(Cert :: #'OTPCertificate'{} | binary(),
+			   ReferenceIDs :: [{uri_id | dns_id | oid(),  string()}],
+			   Options :: proplists:proplist()) -> boolean().
+
+%% Description: Validates a hostname to RFC 6125
+%%--------------------------------------------------------------------
+pkix_verify_hostname(Cert, ReferenceIDs) ->
+    pkix_verify_hostname(Cert, ReferenceIDs, []).
+
+pkix_verify_hostname(BinCert, ReferenceIDs, Options)  when is_binary(BinCert) ->
+    pkix_verify_hostname(pkix_decode_cert(BinCert,otp), ReferenceIDs, Options);
+
+pkix_verify_hostname(Cert = #'OTPCertificate'{tbsCertificate = TbsCert}, ReferenceIDs0, Opts) ->
+    MatchFun = proplists:get_value(match_fun,     Opts, undefined),
+    FailCB   = proplists:get_value(fail_callback, Opts, fun(_Cert) -> false end),
+    FqdnFun  = proplists:get_value(fqdn_fun,      Opts, fun verify_hostname_extract_fqdn_default/1),
+
+    ReferenceIDs = [{T,to_string(V)} || {T,V} <- ReferenceIDs0],
+    PresentedIDs =
+	try lists:keyfind(?'id-ce-subjectAltName',
+			  #'Extension'.extnID,
+			  TbsCert#'OTPTBSCertificate'.extensions)
+	of
+	    #'Extension'{extnValue = ExtVals} ->
+		[{T,to_string(V)} || {T,V} <- ExtVals];
+	    false ->
+		[]
+	catch
+	    _:_ -> []
+	end,
+    %% PresentedIDs example: [{dNSName,"ewstest.ericsson.com"}, {dNSName,"www.ericsson.com"}]}
+    case PresentedIDs of
+	[] ->
+	    %% Fallback to CN-ids [rfc6125, ch6]
+	    case TbsCert#'OTPTBSCertificate'.subject of
+		{rdnSequence,RDNseq} ->
+		    PresentedCNs =
+			[{cn, to_string(V)}
+			 || ATVs <- RDNseq, % RDNseq is list-of-lists
+			    #'AttributeTypeAndValue'{type = ?'id-at-commonName',
+						     value = {_T,V}} <- ATVs
+						% _T = kind of string (teletexString etc)
+			],
+		    %% Example of PresentedCNs:  [{cn,"www.ericsson.se"}]
+		    %% match ReferenceIDs to PresentedCNs
+		    verify_hostname_match_loop(verify_hostname_fqnds(ReferenceIDs, FqdnFun),
+					       PresentedCNs,
+					       MatchFun, FailCB, Cert);
+		
+		_ ->
+		    false
+	    end;
+	_ ->
+	    %% match ReferenceIDs to PresentedIDs
+	    case verify_hostname_match_loop(ReferenceIDs, PresentedIDs,
+					    MatchFun, FailCB, Cert) of
+		false ->
+		    %% Try to extract DNS-IDs from URIs etc
+		    DNS_ReferenceIDs =
+			[{dns_is,X} || X <- verify_hostname_fqnds(ReferenceIDs, FqdnFun)],
+		    verify_hostname_match_loop(DNS_ReferenceIDs, PresentedIDs,
+					       MatchFun, FailCB, Cert);
+		true ->
+		    true
+	    end
+    end.
 
 %%--------------------------------------------------------------------
 -spec ssh_decode(binary(), public_key | ssh_file()) -> [{public_key(), Attributes::list()}]
@@ -1197,3 +1268,96 @@ ascii_to_lower(String) ->
           end)>>
        ||
         <<C>> <= iolist_to_binary(String) >>.
+
+%%%----------------------------------------------------------------
+%%% pkix_verify_hostname help functions
+verify_hostname_extract_fqdn_default({dns_id,S}) ->
+    S;
+verify_hostname_extract_fqdn_default({uri_id,URI}) ->
+    {ok,{https,_,Host,_,_,_}} = http_uri:parse(URI),
+    Host.
+
+
+verify_hostname_fqnds(L, FqdnFun) ->
+    [E || E0 <- L,
+	  E <- [try case FqdnFun(E0) of
+			default -> verify_hostname_extract_fqdn_default(E0);
+                        undefined -> undefined; % will make the "is_list(E)" test fail
+			Other -> Other
+		    end
+		catch _:_-> undefined % will make the "is_list(E)" test fail
+		end],
+	  is_list(E),
+	  E =/= "",
+	  {error,einval} == inet:parse_address(E)
+    ].
+
+
+-define(srvName_OID, {1,3,6,1,4,1,434,2,2,1,37,0}).
+
+verify_hostname_match_default(Ref, Pres) ->
+    verify_hostname_match_default0(to_lower_ascii(Ref), to_lower_ascii(Pres)).
+
+verify_hostname_match_default0(FQDN=[_|_], {cn,FQDN}) -> 
+    not lists:member($*, FQDN);
+verify_hostname_match_default0(FQDN=[_|_], {cn,Name=[_|_]}) -> 
+    [F1|Fs] = string:tokens(FQDN, "."),
+    [N1|Ns] = string:tokens(Name, "."),
+    match_wild(F1,N1) andalso Fs==Ns;
+verify_hostname_match_default0({dns_id,R}, {dNSName,P}) ->
+    R==P;
+verify_hostname_match_default0({uri_id,R}, {uniformResourceIdentifier,P}) ->
+    R==P;
+verify_hostname_match_default0({srv_id,R}, {T,P}) when T == srvName ;
+                                                       T == ?srvName_OID ->
+    R==P;
+verify_hostname_match_default0(_, _) ->
+    false.
+
+
+match_wild(A,     [$*|B]) -> match_wild_suffixes(A, B);
+match_wild([C|A], [ C|B]) -> match_wild(A, B);
+match_wild([],        []) -> true;
+match_wild(_,          _) -> false.
+
+%% Match the parts after the only wildcard by comparing them from the end
+match_wild_suffixes(A, B) -> match_wild_sfx(lists:reverse(A), lists:reverse(B)).
+
+match_wild_sfx([$*|_],      _) -> false; % Bad name (no wildcards alowed)
+match_wild_sfx(_,      [$*|_]) -> false; % Bad pattern (no more wildcards alowed)
+match_wild_sfx([A|Ar], [A|Br]) -> match_wild_sfx(Ar, Br);
+match_wild_sfx(Ar,         []) -> not lists:member($*, Ar); % Chk for bad name (= wildcards)
+match_wild_sfx(_,           _) -> false.
+    
+
+verify_hostname_match_loop(Refs0, Pres0, undefined, FailCB, Cert) ->
+    Pres = lists:map(fun to_lower_ascii/1, Pres0),
+    Refs = lists:map(fun to_lower_ascii/1, Refs0),
+    lists:any(
+      fun(R) ->
+	      lists:any(fun(P) ->
+                                verify_hostname_match_default(R,P) orelse FailCB(Cert)
+			end, Pres)
+      end, Refs);
+verify_hostname_match_loop(Refs, Pres, MatchFun, FailCB, Cert) ->
+    lists:any(
+      fun(R) ->
+	      lists:any(fun(P) ->
+				(case MatchFun(R,P) of
+				     default -> verify_hostname_match_default(R,P);
+				     Bool -> Bool
+				 end) orelse FailCB(Cert)
+			end,
+			Pres)
+      end,
+      Refs).
+
+
+to_lower_ascii(S) when is_list(S) -> lists:map(fun to_lower_ascii/1, S);
+to_lower_ascii({T,S}) -> {T, to_lower_ascii(S)};
+to_lower_ascii(C) when $A =< C,C =< $Z -> C + ($a-$A);
+to_lower_ascii(C) -> C.
+
+to_string(S) when is_list(S) -> S;
+to_string(B) when is_binary(B) -> binary_to_list(B).
+
diff --git a/lib/public_key/test/public_key_SUITE.erl b/lib/public_key/test/public_key_SUITE.erl
index cd24819899..615ff32539 100644
--- a/lib/public_key/test/public_key_SUITE.erl
+++ b/lib/public_key/test/public_key_SUITE.erl
@@ -45,6 +45,9 @@ all() ->
      {group, sign_verify},
      pkix, pkix_countryname, pkix_emailaddress, pkix_path_validation,
      pkix_iso_rsa_oid, pkix_iso_dsa_oid, pkix_crl, general_name,
+     pkix_verify_hostname_cn,
+     pkix_verify_hostname_subjAltName,
+     pkix_verify_hostname_options,
      short_cert_issuer_hash, short_crl_issuer_hash,
      ssh_hostkey_fingerprint_md5_implicit,
      ssh_hostkey_fingerprint_md5,
@@ -814,6 +817,114 @@ pkix_path_validation(Config) when is_list(Config) ->
     ok.
 
 %%--------------------------------------------------------------------
+%% To generate the PEM file contents:
+%%
+%% openssl req -x509 -nodes -newkey rsa:1024 -keyout /dev/null -subj '/C=SE/CN=example.com/CN=*.foo.example.com/CN=a*b.bar.example.com/O=erlang.org' > public_key_SUITE_data/pkix_verify_hostname_cn.pem
+%%
+%% Note that the same pem-file is used in pkix_verify_hostname_options/1
+%%
+%% Subject: C=SE, CN=example.com, CN=*.foo.example.com, CN=a*b.bar.example.com, O=erlang.org
+%% extensions = no subjAltName
+
+pkix_verify_hostname_cn(Config) ->
+    DataDir = proplists:get_value(data_dir, Config),
+    {ok,Bin} = file:read_file(filename:join(DataDir,"pkix_verify_hostname_cn.pem")),
+    Cert = public_key:pkix_decode_cert(element(2,hd(public_key:pem_decode(Bin))), otp),
+
+    %% Check that 1) only CNs are checked,
+    %%            2) an empty label does not match a wildcard and
+    %%            3) a wildcard does not match more than one label
+    false = public_key:pkix_verify_hostname(Cert, [{dns_id,"erlang.org"},
+						   {dns_id,"foo.EXAMPLE.com"},
+						   {dns_id,"b.a.foo.EXAMPLE.com"}]),
+
+    %% Check that a hostname is extracted from a https-uri and used for checking:
+    true =  public_key:pkix_verify_hostname(Cert, [{uri_id,"HTTPS://EXAMPLE.com"}]),
+
+    %% Check wildcard matching one label:
+    true =  public_key:pkix_verify_hostname(Cert, [{dns_id,"a.foo.EXAMPLE.com"}]),
+
+    %% Check wildcard with surrounding chars matches one label:
+    true =  public_key:pkix_verify_hostname(Cert, [{dns_id,"accb.bar.EXAMPLE.com"}]),
+
+    %% Check that a wildcard with surrounding chars matches an empty string:
+    true =  public_key:pkix_verify_hostname(Cert, [{uri_id,"https://ab.bar.EXAMPLE.com"}]).
+
+%%--------------------------------------------------------------------
+%% To generate the PEM file contents:
+%%
+%% openssl req -x509 -nodes -newkey rsa:1024 -keyout /dev/null -extensions SAN -config  public_key_SUITE_data/verify_hostname.conf 2>/dev/null > public_key_SUITE_data/pkix_verify_hostname_subjAltName.pem
+%%
+%% Subject: C=SE, CN=example.com
+%% Subject Alternative Name: DNS:kb.example.org, URI:http://www.example.org, URI:https://wws.example.org
+
+pkix_verify_hostname_subjAltName(Config) ->
+    DataDir = proplists:get_value(data_dir, Config),
+    {ok,Bin} = file:read_file(filename:join(DataDir,"pkix_verify_hostname_subjAltName.pem")),
+    Cert = public_key:pkix_decode_cert(element(2,hd(public_key:pem_decode(Bin))), otp),
+
+    %% Check that neither a uri nor dns hostname matches a CN if subjAltName is present:
+    false = public_key:pkix_verify_hostname(Cert, [{uri_id,"https://example.com"},
+						   {dns_id,"example.com"}]),
+
+    %% Check that a uri_id matches a URI subjAltName:
+    true =  public_key:pkix_verify_hostname(Cert, [{uri_id,"https://wws.example.org"}]),
+
+    %% Check that a dns_id does not match a URI subjAltName:
+    false = public_key:pkix_verify_hostname(Cert, [{dns_id,"www.example.org"},
+						   {dns_id,"wws.example.org"}]),
+
+    %% Check that a dns_id matches a DNS subjAltName:
+    true =  public_key:pkix_verify_hostname(Cert, [{dns_id,"kb.example.org"}]).
+
+%%--------------------------------------------------------------------
+%% Uses the pem-file for pkix_verify_hostname_cn
+%% Subject: C=SE, CN=example.com, CN=*.foo.example.com, CN=a*b.bar.example.com, O=erlang.org
+pkix_verify_hostname_options(Config) ->
+    DataDir = proplists:get_value(data_dir, Config),
+    {ok,Bin} = file:read_file(filename:join(DataDir,"pkix_verify_hostname_cn.pem")),
+    Cert = public_key:pkix_decode_cert(element(2,hd(public_key:pem_decode(Bin))), otp),
+    
+    %% Check that the fail_callback is called and is presented the correct certificate:
+    true = public_key:pkix_verify_hostname(Cert, [{dns_id,"erlang.org"}],
+					   [{fail_callback,
+					     fun(#'OTPCertificate'{}=C) when C==Cert -> 
+						     true; % To test the return value matters
+						(#'OTPCertificate'{}=C) -> 
+						     ct:log("~p:~p: Wrong cert:~n~p~nExpect~n~p",
+							    [?MODULE, ?LINE, C, Cert]),
+						     ct:fail("Wrong cert, see log");
+						(C) -> 
+						     ct:log("~p:~p: Bad cert: ~p",[?MODULE,?LINE,C]),
+						     ct:fail("Bad cert, see log")
+					     end}]),
+    
+    %% Check the callback for user-provided match functions:
+    true =  public_key:pkix_verify_hostname(Cert, [{dns_id,"very.wrong.domain"}],
+					    [{match_fun,
+					      fun("very.wrong.domain", {cn,"example.com"}) ->
+						      true;
+						 (_, _) ->
+						      false
+					      end}]),
+    false = public_key:pkix_verify_hostname(Cert, [{dns_id,"not.example.com"}],
+					    [{match_fun, fun(_, _) -> default end}]),
+    true =  public_key:pkix_verify_hostname(Cert, [{dns_id,"example.com"}],
+					    [{match_fun, fun(_, _) -> default end}]),
+
+    %% Check the callback for user-provided fqdn extraction:
+    true =  public_key:pkix_verify_hostname(Cert, [{uri_id,"some://very.wrong.domain"}],
+					    [{fqdn_fun,
+					      fun({uri_id, "some://very.wrong.domain"}) ->
+						      "example.com";
+						 (_) ->
+						      ""
+					      end}]),
+    true =  public_key:pkix_verify_hostname(Cert, [{uri_id,"https://example.com"}],
+					    [{fqdn_fun, fun(_) -> default end}]),
+    false =  public_key:pkix_verify_hostname(Cert, [{uri_id,"some://very.wrong.domain"}]).
+
+%%--------------------------------------------------------------------
 pkix_iso_rsa_oid() ->
  [{doc, "Test workaround for supporting certs that use ISO oids"
    " 1.3.14.3.2.29 instead of PKIX/PKCS oid"}].
diff --git a/lib/public_key/test/public_key_SUITE_data/pkix_verify_hostname_cn.pem b/lib/public_key/test/public_key_SUITE_data/pkix_verify_hostname_cn.pem
new file mode 100644
index 0000000000..9f7b428f9a
--- /dev/null
+++ b/lib/public_key/test/public_key_SUITE_data/pkix_verify_hostname_cn.pem
@@ -0,0 +1,17 @@
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----
diff --git a/lib/public_key/test/public_key_SUITE_data/pkix_verify_hostname_subjAltName.pem b/lib/public_key/test/public_key_SUITE_data/pkix_verify_hostname_subjAltName.pem
new file mode 100644
index 0000000000..83e1ad37b3
--- /dev/null
+++ b/lib/public_key/test/public_key_SUITE_data/pkix_verify_hostname_subjAltName.pem
@@ -0,0 +1,14 @@
+-----BEGIN CERTIFICATE-----
+MIICEjCCAXugAwIBAgIJANwliLph5EiAMA0GCSqGSIb3DQEBCwUAMCMxCzAJBgNV
+BAYTAlNFMRQwEgYDVQQDEwtleGFtcGxlLmNvbTAeFw0xNjEyMjAxNTEyMjRaFw0x
+NzAxMTkxNTEyMjRaMCMxCzAJBgNVBAYTAlNFMRQwEgYDVQQDEwtleGFtcGxlLmNv
+bTCBnzANBgkqhkiG9w0BAQEFAAOBjQAwgYkCgYEAydstIN157w8QxkVaOl3wm81j
+fgZ8gqO3BXkECPF6bw5ewLlmePL6Qs4RypsaRe7cKJ9rHFlwhpdcYkxWSWEt2N7Z
+Ry3N4SjuU04ohWbYgy3ijTt7bJg7jOV1Dh56BnI4hwhQj0oNFizNZOeRRfEzdMnS
++uk03t/Qre2NS7KbwnUCAwEAAaNOMEwwSgYDVR0RBEMwQYIOa2IuZXhhbXBsZS5v
+cmeGFmh0dHA6Ly93d3cuZXhhbXBsZS5vcmeGF2h0dHBzOi8vd3dzLmV4YW1wbGUu
+b3JnMA0GCSqGSIb3DQEBCwUAA4GBAKqFqW5gCso422bXriCBJoygokOTTOw1Rzpq
+K8Mm0B8W9rrW9OTkoLEcjekllZcUCZFin2HovHC5HlHZz+mQvBI1M6sN2HVQbSzS
+EgL66U9gwJVnn9/U1hXhJ0LO28aGbyE29DxnewNR741dWN3oFxCdlNaO6eMWaEsO
+gduJ5sDl
+-----END CERTIFICATE-----
diff --git a/lib/public_key/test/public_key_SUITE_data/verify_hostname.conf b/lib/public_key/test/public_key_SUITE_data/verify_hostname.conf
new file mode 100644
index 0000000000..a28864dc78
--- /dev/null
+++ b/lib/public_key/test/public_key_SUITE_data/verify_hostname.conf
@@ -0,0 +1,16 @@
+[req]
+prompt             = no
+distinguished_name = DN
+
+[DN]
+C=SE
+CN=example.com
+
+[SAN]
+subjectAltName = @alt_names
+
+[alt_names]
+DNS = kb.example.org
+URI.1 = http://www.example.org
+URI.2 = https://wws.example.org
+
diff --git a/lib/ssh/src/ssh_transport.erl b/lib/ssh/src/ssh_transport.erl
index 53e9ef485b..37ec984237 100644
--- a/lib/ssh/src/ssh_transport.erl
+++ b/lib/ssh/src/ssh_transport.erl
@@ -432,7 +432,7 @@ handle_kex_dh_gex_request(#ssh_msg_kex_dh_gex_request{min = Min0,
 		ssh_packet(#ssh_msg_kex_dh_gex_group{p = P, g = G}, Ssh0),
 	    {ok, SshPacket, 
 	     Ssh#ssh{keyex_key = {{Private, Public}, {G, P}},
-		     keyex_info = {Min, Max, NBits}
+		     keyex_info = {Min0, Max0, NBits}
 		    }};
 	{error,_} ->
 	    ssh_connection_handler:disconnect(