Allow matching the DN of a client certificate for authentication

Currently we only recognize the Common Name (CN) of a certificate's
subject to be matched against the user name. Thus certificates with
subjects '/OU=eng/CN=fred' and '/OU=sales/CN=fred' will have the same
connection rights. This patch provides an option to match the whole
Distinguished Name (DN) instead of just the CN. On any hba line using
client certificate identity, there is an option 'clientname' which can
have values of 'DN' or 'CN'. The default is 'CN', the current procedure.

The DN is matched against the RFC2253 formatted DN, which looks like
'CN=fred,OU=eng'.

This facility of probably best used in conjunction with an ident map.

Discussion: https://postgr.es/m/92e70110-9273-d93c-5913-0bccb6562740@dunslane.net

Reviewed-By: Michael Paquier, Daniel Gustafsson, Jacob Champion

12 files changed, 243 insertions, 17 deletions

diff --git a/src/backend/libpq/auth.c b/src/backend/libpq/auth.c
index 994251e7d9d..9dc28e19aaf 100644
--- a/src/backend/libpq/auth.c
+++ b/src/backend/libpq/auth.c
@@ -2800,12 +2800,23 @@ static int
 CheckCertAuth(Port *port)
 {
 	int			status_check_usermap = STATUS_ERROR;
+	char	   *peer_username = NULL;
 
 	Assert(port->ssl);
 
+	/* select the correct field to compare */
+	switch (port->hba->clientcertname)
+	{
+		case clientCertDN:
+			peer_username = port->peer_dn;
+			break;
+		case clientCertCN:
+			peer_username = port->peer_cn;
+	}
+
 	/* Make sure we have received a username in the certificate */
-	if (port->peer_cn == NULL ||
-		strlen(port->peer_cn) <= 0)
+	if (peer_username == NULL ||
+		strlen(peer_username) <= 0)
 	{
 		ereport(LOG,
 				(errmsg("certificate authentication failed for user \"%s\": client certificate contains no user name",
@@ -2813,8 +2824,8 @@ CheckCertAuth(Port *port)
 		return STATUS_ERROR;
 	}
 
-	/* Just pass the certificate cn to the usermap check */
-	status_check_usermap = check_usermap(port->hba->usermap, port->user_name, port->peer_cn, false);
+	/* Just pass the certificate cn/dn to the usermap check */
+	status_check_usermap = check_usermap(port->hba->usermap, port->user_name, peer_username, false);
 	if (status_check_usermap != STATUS_OK)
 	{
 		/*
@@ -2824,9 +2835,18 @@ CheckCertAuth(Port *port)
 		 */
 		if (port->hba->clientcert == clientCertFull && port->hba->auth_method != uaCert)
 		{
-			ereport(LOG,
-					(errmsg("certificate validation (clientcert=verify-full) failed for user \"%s\": CN mismatch",
-							port->user_name)));
+			switch (port->hba->clientcertname)
+			{
+				case clientCertDN:
+					ereport(LOG,
+							(errmsg("certificate validation (clientcert=verify-full) failed for user \"%s\": DN mismatch",
+									port->user_name)));
+					break;
+				case clientCertCN:
+					ereport(LOG,
+							(errmsg("certificate validation (clientcert=verify-full) failed for user \"%s\": CN mismatch",
+									port->user_name)));
+			}
 		}
 	}
 	return status_check_usermap;
diff --git a/src/backend/libpq/be-secure-openssl.c b/src/backend/libpq/be-secure-openssl.c
index 5ce3f27855e..40deab13c7d 100644
--- a/src/backend/libpq/be-secure-openssl.c
+++ b/src/backend/libpq/be-secure-openssl.c
@@ -551,22 +551,26 @@ aloop:
 	/* Get client certificate, if available. */
 	port->peer = SSL_get_peer_certificate(port->ssl);
 
-	/* and extract the Common Name from it. */
+	/* and extract the Common Name and Distinguished Name from it. */
 	port->peer_cn = NULL;
+	port->peer_dn = NULL;
 	port->peer_cert_valid = false;
 	if (port->peer != NULL)
 	{
 		int			len;
+		X509_NAME  *x509name = X509_get_subject_name(port->peer);
+		char	   *peer_dn;
+		BIO		   *bio = NULL;
+		BUF_MEM    *bio_buf = NULL;
 
-		len = X509_NAME_get_text_by_NID(X509_get_subject_name(port->peer),
-										NID_commonName, NULL, 0);
+		len = X509_NAME_get_text_by_NID(x509name, NID_commonName, NULL, 0);
 		if (len != -1)
 		{
 			char	   *peer_cn;
 
 			peer_cn = MemoryContextAlloc(TopMemoryContext, len + 1);
-			r = X509_NAME_get_text_by_NID(X509_get_subject_name(port->peer),
-										  NID_commonName, peer_cn, len + 1);
+			r = X509_NAME_get_text_by_NID(x509name, NID_commonName, peer_cn,
+										  len + 1);
 			peer_cn[len] = '\0';
 			if (r != len)
 			{
@@ -590,6 +594,47 @@ aloop:
 
 			port->peer_cn = peer_cn;
 		}
+
+		bio = BIO_new(BIO_s_mem());
+		if (!bio)
+		{
+			pfree(port->peer_cn);
+			port->peer_cn = NULL;
+			return -1;
+		}
+		/*
+		 * RFC2253 is the closest thing to an accepted standard format for
+		 * DNs. We have documented how to produce this format from a
+		 * certificate. It uses commas instead of slashes for delimiters,
+		 * which make regular expression matching a bit easier. Also note that
+		 * it prints the Subject fields in reverse order.
+		 */
+		X509_NAME_print_ex(bio, x509name, 0, XN_FLAG_RFC2253);
+		if (BIO_get_mem_ptr(bio, &bio_buf) <= 0)
+		{
+			BIO_free(bio);
+			pfree(port->peer_cn);
+			port->peer_cn = NULL;
+			return -1;
+		}
+		peer_dn = MemoryContextAlloc(TopMemoryContext, bio_buf->length + 1);
+		memcpy(peer_dn, bio_buf->data, bio_buf->length);
+		len = bio_buf->length;
+		BIO_free(bio);
+		peer_dn[len] = '\0';
+		if (len != strlen(peer_dn))
+		{
+			ereport(COMMERROR,
+					(errcode(ERRCODE_PROTOCOL_VIOLATION),
+					 errmsg("SSL certificate's distinguished name contains embedded null")));
+			pfree(peer_dn);
+			pfree(port->peer_cn);
+			port->peer_cn = NULL;
+			return -1;
+		}
+
+		port->peer_dn = peer_dn;
+
 		port->peer_cert_valid = true;
 	}
 
@@ -618,6 +663,12 @@ be_tls_close(Port *port)
 		pfree(port->peer_cn);
 		port->peer_cn = NULL;
 	}
+
+	if (port->peer_dn)
+	{
+		pfree(port->peer_dn);
+		port->peer_dn = NULL;
+	}
 }
 
 ssize_t
diff --git a/src/backend/libpq/be-secure.c b/src/backend/libpq/be-secure.c
index bb603ad209b..8ef083200ac 100644
--- a/src/backend/libpq/be-secure.c
+++ b/src/backend/libpq/be-secure.c
@@ -120,8 +120,9 @@ secure_open_server(Port *port)
 	r = be_tls_open_server(port);
 
 	ereport(DEBUG2,
-			(errmsg_internal("SSL connection from \"%s\"",
-					port->peer_cn ? port->peer_cn : "(anonymous)")));
+			(errmsg_internal("SSL connection from DN:\"%s\" CN:\"%s\"",
+							 port->peer_dn ? port->peer_dn : "(anonymous)",
+							 port->peer_cn ? port->peer_cn : "(anonymous)")));
 #endif
 
 	return r;
diff --git a/src/backend/libpq/hba.c b/src/backend/libpq/hba.c
index 9a04c093d5f..feb711a6ef7 100644
--- a/src/backend/libpq/hba.c
+++ b/src/backend/libpq/hba.c
@@ -1753,6 +1753,37 @@ parse_hba_auth_opt(char *name, char *val, HbaLine *hbaline,
 			return false;
 		}
 	}
+	else if (strcmp(name, "clientname") == 0)
+	{
+		if (hbaline->conntype != ctHostSSL)
+		{
+			ereport(elevel,
+					(errcode(ERRCODE_CONFIG_FILE_ERROR),
+					 errmsg("clientname can only be configured for \"hostssl\" rows"),
+					 errcontext("line %d of configuration file \"%s\"",
+								line_num, HbaFileName)));
+			*err_msg = "clientname can only be configured for \"hostssl\" rows";
+			return false;
+		}
+
+		if (strcmp(val, "CN") == 0)
+		{
+			hbaline->clientcertname = clientCertCN;
+		}
+		else if (strcmp(val, "DN") == 0)
+		{
+			hbaline->clientcertname = clientCertDN;
+		}
+		else
+		{
+			ereport(elevel,
+					(errcode(ERRCODE_CONFIG_FILE_ERROR),
+					 errmsg("invalid value for clientname: \"%s\"", val),
+					 errcontext("line %d of configuration file \"%s\"",
+								line_num, HbaFileName)));
+			return false;
+		}
+	}
 	else if (strcmp(name, "pamservice") == 0)
 	{
 		REQUIRE_AUTH_OPTION(uaPAM, "pamservice", "pam");
diff --git a/src/include/libpq/hba.h b/src/include/libpq/hba.h
index 8f09b5638f1..1ec8603da75 100644
--- a/src/include/libpq/hba.h
+++ b/src/include/libpq/hba.h
@@ -71,6 +71,12 @@ typedef enum ClientCertMode
 	clientCertFull
 } ClientCertMode;
 
+typedef enum ClientCertName
+{
+	clientCertCN,
+	clientCertDN
+} ClientCertName;
+
 typedef struct HbaLine
 {
 	int			linenumber;
@@ -101,6 +107,7 @@ typedef struct HbaLine
 	char	   *ldapprefix;
 	char	   *ldapsuffix;
 	ClientCertMode clientcert;
+	ClientCertName clientcertname;
 	char	   *krb_realm;
 	bool		include_realm;
 	bool		compat_realm;
diff --git a/src/include/libpq/libpq-be.h b/src/include/libpq/libpq-be.h
index 891394b0c3e..713c34fedd7 100644
--- a/src/include/libpq/libpq-be.h
+++ b/src/include/libpq/libpq-be.h
@@ -195,6 +195,7 @@ typedef struct Port
 	 */
 	bool		ssl_in_use;
 	char	   *peer_cn;
+	char	   *peer_dn;
 	bool		peer_cert_valid;
 
 	/*
diff --git a/src/test/ssl/Makefile b/src/test/ssl/Makefile
index 4b53fdf6c0d..a9eca9e049d 100644
--- a/src/test/ssl/Makefile
+++ b/src/test/ssl/Makefile
@@ -18,7 +18,7 @@ export with_ssl
 CERTIFICATES := server_ca server-cn-and-alt-names \
 	server-cn-only server-single-alt-name server-multiple-alt-names \
 	server-no-names server-revoked server-ss \
-	client_ca client client-revoked \
+	client_ca client client-dn client-revoked \
 	root_ca
 
 SSLFILES := $(CERTIFICATES:%=ssl/%.key) $(CERTIFICATES:%=ssl/%.crt) \
@@ -91,6 +91,13 @@ ssl/client.crt: ssl/client.key ssl/client_ca.crt
 	openssl x509 -in ssl/temp.crt -out ssl/client.crt # to keep just the PEM cert
 	rm ssl/client.csr ssl/temp.crt
 
+# Client certificate with multi-parth DN, signed by the client CA:
+ssl/client-dn.crt: ssl/client-dn.key ssl/client_ca.crt
+	openssl req -new -key ssl/client-dn.key -out ssl/client-dn.csr -config client-dn.config
+	openssl ca -name client_ca -batch -out ssl/temp.crt -config cas.config -infiles ssl/client-dn.csr
+	openssl x509 -in ssl/temp.crt -out ssl/client-dn.crt # to keep just the PEM cert
+	rm ssl/client-dn.csr ssl/temp.crt
+
 # Another client certificate, signed by the client CA. This one is revoked.
 ssl/client-revoked.crt: ssl/client-revoked.key ssl/client_ca.crt client.config
 	openssl req -new -key ssl/client-revoked.key -out ssl/client-revoked.csr -config client.config
diff --git a/src/test/ssl/client-dn.config b/src/test/ssl/client-dn.config
new file mode 100644
index 00000000000..ee2df54bd6c
--- /dev/null
+++ b/src/test/ssl/client-dn.config
@@ -0,0 +1,16 @@
+# An OpenSSL format CSR config file for creating a client certificate.
+#
+# The certificate is for user "ssltestuser-dn" with a multi-part DN
+
+[ req ]
+distinguished_name     = req_distinguished_name
+prompt                 = no
+
+[ req_distinguished_name ]
+O 					   = PGDG
+0.OU					   = Engineering
+1.OU					   = Testing
+CN                     = ssltestuser-dn
+
+# no extensions in client certs
+[ v3_req ]
diff --git a/src/test/ssl/ssl/client-dn.crt b/src/test/ssl/ssl/client-dn.crt
new file mode 100644
index 00000000000..f2f6a62dadd
--- /dev/null
+++ b/src/test/ssl/ssl/client-dn.crt
@@ -0,0 +1,19 @@
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----
diff --git a/src/test/ssl/ssl/client-dn.key b/src/test/ssl/ssl/client-dn.key
new file mode 100644
index 00000000000..1d67ef04082
--- /dev/null
+++ b/src/test/ssl/ssl/client-dn.key
@@ -0,0 +1,27 @@
+-----BEGIN RSA PRIVATE KEY-----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+-----END RSA PRIVATE KEY-----
diff --git a/src/test/ssl/t/001_ssltests.pl b/src/test/ssl/t/001_ssltests.pl
index bfada03d3eb..adaa1b4e9be 100644
--- a/src/test/ssl/t/001_ssltests.pl
+++ b/src/test/ssl/t/001_ssltests.pl
@@ -17,7 +17,7 @@ if ($ENV{with_ssl} ne 'openssl')
 }
 else
 {
-	plan tests => 100;
+	plan tests => 103;
 }
 
 #### Some configuration
@@ -40,7 +40,7 @@ my $common_connstr;
 my @keys = (
 	"client",     "client-revoked",
 	"client-der", "client-encrypted-pem",
-	"client-encrypted-der");
+	"client-encrypted-der", "client-dn");
 foreach my $key (@keys)
 {
 	copy("ssl/${key}.key", "ssl/${key}_tmp.key")
@@ -453,6 +453,36 @@ test_connect_fails(
 	"certificate authorization fails with correct client cert and wrong password in encrypted PEM format"
 );
 
+
+# correct client cert using whole DN
+my $dn_connstr = "$common_connstr dbname=certdb_dn";
+
+test_connect_ok(
+	$dn_connstr,
+	"user=ssltestuser sslcert=ssl/client-dn.crt sslkey=ssl/client-dn_tmp.key",
+	"certificate authorization succeeds with DN mapping"
+);
+
+# same thing but with a regex
+$dn_connstr = "$common_connstr dbname=certdb_dn_re";
+
+test_connect_ok(
+	$dn_connstr,
+	"user=ssltestuser sslcert=ssl/client-dn.crt sslkey=ssl/client-dn_tmp.key",
+	"certificate authorization succeeds with DN regex mapping"
+);
+
+# same thing but using explicit CN
+$dn_connstr = "$common_connstr dbname=certdb_cn";
+
+test_connect_ok(
+	$dn_connstr,
+	"user=ssltestuser sslcert=ssl/client-dn.crt sslkey=ssl/client-dn_tmp.key",
+	"certificate authorization succeeds with CN mapping"
+);
+
+
+
 TODO:
 {
 	# these tests are left here waiting on us to get better pty support
diff --git a/src/test/ssl/t/SSLServer.pm b/src/test/ssl/t/SSLServer.pm
index 5ec5e0dac88..c494c1ad1cb 100644
--- a/src/test/ssl/t/SSLServer.pm
+++ b/src/test/ssl/t/SSLServer.pm
@@ -109,6 +109,9 @@ sub configure_test_server_for_ssl
 	$node->psql('postgres', "CREATE USER yetanotheruser");
 	$node->psql('postgres', "CREATE DATABASE trustdb");
 	$node->psql('postgres', "CREATE DATABASE certdb");
+	$node->psql('postgres', "CREATE DATABASE certdb_dn");
+	$node->psql('postgres', "CREATE DATABASE certdb_dn_re");
+	$node->psql('postgres', "CREATE DATABASE certdb_cn");
 	$node->psql('postgres', "CREATE DATABASE verifydb");
 
 	# Update password of each user as needed.
@@ -217,7 +220,20 @@ sub configure_hba_for_ssl
 	  "hostssl verifydb        yetanotheruser  $servercidr            $authmethod        clientcert=verify-ca\n";
 	print $hba
 	  "hostssl certdb          all             $servercidr            cert\n";
+	print $hba
+	  "hostssl certdb_dn       all             $servercidr            cert clientname=DN map=dn\n",
+	  "hostssl certdb_dn_re    all             $servercidr            cert clientname=DN map=dnre\n",
+	  "hostssl certdb_cn       all             $servercidr            cert clientname=CN map=cn\n";
 	close $hba;
+
+	# Also set the ident maps. Note: fields with commas must be quoted
+	open my $map, ">", "$pgdata/pg_ident.conf";
+	print $map
+	  "# MAPNAME       SYSTEM-USERNAME                           PG-USERNAME\n",
+	  "dn             \"CN=ssltestuser-dn,OU=Testing,OU=Engineering,O=PGDG\"    ssltestuser\n",
+	  "dnre           \"/^.*OU=Testing,.*\$\"                    ssltestuser\n",
+	  "cn              ssltestuser-dn                            ssltestuser\n";
+
 	return;
 }