Add authentication parameters compat_realm and upn_usename for SSPI

These parameters are available for SSPI authentication only, to make
it possible to make it behave more like "normal gssapi", while
making it possible to maintain compatibility.

compat_realm is on by default, but can be turned off to make the
authentication use the full Kerberos realm instead of the NetBIOS name.

upn_username is off by default, and can be turned on to return the users
Kerberos UPN rather than the SAM-compatible name (a user in Active
Directory can have both a legacy SAM-compatible username and a new
Kerberos one. Normally they are the same, but not always)

Author: Christian Ullrich
Reviewed by: Robbie Harwood, Alvaro Herrera, me

doc/src/sgml/client-auth.sgml

@@ -1106,6 +1106,43 @@ omicron         bryanh                  guest1
       </listitem>
      </varlistentry>
 
+     <varlistentry>
+      <term><literal>compat_realm</literal></term>
+      <listitem>
+       <para>
+        If set to 1, the domain's SAM-compatible name (also known as the
+        NetBIOS name) is used for the <literal>include_realm</literal>
+        option. This is the default. If set to 0, the true realm name from
+        the Kerberos user principal name is used.
+       </para>
+       <para>
+        Do not enable this option unless your server runs under a domain
+        account (this includes virtual service accounts on a domain member
+        system) and all clients authenticating through SSPI are also using
+        domain accounts, or authentication will fail.
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry>
+      <term><literal>upn_username</literal></term>
+      <listitem>
+       <para>
+        If this option is enabled along with <literal>compat_realm</literal>,
+        the user name from the Kerberos UPN is used for authentication. If
+        it is disabled (the default), the SAM-compatible user name is used.
+        By default, these two names are identical for new user accounts.
+       </para>
+       <para>
+        Note that <application>libpq</> uses the SAM-compatible name if no
+        explicit user name is specified. If you use
+        <application>libpq</> or a driver based on it, you should
+        leave this option disabled or explicitly specify user name in the
+        connection string.
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry>
       <term><literal>map</literal></term>
       <listitem>

src/backend/libpq/auth.c

@@ -166,6 +166,11 @@ typedef SECURITY_STATUS
 			(WINAPI * QUERY_SECURITY_CONTEXT_TOKEN_FN) (
 													   PCtxtHandle, void **);
 static int	pg_SSPI_recvauth(Port *port);
+static int pg_SSPI_make_upn(char *accountname,
+				 size_t accountnamesize,
+				 char *domainname,
+				 size_t domainnamesize,
+				 bool update_accountname);
 #endif
 
 /*----------------------------------------------------------------
@@ -1287,6 +1292,17 @@ pg_SSPI_recvauth(Port *port)
 
 	free(tokenuser);
 
+	if (!port->hba->compat_realm)
+	{
+		int			status = pg_SSPI_make_upn(accountname, sizeof(accountname),
+											  domainname, sizeof(domainname),
+											  port->hba->upn_username);
+
+		if (status != STATUS_OK)
+			/* Error already reported from pg_SSPI_make_upn */
+			return status;
+	}
+
 	/*
 	 * Compare realm/domain if requested. In SSPI, always compare case
 	 * insensitive.
@@ -1322,6 +1338,100 @@ pg_SSPI_recvauth(Port *port)
 	else
 		return check_usermap(port->hba->usermap, port->user_name, accountname, true);
 }
+
+/*
+ * Replaces the domainname with the Kerberos realm name,
+ * and optionally the accountname with the Kerberos user name.
+ */
+static int
+pg_SSPI_make_upn(char *accountname,
+				 size_t accountnamesize,
+				 char *domainname,
+				 size_t domainnamesize,
+				 bool update_accountname)
+{
+	char	   *samname;
+	char	   *upname = NULL;
+	char	   *p = NULL;
+	ULONG		upnamesize = 0;
+	size_t		upnamerealmsize;
+	BOOLEAN		res;
+
+	/*
+	 * Build SAM name (DOMAIN\user), then translate to UPN
+	 * (user@kerberos.realm). The realm name is returned in lower case, but
+	 * that is fine because in SSPI auth, string comparisons are always
+	 * case-insensitive.
+	 */
+
+	samname = psprintf("%s\\%s", domainname, accountname);
+	res = TranslateName(samname, NameSamCompatible, NameUserPrincipal,
+						NULL, &upnamesize);
+
+	if ((!res && GetLastError() != ERROR_INSUFFICIENT_BUFFER)
+		|| upnamesize == 0)
+	{
+		pfree(samname);
+		ereport(LOG,
+				(errcode(ERRCODE_INVALID_ROLE_SPECIFICATION),
+				 errmsg("could not translate name")));
+		return STATUS_ERROR;
+	}
+
+	/* upnamesize includes the terminating NUL. */
+	upname = palloc(upnamesize);
+
+	res = TranslateName(samname, NameSamCompatible, NameUserPrincipal,
+						upname, &upnamesize);
+
+	pfree(samname);
+	if (res)
+		p = strchr(upname, '@');
+
+	if (!res || p == NULL)
+	{
+		pfree(upname);
+		ereport(LOG,
+				(errcode(ERRCODE_INVALID_ROLE_SPECIFICATION),
+				 errmsg("could not translate name")));
+		return STATUS_ERROR;
+	}
+
+	/* Length of realm name after the '@', including the NUL. */
+	upnamerealmsize = upnamesize - (p - upname + 1);
+
+	/* Replace domainname with realm name. */
+	if (upnamerealmsize > domainnamesize)
+	{
+		pfree(upname);
+		ereport(LOG,
+				(errcode(ERRCODE_INVALID_ROLE_SPECIFICATION),
+				 errmsg("realm name too long")));
+		return STATUS_ERROR;
+	}
+
+	/* Length is now safe. */
+	strcpy(domainname, p + 1);
+
+	/* Replace account name as well (in case UPN != SAM)? */
+	if (update_accountname)
+	{
+		if ((p - upname + 1) > accountnamesize)
+		{
+			pfree(upname);
+			ereport(LOG,
+					(errcode(ERRCODE_INVALID_ROLE_SPECIFICATION),
+					 errmsg("translated account name too long")));
+			return STATUS_ERROR;
+		}
+
+		*p = 0;
+		strcpy(accountname, upname);
+	}
+
+	pfree(upname);
+	return STATUS_OK;
+}
 #endif   /* ENABLE_SSPI */
 
 

src/backend/libpq/hba.c

@@ -1293,6 +1293,17 @@ parse_hba_line(List *line, int line_num, char *raw_line)
 		parsedline->auth_method == uaSSPI)
 		parsedline->include_realm = true;
 
+	/*
+	 * For SSPI, include_realm defaults to the SAM-compatible domain (aka
+	 * NetBIOS name) and user names instead of the Kerberos principal name for
+	 * compatibility.
+	 */
+	if (parsedline->auth_method == uaSSPI)
+	{
+		parsedline->compat_realm = true;
+		parsedline->upn_username = false;
+	}
+
 	/* Parse remaining arguments */
 	while ((field = lnext(field)) != NULL)
 	{
@@ -1585,6 +1596,24 @@ parse_hba_auth_opt(char *name, char *val, HbaLine *hbaline, int line_num)
 		else
 			hbaline->include_realm = false;
 	}
+	else if (strcmp(name, "compat_realm") == 0)
+	{
+		if (hbaline->auth_method != uaSSPI)
+			INVALID_AUTH_OPTION("compat_realm", gettext_noop("sspi"));
+		if (strcmp(val, "1") == 0)
+			hbaline->compat_realm = true;
+		else
+			hbaline->compat_realm = false;
+	}
+	else if (strcmp(name, "upn_username") == 0)
+	{
+		if (hbaline->auth_method != uaSSPI)
+			INVALID_AUTH_OPTION("upn_username", gettext_noop("sspi"));
+		if (strcmp(val, "1") == 0)
+			hbaline->upn_username = true;
+		else
+			hbaline->upn_username = false;
+	}
 	else if (strcmp(name, "radiusserver") == 0)
 	{
 		struct addrinfo *gai_result;

src/include/libpq/hba.h

@@ -79,6 +79,8 @@ typedef struct HbaLine
 	bool		clientcert;
 	char	   *krb_realm;
 	bool		include_realm;
+	bool		compat_realm;
+	bool		upn_username;
 	char	   *radiusserver;
 	char	   *radiussecret;
 	char	   *radiusidentifier;