libq support for sslpassword connection param, DER format keys

This patch providies for support for password protected SSL client
keys in libpq, and for DER format keys, both encrypted and unencrypted.
There is a new connection parameter sslpassword, which is supplied to
the OpenSSL libraries via a callback function. The callback function can
also be set by an application by calling PQgetSSLKeyPassHook(). There is
also a function to retreive the connection setting, PQsslpassword().

Craig Ringer and Andrew Dunstan

Reviewed by: Greg Nancarrow

Discussion: https://postgr.es/m/[email protected]

5 files changed, 124 insertions, 4 deletions

diff --git a/src/interfaces/libpq/exports.txt b/src/interfaces/libpq/exports.txt
index ccec59919b2..53f8ee0fc4b 100644
--- a/src/interfaces/libpq/exports.txt
+++ b/src/interfaces/libpq/exports.txt
@@ -176,3 +176,7 @@ PQresultMemorySize        173
 PQhostaddr                174
 PQgssEncInUse             175
 PQgetgssctx               176
+PQsslpassword			  177
+PQsetSSLKeyPassHook		  178
+PQgetSSLKeyPassHook		  179
+PQdefaultSSLKeyPassHook	  180
diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index dcd86ee8043..5c786360a96 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -351,6 +351,10 @@ static const internalPQconninfoOption PQconninfoOptions[] = {
 		"Target-Session-Attrs", "", 11, /* sizeof("read-write") = 11 */
 	offsetof(struct pg_conn, target_session_attrs)},
 
+	{"sslpassword", NULL, NULL, NULL,
+		"SSL-Client-Key-Password", "*", 20,
+	offsetof(struct pg_conn, sslpassword)},
+
 	/* Terminating entry --- MUST BE LAST */
 	{NULL, NULL, NULL, NULL,
 	NULL, NULL, 0}
@@ -4026,6 +4030,8 @@ freePGconn(PGconn *conn)
 		free(conn->target_session_attrs);
 	termPQExpBuffer(&conn->errorMessage);
 	termPQExpBuffer(&conn->workBuffer);
+	if (conn->sslpassword)
+		free(conn->sslpassword);
 
 	free(conn);
 
@@ -6545,6 +6551,14 @@ PQport(const PGconn *conn)
 }
 
 char *
+PQsslpassword(const PGconn *conn)
+{
+	if (!conn)
+		return NULL;
+	return conn->sslpassword;
+}
+
+char *
 PQtty(const PGconn *conn)
 {
 	if (!conn)
diff --git a/src/interfaces/libpq/fe-secure-openssl.c b/src/interfaces/libpq/fe-secure-openssl.c
index c8dddfb5fdb..cba81f63c0d 100644
--- a/src/interfaces/libpq/fe-secure-openssl.c
+++ b/src/interfaces/libpq/fe-secure-openssl.c
@@ -70,6 +70,7 @@ static int	initialize_SSL(PGconn *conn);
 static PostgresPollingStatusType open_client_SSL(PGconn *);
 static char *SSLerrmessage(unsigned long ecode);
 static void SSLerrfree(char *buf);
+static int PQssl_passwd_cb(char *buf, int size, int rwflag, void *userdata);
 
 static int	my_sock_read(BIO *h, char *buf, int size);
 static int	my_sock_write(BIO *h, const char *buf, int size);
@@ -93,6 +94,7 @@ static long win32_ssl_create_mutex = 0;
 #endif
 #endif							/* ENABLE_THREAD_SAFETY */
 
+static PQsslKeyPassHook_type PQsslKeyPassHook = NULL;
 
 /* ------------------------------------------------------------ */
 /*			 Procedures common to all secure sessions			*/
@@ -818,6 +820,26 @@ initialize_SSL(PGconn *conn)
 		return -1;
 	}
 
+	/*
+	 * Delegate the client cert password prompt to the libpq wrapper
+	 * callback if any is defined.
+	 *
+	 * If the application hasn't installed its own and the sslpassword
+	 * parameter is non-null, we install ours now to make sure we
+	 * supply PGconn->sslpassword to OpenSSL instead of letting it
+	 * prompt on stdin.
+	 *
+	 * This will replace OpenSSL's default PEM_def_callback (which
+	 * prompts on stdin), but we're only setting it for this SSL
+	 * context so it's harmless.
+	 */
+	if (PQsslKeyPassHook
+		|| (conn->sslpassword && strlen(conn->sslpassword) > 0))
+	{
+		SSL_CTX_set_default_passwd_cb(SSL_context, PQssl_passwd_cb);
+		SSL_CTX_set_default_passwd_cb_userdata(SSL_context, conn);
+	}
+
 	/* Disable old protocol versions */
 	SSL_CTX_set_options(SSL_context, SSL_OP_NO_SSLv2 | SSL_OP_NO_SSLv3);
 
@@ -1123,11 +1145,29 @@ initialize_SSL(PGconn *conn)
 		{
 			char	   *err = SSLerrmessage(ERR_get_error());
 
-			printfPQExpBuffer(&conn->errorMessage,
-							  libpq_gettext("could not load private key file \"%s\": %s\n"),
-							  fnbuf, err);
+			/*
+			 * We'll try to load the file in DER (binary ASN.1) format, and if
+			 * that fails too, report the original error. This could mask
+			 * issues where there's something wrong with a DER-format cert, but
+			 * we'd have to duplicate openssl's format detection to be smarter
+			 * than this. We can't just probe for a leading -----BEGIN because
+			 * PEM can have leading non-matching lines and blanks. OpenSSL
+			 * doesn't expose its get_name(...) and its PEM routines don't
+			 * differentiate between failure modes in enough detail to let us
+			 * tell the difference between "not PEM, try DER" and "wrong
+			 * password".
+			 */
+			if (SSL_use_PrivateKey_file(conn->ssl, fnbuf, SSL_FILETYPE_ASN1) != 1)
+			{
+				printfPQExpBuffer(&conn->errorMessage,
+								  libpq_gettext("could not load private key file \"%s\": %s\n"),
+								  fnbuf, err);
+				SSLerrfree(err);
+				return -1;
+			}
+
 			SSLerrfree(err);
-			return -1;
+
 		}
 	}
 
@@ -1580,3 +1620,54 @@ my_SSL_set_fd(PGconn *conn, int fd)
 err:
 	return ret;
 }
+
+/*
+ * This is the default handler to return a client cert password from
+ * conn->sslpassword. Apps may install it explicitly if they want to
+ * prevent openssl from ever prompting on stdin.
+ */
+int
+PQdefaultSSLKeyPassHook(char *buf, int size, PGconn *conn)
+{
+	if (conn->sslpassword)
+	{
+		if (strlen(conn->sslpassword) + 1 > size)
+			fprintf(stderr, libpq_gettext("WARNING: sslpassword truncated"));
+		strncpy(buf, conn->sslpassword, size);
+		buf[size-1] = '\0';
+		return strlen(buf);
+	}
+	else
+	{
+		buf[0] = '\0';
+		return 0;
+	}
+}
+
+PQsslKeyPassHook_type
+PQgetSSLKeyPassHook(void)
+{
+	return PQsslKeyPassHook;
+}
+
+void
+PQsetSSLKeyPassHook(PQsslKeyPassHook_type hook)
+{
+	PQsslKeyPassHook = hook;
+}
+
+/*
+ * Supply a password to decrypt a client certificate.
+ *
+ * This must match OpenSSL type pem_passwd_cb.
+ */
+static int
+PQssl_passwd_cb(char *buf, int size, int rwflag, void *userdata)
+{
+	PGconn *conn = userdata;
+
+	if (PQsslKeyPassHook)
+		return PQsslKeyPassHook(buf, size, conn);
+	else
+		return PQdefaultSSLKeyPassHook(buf, size, conn);
+}
diff --git a/src/interfaces/libpq/libpq-fe.h b/src/interfaces/libpq/libpq-fe.h
index 5f65db30e4f..f39db7780c3 100644
--- a/src/interfaces/libpq/libpq-fe.h
+++ b/src/interfaces/libpq/libpq-fe.h
@@ -317,6 +317,7 @@ extern char *PQpass(const PGconn *conn);
 extern char *PQhost(const PGconn *conn);
 extern char *PQhostaddr(const PGconn *conn);
 extern char *PQport(const PGconn *conn);
+extern char *PQsslpassword(const PGconn *conn);
 extern char *PQtty(const PGconn *conn);
 extern char *PQoptions(const PGconn *conn);
 extern ConnStatusType PQstatus(const PGconn *conn);
@@ -617,6 +618,14 @@ extern int	pg_char_to_encoding(const char *name);
 extern const char *pg_encoding_to_char(int encoding);
 extern int	pg_valid_server_encoding_id(int encoding);
 
+/* == in fe-secure-openssl.c === */
+
+/* Support for overriding sslpassword handling with a callback. */
+typedef int (*PQsslKeyPassHook_type)(char *buf, int size, PGconn *conn);
+extern PQsslKeyPassHook_type PQgetSSLKeyPassHook(void);
+extern void PQsetSSLKeyPassHook(PQsslKeyPassHook_type hook);
+extern int PQdefaultSSLKeyPassHook(char *buf, int size, PGconn *conn);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h
index 64468ab4dab..7f5be7db7a1 100644
--- a/src/interfaces/libpq/libpq-int.h
+++ b/src/interfaces/libpq/libpq-int.h
@@ -512,6 +512,8 @@ struct pg_conn
 
 	/* Buffer for receiving various parts of messages */
 	PQExpBufferData workBuffer; /* expansible string */
+
+	char *sslpassword; /* client key file password */
 };
 
 /* PGcancel stores all data necessary to cancel a connection. A copy of this