libpq: Improve error handling in passwordFromFile()

Previously, passwordFromFile() returned NULL for valid cases (like no
matching password found) and actual errors (two out-of-memory paths).
This made it impossible for its sole caller, pqConnectOptions2(), to
distinguish between these scenarios and fail the connection
appropriately should an out-of-memory error occur.

This patch extends passwordFromFile() to be able to detect both valid
and failure cases, with an error string given back to the caller of the
function.

Out-of-memory failures unlikely happen in the field, so no backpatch is
done.

Author: Joshua Shanks <jjshanks@gmail.com>
Discussion: https://postgr.es/m/CAOxqWDfihFRmhNVdfu8epYTXQRxkCHSOrg+=-ij2c_X3gW=o3g@mail.gmail.com

diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index a3d12931fff309fa2e91fa782989456406ce4bfe..19bbc00666920c057a6a34fc7652d8308c69fe37 100644 (file)
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -501,8 +501,9 @@ static int  parseServiceFile(const char *serviceFile,
                                                         PQExpBuffer errorMessage,
                                                         bool *group_found);
 static char *pwdfMatchesString(char *buf, const char *token);
-static char *passwordFromFile(const char *hostname, const char *port, const char *dbname,
-                                                         const char *username, const char *pgpassfile);
+static char *passwordFromFile(const char *hostname, const char *port,
+                                                         const char *dbname, const char *username,
+                                                         const char *pgpassfile, const char **errmsg);
 static void pgpassfileWarning(PGconn *conn);
 static void default_threadlock(int acquire);
 static bool sslVerifyProtocolVersion(const char *version);
@@ -1454,6 +1455,7 @@ pqConnectOptions2(PGconn *conn)
                                 * least one of them is guaranteed nonempty by now).
                                 */
                                const char *pwhost = conn->connhost[i].host;
+                               const char *password_errmsg = NULL;
 
                                if (pwhost == NULL || pwhost[0] == '\0')
                                        pwhost = conn->connhost[i].hostaddr;
@@ -1463,7 +1465,15 @@ pqConnectOptions2(PGconn *conn)
                                                                         conn->connhost[i].port,
                                                                         conn->dbName,
                                                                         conn->pguser,
-                                                                        conn->pgpassfile);
+                                                                        conn->pgpassfile,
+                                                                        &password_errmsg);
+
+                               if (password_errmsg != NULL)
+                               {
+                                       conn->status = CONNECTION_BAD;
+                                       libpq_append_conn_error(conn, "%s", password_errmsg);
+                                       return false;
+                               }
                        }
                }
        }
@@ -7942,10 +7952,16 @@ pwdfMatchesString(char *buf, const char *token)
        return NULL;
 }
 
-/* Get a password from the password file. Return value is malloc'd. */
+/*
+ * Get a password from the password file. Return value is malloc'd.
+ *
+ * On failure, *errmsg is set to an error to be returned.  It is
+ * left NULL on success, or if no password could be found.
+ */
 static char *
-passwordFromFile(const char *hostname, const char *port, const char *dbname,
-                                const char *username, const char *pgpassfile)
+passwordFromFile(const char *hostname, const char *port,
+                                const char *dbname, const char *username,
+                                const char *pgpassfile, const char **errmsg)
 {
        FILE       *fp;
 #ifndef WIN32
@@ -7953,6 +7969,8 @@ passwordFromFile(const char *hostname, const char *port, const char *dbname,
 #endif
        PQExpBufferData buf;
 
+       *errmsg = NULL;
+
        if (dbname == NULL || dbname[0] == '\0')
                return NULL;
 
@@ -8019,7 +8037,10 @@ passwordFromFile(const char *hostname, const char *port, const char *dbname,
        {
                /* Make sure there's a reasonable amount of room in the buffer */
                if (!enlargePQExpBuffer(&buf, 128))
+               {
+                       *errmsg = libpq_gettext("out of memory");
                        break;
+               }
 
                /* Read some data, appending it to what we already have */
                if (fgets(buf.data + buf.len, buf.maxlen - buf.len, fp) == NULL)
@@ -8058,7 +8079,7 @@ passwordFromFile(const char *hostname, const char *port, const char *dbname,
 
                                if (!ret)
                                {
-                                       /* Out of memory. XXX: an error message would be nice. */
+                                       *errmsg = libpq_gettext("out of memory");
                                        return NULL;
                                }