kerneldevice,generic: input pattern to string match is not regex

The input pattern given to the string_match() method is not a regex
pattern and we cannot use it as that, because all the special
characters (e.g. '.') would not be treated correctly.

Also, the prefix matching with the wildcard at the end of the string
needs to be converted to a proper regex wildcard, i.e. '.*'.

This logic also adds support for suffix matching, with a wildcard at
the beginning of the string, e.g. as the ones used for the wwan kernel
device name matching rules (i.e. '*MBIM').

Unit tests are added to cover all cases, most of these tests were
failing without the fixes implemented here.

5 files changed, 179 insertions, 34 deletions

diff --git a/src/kerneldevice/mm-kernel-device-generic.c b/src/kerneldevice/mm-kernel-device-generic.c
index a8f34fed..e0ee7720 100644
--- a/src/kerneldevice/mm-kernel-device-generic.c
+++ b/src/kerneldevice/mm-kernel-device-generic.c
@@ -740,33 +740,6 @@ kernel_device_cmp (MMKernelDevice *a,
 /*****************************************************************************/
 
 static gboolean
-string_match (MMKernelDeviceGeneric *self,
-              const gchar           *str,
-              const gchar           *pattern)
-{
-    g_autoptr(GError)     inner_error = NULL;
-    g_autoptr(GRegex)     regex = NULL;
-    g_autoptr(GMatchInfo) match_info = NULL;
-
-    regex = g_regex_new (pattern, 0, 0, &inner_error);
-    if (!regex) {
-        mm_obj_warn (self, "invalid pattern in rule '%s': %s", pattern, inner_error->message);
-        return FALSE;
-    }
-    g_regex_match_full (regex, str, -1, 0, 0, &match_info, &inner_error);
-    if (inner_error) {
-        mm_obj_warn (self, "couldn't apply pattern match in rule '%s': %s", pattern, inner_error->message);
-        return FALSE;
-    }
-
-    if (!g_match_info_matches (match_info))
-        return FALSE;
-
-    mm_obj_dbg (self, "pattern '%s' matched: '%s'", pattern, str);
-    return TRUE;
-}
-
-static gboolean
 check_condition (MMKernelDeviceGeneric *self,
                  MMUdevRuleMatch       *match)
 {
diff --git a/src/kerneldevice/mm-kernel-device-helpers.c b/src/kerneldevice/mm-kernel-device-helpers.c
index 5ed25efc..af6aed7f 100644
--- a/src/kerneldevice/mm-kernel-device-helpers.c
+++ b/src/kerneldevice/mm-kernel-device-helpers.c
@@ -65,29 +65,81 @@ mm_kernel_device_get_lower_device_name (const gchar *sysfs_path)
 
 /******************************************************************************/
 
+static gchar *
+build_string_match_pattern (const gchar *str)
+{
+    GString     *regex_pattern;
+    const gchar *str_start;
+    gsize        len;
+    gchar       *aux;
+    gboolean     prefix_match = FALSE;
+    gboolean     suffix_match = FALSE;
+
+    /* We allow prefix and suffix matches given as input, by means of the
+     * single '*' character given either at the beginning or the end of the
+     * string. If given in another place, it will assumed to be explicitly
+     * the '*' character, not a catch-all indication. */
+
+    regex_pattern = g_string_new (NULL);
+
+    /* suffix match? */
+    if (str[0] == '*') {
+        str_start = &str[1];
+        suffix_match = TRUE;
+    } else
+        str_start = str;
+
+    /* prefix match? */
+    len = strlen (str_start);
+    if (len > 0 && str_start[len - 1] == '*') {
+        len--;
+        prefix_match = TRUE;
+    }
+
+    /* match start of string */
+    g_string_append (regex_pattern, "^");
+
+    if (suffix_match)
+        g_string_append (regex_pattern, ".*");
+
+    aux = g_regex_escape_string (str_start, len);
+    g_string_append (regex_pattern, aux);
+
+    if (prefix_match)
+        g_string_append (regex_pattern, ".*");
+
+    /* match end of string */
+    g_string_append (regex_pattern, "$");
+
+    return g_string_free (regex_pattern, FALSE);
+}
+
 gboolean
 mm_kernel_device_generic_string_match (const gchar *str,
                                        const gchar *pattern,
                                        gpointer     log_object)
 {
-    g_autoptr(GError)     inner_error = NULL;
-    g_autoptr(GRegex)     regex = NULL;
-    g_autoptr(GMatchInfo) match_info = NULL;
+    g_autoptr(GError)      inner_error = NULL;
+    g_autoptr(GRegex)      regex = NULL;
+    g_autoptr(GMatchInfo)  match_info = NULL;
+    g_autofree gchar      *regex_pattern = NULL;
+
+    regex_pattern = build_string_match_pattern (pattern);
 
-    regex = g_regex_new (pattern, 0, 0, &inner_error);
+    regex = g_regex_new (regex_pattern, G_REGEX_UNGREEDY, 0, &inner_error);
     if (!regex) {
-        mm_obj_warn (log_object, "invalid pattern in rule '%s': %s", pattern, inner_error->message);
+        mm_obj_warn (log_object, "invalid pattern in rule '%s': %s", regex_pattern, inner_error->message);
         return FALSE;
     }
     g_regex_match_full (regex, str, -1, 0, 0, &match_info, &inner_error);
     if (inner_error) {
-        mm_obj_warn (log_object, "couldn't apply pattern match in rule '%s': %s", pattern, inner_error->message);
+        mm_obj_warn (log_object, "couldn't apply pattern match in rule '%s': %s", regex_pattern, inner_error->message);
         return FALSE;
     }
 
     if (!g_match_info_matches (match_info))
         return FALSE;
 
-    mm_obj_dbg (log_object, "pattern '%s' matched: '%s'", pattern, str);
+    mm_obj_dbg (log_object, "pattern '%s' matched: '%s'", regex_pattern, str);
     return TRUE;
 }
diff --git a/src/tests/Makefile.am b/src/tests/Makefile.am
index 26a05fa3..617d6128 100644
--- a/src/tests/Makefile.am
+++ b/src/tests/Makefile.am
@@ -58,6 +58,7 @@ noinst_PROGRAMS = \
 	test-sms-part-cdma \
 	test-udev-rules \
 	test-error-helpers \
+	test-kernel-device-helpers \
 	$(NULL)
 
 if WITH_QMI
diff --git a/src/tests/meson.build b/src/tests/meson.build
index c059ae2d..ff4392d1 100644
--- a/src/tests/meson.build
+++ b/src/tests/meson.build
@@ -5,6 +5,7 @@ test_units = {
   'at-serial-port': libport_dep,
   'charsets': libhelpers_dep,
   'error-helpers': libhelpers_dep,
+  'kernel-device-helpers': libkerneldevice_dep,
   'modem-helpers': libhelpers_dep,
   'sms-part-3gpp': libhelpers_dep,
   'sms-part-cdma': libhelpers_dep,
diff --git a/src/tests/test-kernel-device-helpers.c b/src/tests/test-kernel-device-helpers.c
new file mode 100644
index 00000000..3cbe1d91
--- /dev/null
+++ b/src/tests/test-kernel-device-helpers.c
@@ -0,0 +1,118 @@
+/* -*- Mode: C; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details:
+ *
+ * Copyright (C) 2021 Aleksander Morgado <aleksander@aleksander.es>
+ */
+
+#include <glib.h>
+#include <glib-object.h>
+#include <string.h>
+#include <stdlib.h>
+#include <locale.h>
+
+#define _LIBMM_INSIDE_MM
+#include <libmm-glib.h>
+
+#include "mm-kernel-device-helpers.h"
+#include "mm-log-test.h"
+
+/*****************************************************************************/
+
+typedef struct {
+    const gchar *pattern;
+    const gchar *str;
+    gboolean     match;
+} StringMatchTest;
+
+static const StringMatchTest string_match_tests[] = {
+    {
+        .pattern = "/sys/devices/pci0000:00/0000:00:1f.6/net/eno1",
+        .str     = "/sys/devices/pci0000:00/0000:00:1f.6/net/eno1",
+        .match   = TRUE,
+    },
+    {
+        .pattern = "/sys/devices/pci0000:00/0000:00:1f.6/net/*",
+        .str     = "/sys/devices/pci0000:00/0000:00:1f.6/net/eno1",
+        .match   = TRUE,
+    },
+    {
+        .pattern = "*MBIM",
+        .str     = "wwan0p1MBIM",
+        .match   = TRUE,
+    },
+    /* Don't match leading extra characters */
+    {
+        .pattern = "/sys/devices/pci0000:00/0000:00:1f.6/net",
+        .str     = "aaaaa/sys/devices/pci0000:00/0000:00:1f.6/net",
+        .match   = FALSE,
+    },
+    /* Don't match trailing extra characters */
+    {
+        .pattern = "/sys/devices/pci0000:00/0000:00:1f.6/net",
+        .str     = "/sys/devices/pci0000:00/0000:00:1f.6/netaaa",
+        .match   = FALSE,
+    },
+    /* The ASTERISK in a pattern given must be treated as a wildcard by
+     * itself, not as "the previous character 0-N times", as the input
+     * pattern is not a regex pattern. */
+    {
+        .pattern = "/sys/devices/pci0000:00/0000:00:1f.6/net/*",
+        .str     = "/sys/devices/pci0000:00/0000:00:1ff6/net",
+        .match   = FALSE,
+    },
+    {
+        .pattern = "/sys/devices/pci0000:00/0000:00:1f.6/net/*",
+        .str     = "/sys/devices/pci0000:00/0000:00:1f.6/netaaa",
+        .match   = FALSE,
+    },
+    /* The DOT in a pattern given must match the exact DOT character,
+     * as the input pattern is not a regex pattern. */
+    {
+        .pattern = "/sys/devices/pci0000:00/0000:00:1f.6/net/eno1",
+        .str     = "/sys/devices/pci0000:00/0000:00:1ff6/net/eno1",
+        .match   = FALSE,
+    },
+};
+
+static void
+test_string_match (void)
+{
+    guint i;
+
+    for (i = 0; i < G_N_ELEMENTS (string_match_tests); i++) {
+        gboolean match;
+
+        match = mm_kernel_device_generic_string_match (string_match_tests[i].str,
+                                                       string_match_tests[i].pattern,
+                                                       NULL);
+        if (match != string_match_tests[i].match)
+            mm_obj_warn (NULL, "string match failure: pattern '%s' should%s match str '%s'",
+                         string_match_tests[i].pattern,
+                         string_match_tests[i].match ? "" : " NOT",
+                         string_match_tests[i].str);
+
+        g_assert_cmpuint (match, ==, string_match_tests[i].match);
+    }
+}
+
+/*****************************************************************************/
+
+int main (int argc, char **argv)
+{
+    setlocale (LC_ALL, "");
+
+    g_test_init (&argc, &argv, NULL);
+
+    g_test_add_func ("/MM/kernel-device-helpers/string-match", test_string_match);
+
+    return g_test_run ();
+}