Verify that rule separators are not empty

The `usbredirfilter_rules_to_string` function always dereferences its separator
arguments, thus requiring at least one character.

Parsing a rule string in `usbredirfilter_string_to_rules` can only work
correctly when there's at least one separator character for both rules and
tokens.

Signed-off-by: Michael Hanselmann <public@hansmi.ch>

2 files changed, 20 insertions, 0 deletions

diff --git a/tests/filter.c b/tests/filter.c
index 311a861..cbdfde8 100644
--- a/tests/filter.c
+++ b/tests/filter.c
@@ -179,6 +179,18 @@ static const struct test test_cases[] = {
         .filter = "0x03,-1,-1,-1,0|3|-1,-1,-1,-1,1",
         .want_retval = -EINVAL,
     },
+    {
+        .name = "empty token separator",
+        .filter = "0x03,-1,-1,-1,0",
+        .token_sep = "",
+        .want_retval = -EINVAL,
+    },
+    {
+        .name = "empty rule separator",
+        .filter = "0x03,-1,-1,-1,0",
+        .rule_sep = "",
+        .want_retval = -EINVAL,
+    },
 };
 
 static void
diff --git a/usbredirparser/usbredirfilter.c b/usbredirparser/usbredirfilter.c
index ee8f8b9..420370c 100644
--- a/usbredirparser/usbredirfilter.c
+++ b/usbredirparser/usbredirfilter.c
@@ -42,6 +42,10 @@ int usbredirfilter_string_to_rules(
     char *buf = NULL;
     const char *r;
 
+    if (strlen(token_sep) == 0 || strlen(rule_sep) == 0) {
+        return -EINVAL;
+    }
+
     *rules_ret = NULL;
     *rules_count_ret = 0;
 
@@ -113,6 +117,10 @@ char *usbredirfilter_rules_to_string(const struct usbredirfilter_rule *rules,
     if (usbredirfilter_verify(rules, rules_count))
         return NULL;
 
+    if (strlen(token_sep) == 0 || strlen(rule_sep) == 0) {
+        return NULL;
+    }
+
     /* We need 28 bytes per rule in the worst case */
     str = malloc(28 * rules_count + 1);
     if (!str)