udev: always use last 11 chars for hash string

This makes the last 11 chars are always preserved for hashed string.
So, it is hard to generate a path which conflicts to another path.

Fixes an issue demonstrated in the previous commit.

diff --git a/src/udev/test-udev-node.c b/src/udev/test-udev-node.c
index d2e2285089375450cfaf48f6e7372ab4b87717c9..010c19acf516a4b470e22ec4b661021c05578058 100644 (file)
--- a/src/udev/test-udev-node.c
+++ b/src/udev/test-udev-node.c
@@ -35,8 +35,16 @@ static void test_udev_node_escape_path(void) {
         test_udev_node_escape_path_one(a, b);
 
         strcpy(a + sizeof(a) - 12 - 9, "N3YhcCqFeID");
+        strcpy(b + sizeof(b) - 12, "L1oK9iKWdmi");
+        test_udev_node_escape_path_one(a, b);
+
+        strcpy(a + sizeof(a) - 12 - 9, "a");
+        strcpy(b + sizeof(b) - 12, "A7oaHBRuuZq");
+        test_udev_node_escape_path_one(a, b);
 
-        test_udev_node_escape_path_one(a, b); /* <-- Ouch. This will pass. Needs to be fixed. */
+        a[sizeof(a) - 12 - 9] = '\0';
+        b[sizeof(a) - 12] = '\0';
+        test_udev_node_escape_path_one(a, b);
 }
 
 int main(int argc, char *argv[]) {

diff --git a/src/udev/udev-node.c b/src/udev/udev-node.c
index a56084de7eb9377ff3f7aee676d4f6f5ac27a5c5..9e529065710d68c3981818777935ec9ad47fd92c 100644 (file)
--- a/src/udev/udev-node.c
+++ b/src/udev/udev-node.c
@@ -219,20 +219,21 @@ size_t udev_node_escape_path(const char *src, char *dest, size_t size) {
 
         assert(src);
         assert(dest);
+        assert(size >= 12);
 
         for (i = 0, j = 0; src[i] != '\0'; i++) {
                 if (src[i] == '/') {
-                        if (j+4 >= size)
+                        if (j+4 >= size - 12 + 1)
                                 goto toolong;
                         memcpy(&dest[j], "\\x2f", 4);
                         j += 4;
                 } else if (src[i] == '\\') {
-                        if (j+4 >= size)
+                        if (j+4 >= size - 12 + 1)
                                 goto toolong;
                         memcpy(&dest[j], "\\x5c", 4);
                         j += 4;
                 } else {
-                        if (j+1 >= size)
+                        if (j+1 >= size - 12 + 1)
                                 goto toolong;
                         dest[j] = src[i];
                         j++;
@@ -247,8 +248,6 @@ toolong:
 
         h = siphash24_string(src, UDEV_NODE_HASH_KEY.bytes);
 
-        assert(size >= 12);
-
         for (unsigned k = 0; k <= 10; k++)
                 dest[size - k - 2] = urlsafe_base64char((h >> (k * 6)) & 63);