shared: dns-name - introduce dns_label_unescape_suffix()

Intended to be called repeatedly, and returns then successive unescaped labels
from the most to the least significant (left to right).

This is slightly inefficient as it scans the string three times (two would be
sufficient): once to find the end of the string, once to find the beginning
of each label and lastly once to do the actual unescaping. The latter two
could be done in one go, but that seemed unnecessarily convoluted.

1 files changed, 41 insertions, 0 deletions

diff --git a/src/test/test-dns-domain.c b/src/test/test-dns-domain.c
index 567c1f6f1..31e110cf0 100644
--- a/src/test/test-dns-domain.c
+++ b/src/test/test-dns-domain.c
@@ -50,6 +50,46 @@ static void test_dns_label_unescape(void) {
         test_dns_label_unescape_one("foobar.", "foobar", 20, 6);
 }
 
+static void test_dns_label_unescape_suffix_one(const char *what, const char *expect1, const char *expect2, size_t buffer_sz, int ret1, int ret2) {
+        char buffer[buffer_sz];
+        const char *label;
+        int r;
+
+        label = what + strlen(what);
+
+        r = dns_label_unescape_suffix(what, &label, buffer, buffer_sz);
+        assert_se(r == ret1);
+        if (r >= 0)
+                assert_se(streq(buffer, expect1));
+
+        r = dns_label_unescape_suffix(what, &label, buffer, buffer_sz);
+        assert_se(r == ret2);
+        if (r >= 0)
+                assert_se(streq(buffer, expect2));
+}
+
+static void test_dns_label_unescape_suffix(void) {
+        test_dns_label_unescape_suffix_one("hallo", "hallo", "", 6, 5, 0);
+        test_dns_label_unescape_suffix_one("hallo", "hallo", "", 4, -ENOSPC, -ENOSPC);
+        test_dns_label_unescape_suffix_one("", "", "", 10, 0, 0);
+        test_dns_label_unescape_suffix_one("hallo\\.foobar", "hallo.foobar", "", 20, 12, 0);
+        test_dns_label_unescape_suffix_one("hallo.foobar", "foobar", "hallo", 10, 6, 5);
+        test_dns_label_unescape_suffix_one("hallo.foobar\n", "foobar", "foobar", 20, -EINVAL, -EINVAL);
+        test_dns_label_unescape_suffix_one("hallo\\", "hallo", "hallo", 20, -EINVAL, -EINVAL);
+        test_dns_label_unescape_suffix_one("hallo\\032 ", "hallo  ", "", 20, 7, 0);
+        test_dns_label_unescape_suffix_one(".", "", "", 20, 0, 0);
+        test_dns_label_unescape_suffix_one("..", "", "", 20, 0, 0);
+        test_dns_label_unescape_suffix_one(".foobar", "foobar", "", 20, 6, -EINVAL);
+        test_dns_label_unescape_suffix_one("foobar.", "", "foobar", 20, 0, 6);
+        test_dns_label_unescape_suffix_one("foo\\\\bar", "foo\\bar", "", 20, 7, 0);
+        test_dns_label_unescape_suffix_one("foo.bar", "bar", "foo", 20, 3, 3);
+        test_dns_label_unescape_suffix_one("foo..bar", "bar", "", 20, 3, -EINVAL);
+        test_dns_label_unescape_suffix_one("foo...bar", "bar", "", 20, 3, -EINVAL);
+        test_dns_label_unescape_suffix_one("foo\\.bar", "foo.bar", "", 20, 7, 0);
+        test_dns_label_unescape_suffix_one("foo\\\\.bar", "bar", "foo\\", 20, 3, 4);
+        test_dns_label_unescape_suffix_one("foo\\\\\\.bar", "foo\\.bar", "", 20, 8, 0);
+}
+
 static void test_dns_label_escape_one(const char *what, size_t l, const char *expect, int ret) {
         _cleanup_free_ char *t = NULL;
         int r;
@@ -212,6 +252,7 @@ static void test_dns_name_reverse(void) {
 int main(int argc, char *argv[]) {
 
         test_dns_label_unescape();
+        test_dns_label_unescape_suffix();
         test_dns_label_escape();
         test_dns_name_normalize();
         test_dns_name_equal();