From 919d0fd3c8394b0988c0b4f81c081a20f25a8e87 Mon Sep 17 00:00:00 2001 From: Tom Gundersen Date: Mon, 20 Jul 2015 16:01:03 +0200 Subject: [PATCH] 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. --- src/shared/dns-domain.c | 62 ++++++++++++++++++++++++++++++++++++++ src/shared/dns-domain.h | 1 + src/test/test-dns-domain.c | 41 +++++++++++++++++++++++++ 3 files changed, 104 insertions(+) diff --git a/src/shared/dns-domain.c b/src/shared/dns-domain.c index a2b9124a9..8a0dec154 100644 --- a/src/shared/dns-domain.c +++ b/src/shared/dns-domain.c @@ -114,6 +114,68 @@ int dns_label_unescape(const char **name, char *dest, size_t sz) { return r; } +/* @label_terminal: terminal character of a label, updated to point to the terminal character of + * the previous label (always skipping one dot) or to NULL if there are no more + * labels. */ +int dns_label_unescape_suffix(const char *name, const char **label_terminal, char *dest, size_t sz) { + const char *terminal; + int r; + + assert(name); + assert(label_terminal); + assert(dest); + + /* no more labels */ + if (!*label_terminal) { + if (sz >= 1) + *dest = 0; + + return 0; + } + + assert(**label_terminal == '.' || **label_terminal == 0); + + /* skip current terminal character */ + terminal = *label_terminal - 1; + + /* point name to the last label, and terminal to the preceding terminal symbol (or make it a NULL pointer) */ + for (;;) { + if (terminal < name) { + /* reached the first label, so indicate that there are no more */ + terminal = NULL; + break; + } + + /* find the start of the last label */ + if (*terminal == '.') { + const char *y; + unsigned slashes = 0; + + for (y = terminal - 1; y >= name && *y == '\\'; y--) + slashes ++; + + if (slashes % 2 == 0) { + /* the '.' was not escaped */ + name = terminal + 1; + break; + } else { + terminal = y; + continue; + } + } + + terminal --; + } + + r = dns_label_unescape(&name, dest, sz); + if (r < 0) + return r; + + *label_terminal = terminal; + + return r; +} + int dns_label_escape(const char *p, size_t l, char **ret) { _cleanup_free_ char *s = NULL; char *q; diff --git a/src/shared/dns-domain.h b/src/shared/dns-domain.h index 4d9a54e59..4ee10ab9e 100644 --- a/src/shared/dns-domain.h +++ b/src/shared/dns-domain.h @@ -29,6 +29,7 @@ #define DNS_NAME_MAX 255 int dns_label_unescape(const char **name, char *dest, size_t sz); +int dns_label_unescape_suffix(const char *name, const char **label_end, char *dest, size_t sz); int dns_label_escape(const char *p, size_t l, char **ret); int dns_label_apply_idna(const char *encoded, size_t encoded_size, char *decoded, size_t decoded_max); 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(); -- 2.30.2