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-rw-r--r--src/shared/dns-domain.c139
-rw-r--r--src/shared/dns-domain.h3
-rw-r--r--src/test/test-dns-domain.c2
3 files changed, 98 insertions, 46 deletions
diff --git a/src/shared/dns-domain.c b/src/shared/dns-domain.c
index 09ec6e70a0..7a4093cc47 100644
--- a/src/shared/dns-domain.c
+++ b/src/shared/dns-domain.c
@@ -185,7 +185,11 @@ int dns_label_unescape_suffix(const char *name, const char **label_terminal, cha
int dns_label_escape(const char *p, size_t l, char *dest, size_t sz) {
char *q;
- if (l > DNS_LABEL_MAX)
+ /* DNS labels must be between 1 and 63 characters long. A
+ * zero-length label does not exist. See RFC 2182, Section
+ * 11. */
+
+ if (l <= 0 || l > DNS_LABEL_MAX)
return -EINVAL;
if (sz < 1)
return -ENOSPC;
@@ -198,10 +202,11 @@ int dns_label_escape(const char *p, size_t l, char *dest, size_t sz) {
if (*p == '.' || *p == '\\') {
+ /* Dot or backslash */
+
if (sz < 3)
return -ENOSPC;
- /* Dot or backslash */
*(q++) = '\\';
*(q++) = *p;
@@ -253,7 +258,7 @@ int dns_label_escape_new(const char *p, size_t l, char **ret) {
assert(p);
assert(ret);
- if (l > DNS_LABEL_MAX)
+ if (l <= 0 || l > DNS_LABEL_MAX)
return -EINVAL;
s = new(char, DNS_LABEL_ESCAPED_MAX);
@@ -273,32 +278,52 @@ int dns_label_escape_new(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) {
#ifdef HAVE_LIBIDN
_cleanup_free_ uint32_t *input = NULL;
- size_t input_size;
+ size_t input_size, l;
const char *p;
bool contains_8bit = false;
+ char buffer[DNS_LABEL_MAX+1];
assert(encoded);
assert(decoded);
- assert(decoded_max >= DNS_LABEL_MAX);
+
+ /* Converts an U-label into an A-label */
if (encoded_size <= 0)
- return 0;
+ return -EINVAL;
for (p = encoded; p < encoded + encoded_size; p++)
if ((uint8_t) *p > 127)
contains_8bit = true;
- if (!contains_8bit)
+ if (!contains_8bit) {
+ if (encoded_size > DNS_LABEL_MAX)
+ return -EINVAL;
+
return 0;
+ }
input = stringprep_utf8_to_ucs4(encoded, encoded_size, &input_size);
if (!input)
return -ENOMEM;
- if (idna_to_ascii_4i(input, input_size, decoded, 0) != 0)
+ if (idna_to_ascii_4i(input, input_size, buffer, 0) != 0)
+ return -EINVAL;
+
+ l = strlen(buffer);
+
+ /* Verify that the the result is not longer than one DNS label. */
+ if (l <= 0 || l > DNS_LABEL_MAX)
return -EINVAL;
+ if (l > decoded_max)
+ return -ENOSPC;
+
+ memcpy(decoded, buffer, l);
- return strlen(decoded);
+ /* If there's room, append a trailing NUL byte, but only then */
+ if (decoded_max > l)
+ decoded[l] = 0;
+
+ return (int) l;
#else
return 0;
#endif
@@ -312,11 +337,14 @@ int dns_label_undo_idna(const char *encoded, size_t encoded_size, char *decoded,
uint32_t *output = NULL;
size_t w;
- /* To be invoked after unescaping */
+ /* To be invoked after unescaping. Converts an A-label into an U-label. */
assert(encoded);
assert(decoded);
+ if (encoded_size <= 0 || encoded_size > DNS_LABEL_MAX)
+ return -EINVAL;
+
if (encoded_size < sizeof(IDNA_ACE_PREFIX)-1)
return 0;
@@ -336,11 +364,16 @@ int dns_label_undo_idna(const char *encoded, size_t encoded_size, char *decoded,
if (!result)
return -ENOMEM;
if (w <= 0)
- return 0;
- if (w+1 > decoded_max)
return -EINVAL;
+ if (w > decoded_max)
+ return -ENOSPC;
+
+ memcpy(decoded, result, w);
+
+ /* Append trailing NUL byte if there's space, but only then. */
+ if (decoded_max > w)
+ decoded[w] = 0;
- memcpy(decoded, result, w+1);
return w;
#else
return 0;
@@ -511,24 +544,32 @@ int dns_name_equal(const char *x, const char *y) {
r = dns_label_unescape(&x, la, sizeof(la));
if (r < 0)
return r;
-
- k = dns_label_undo_idna(la, r, la, sizeof(la));
- if (k < 0)
- return k;
- if (k > 0)
- r = k;
+ if (r > 0) {
+ k = dns_label_undo_idna(la, r, la, sizeof(la));
+ if (k < 0)
+ return k;
+ if (k > 0)
+ r = k;
+ }
q = dns_label_unescape(&y, lb, sizeof(lb));
if (q < 0)
return q;
- w = dns_label_undo_idna(lb, q, lb, sizeof(lb));
- if (w < 0)
- return w;
- if (w > 0)
- q = w;
+ if (q > 0) {
+ w = dns_label_undo_idna(lb, q, lb, sizeof(lb));
+ if (w < 0)
+ return w;
+ if (w > 0)
+ q = w;
+ }
+
+ /* If one name had fewer labels than the other, this
+ * will show up as empty label here, which the
+ * strcasecmp() below will properly consider different
+ * from a non-empty label. */
la[r] = lb[q] = 0;
- if (strcasecmp(la, lb))
+ if (strcasecmp(la, lb) != 0)
return false;
}
}
@@ -549,11 +590,13 @@ int dns_name_endswith(const char *name, const char *suffix) {
r = dns_label_unescape(&n, ln, sizeof(ln));
if (r < 0)
return r;
- k = dns_label_undo_idna(ln, r, ln, sizeof(ln));
- if (k < 0)
- return k;
- if (k > 0)
- r = k;
+ if (r > 0) {
+ k = dns_label_undo_idna(ln, r, ln, sizeof(ln));
+ if (k < 0)
+ return k;
+ if (k > 0)
+ r = k;
+ }
if (!saved_n)
saved_n = n;
@@ -561,11 +604,13 @@ int dns_name_endswith(const char *name, const char *suffix) {
q = dns_label_unescape(&s, ls, sizeof(ls));
if (q < 0)
return q;
- w = dns_label_undo_idna(ls, q, ls, sizeof(ls));
- if (w < 0)
- return w;
- if (w > 0)
- q = w;
+ if (q > 0) {
+ w = dns_label_undo_idna(ls, q, ls, sizeof(ls));
+ if (w < 0)
+ return w;
+ if (w > 0)
+ q = w;
+ }
if (r == 0 && q == 0)
return true;
@@ -605,11 +650,13 @@ int dns_name_change_suffix(const char *name, const char *old_suffix, const char
r = dns_label_unescape(&n, ln, sizeof(ln));
if (r < 0)
return r;
- k = dns_label_undo_idna(ln, r, ln, sizeof(ln));
- if (k < 0)
- return k;
- if (k > 0)
- r = k;
+ if (r > 0) {
+ k = dns_label_undo_idna(ln, r, ln, sizeof(ln));
+ if (k < 0)
+ return k;
+ if (k > 0)
+ r = k;
+ }
if (!saved_after)
saved_after = n;
@@ -617,11 +664,13 @@ int dns_name_change_suffix(const char *name, const char *old_suffix, const char
q = dns_label_unescape(&s, ls, sizeof(ls));
if (q < 0)
return q;
- w = dns_label_undo_idna(ls, q, ls, sizeof(ls));
- if (w < 0)
- return w;
- if (w > 0)
- q = w;
+ if (q > 0) {
+ w = dns_label_undo_idna(ls, q, ls, sizeof(ls));
+ if (w < 0)
+ return w;
+ if (w > 0)
+ q = w;
+ }
if (r == 0 && q == 0)
break;
diff --git a/src/shared/dns-domain.h b/src/shared/dns-domain.h
index 99c72574db..c68f1945e1 100644
--- a/src/shared/dns-domain.h
+++ b/src/shared/dns-domain.h
@@ -25,7 +25,10 @@
#include "hashmap.h"
#include "in-addr-util.h"
+/* Length of a single label, with all escaping removed, excluding any trailing dot or NUL byte */
#define DNS_LABEL_MAX 63
+
+/* Worst case length of a single label, with all escaping applied and room for a trailing NUL byte. */
#define DNS_LABEL_ESCAPED_MAX (DNS_LABEL_MAX*4+1)
int dns_label_unescape(const char **name, char *dest, size_t sz);
diff --git a/src/test/test-dns-domain.c b/src/test/test-dns-domain.c
index f010e4e19a..7ad59d378a 100644
--- a/src/test/test-dns-domain.c
+++ b/src/test/test-dns-domain.c
@@ -136,7 +136,7 @@ static void test_dns_label_escape_one(const char *what, size_t l, const char *ex
}
static void test_dns_label_escape(void) {
- test_dns_label_escape_one("", 0, "", 0);
+ test_dns_label_escape_one("", 0, NULL, -EINVAL);
test_dns_label_escape_one("hallo", 5, "hallo", 5);
test_dns_label_escape_one("hallo", 6, NULL, -EINVAL);
test_dns_label_escape_one("hallo hallo.foobar,waldi", 24, "hallo\\032hallo\\.foobar\\044waldi", 31);
generated by cgit v1.2.3-54-g00ecf (git 2.45.2) at 2025-10-25 11:33:11 +0000