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dns-domain: be more strict when encoding/decoding labels
Labels of zero length are not OK, refuse them early on. The concept of a "zero-length label" doesn't exist, a zero-length full domain name however does (representing the root domain). See RFC 2181, Section 11.
This commit is contained in:
Lennart Poettering
parent
bca27e1729
commit
3b37fa7352
@ -185,7 +185,11 @@ int dns_label_unescape_suffix(const char *name, const char **label_terminal, cha
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int dns_label_escape(const char *p, size_t l, char *dest, size_t sz) {
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char *q;
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if (l > DNS_LABEL_MAX)
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/* DNS labels must be between 1 and 63 characters long. A
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* zero-length label does not exist. See RFC 2182, Section
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* 11. */
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if (l <= 0 || l > DNS_LABEL_MAX)
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return -EINVAL;
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if (sz < 1)
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return -ENOSPC;
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@ -198,10 +202,11 @@ int dns_label_escape(const char *p, size_t l, char *dest, size_t sz) {
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if (*p == '.' || *p == '\\') {
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/* Dot or backslash */
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if (sz < 3)
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return -ENOSPC;
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/* Dot or backslash */
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*(q++) = '\\';
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*(q++) = *p;
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@ -253,7 +258,7 @@ int dns_label_escape_new(const char *p, size_t l, char **ret) {
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assert(p);
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assert(ret);
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if (l > DNS_LABEL_MAX)
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if (l <= 0 || l > DNS_LABEL_MAX)
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return -EINVAL;
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s = new(char, DNS_LABEL_ESCAPED_MAX);
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@ -273,32 +278,52 @@ int dns_label_escape_new(const char *p, size_t l, char **ret) {
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int dns_label_apply_idna(const char *encoded, size_t encoded_size, char *decoded, size_t decoded_max) {
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#ifdef HAVE_LIBIDN
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_cleanup_free_ uint32_t *input = NULL;
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size_t input_size;
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size_t input_size, l;
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const char *p;
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bool contains_8bit = false;
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char buffer[DNS_LABEL_MAX+1];
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assert(encoded);
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assert(decoded);
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assert(decoded_max >= DNS_LABEL_MAX);
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/* Converts an U-label into an A-label */
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if (encoded_size <= 0)
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return 0;
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return -EINVAL;
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for (p = encoded; p < encoded + encoded_size; p++)
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if ((uint8_t) *p > 127)
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contains_8bit = true;
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if (!contains_8bit)
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if (!contains_8bit) {
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if (encoded_size > DNS_LABEL_MAX)
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return -EINVAL;
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return 0;
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}
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input = stringprep_utf8_to_ucs4(encoded, encoded_size, &input_size);
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if (!input)
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return -ENOMEM;
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if (idna_to_ascii_4i(input, input_size, decoded, 0) != 0)
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if (idna_to_ascii_4i(input, input_size, buffer, 0) != 0)
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return -EINVAL;
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return strlen(decoded);
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l = strlen(buffer);
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/* Verify that the the result is not longer than one DNS label. */
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if (l <= 0 || l > DNS_LABEL_MAX)
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return -EINVAL;
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if (l > decoded_max)
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return -ENOSPC;
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memcpy(decoded, buffer, l);
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/* If there's room, append a trailing NUL byte, but only then */
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if (decoded_max > l)
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decoded[l] = 0;
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return (int) l;
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#else
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return 0;
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#endif
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@ -312,11 +337,14 @@ int dns_label_undo_idna(const char *encoded, size_t encoded_size, char *decoded,
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uint32_t *output = NULL;
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size_t w;
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/* To be invoked after unescaping */
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/* To be invoked after unescaping. Converts an A-label into an U-label. */
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assert(encoded);
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assert(decoded);
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if (encoded_size <= 0 || encoded_size > DNS_LABEL_MAX)
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return -EINVAL;
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if (encoded_size < sizeof(IDNA_ACE_PREFIX)-1)
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return 0;
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@ -336,11 +364,16 @@ int dns_label_undo_idna(const char *encoded, size_t encoded_size, char *decoded,
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if (!result)
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return -ENOMEM;
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if (w <= 0)
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return 0;
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if (w+1 > decoded_max)
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return -EINVAL;
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if (w > decoded_max)
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return -ENOSPC;
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memcpy(decoded, result, w);
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/* Append trailing NUL byte if there's space, but only then. */
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if (decoded_max > w)
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decoded[w] = 0;
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memcpy(decoded, result, w+1);
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return w;
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#else
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return 0;
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@ -511,24 +544,32 @@ int dns_name_equal(const char *x, const char *y) {
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r = dns_label_unescape(&x, la, sizeof(la));
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if (r < 0)
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return r;
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if (r > 0) {
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k = dns_label_undo_idna(la, r, la, sizeof(la));
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if (k < 0)
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return k;
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if (k > 0)
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r = k;
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}
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q = dns_label_unescape(&y, lb, sizeof(lb));
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if (q < 0)
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return q;
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if (q > 0) {
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w = dns_label_undo_idna(lb, q, lb, sizeof(lb));
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if (w < 0)
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return w;
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if (w > 0)
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q = w;
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}
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/* If one name had fewer labels than the other, this
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* will show up as empty label here, which the
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* strcasecmp() below will properly consider different
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* from a non-empty label. */
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la[r] = lb[q] = 0;
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if (strcasecmp(la, lb))
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if (strcasecmp(la, lb) != 0)
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return false;
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}
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}
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@ -549,11 +590,13 @@ int dns_name_endswith(const char *name, const char *suffix) {
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r = dns_label_unescape(&n, ln, sizeof(ln));
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if (r < 0)
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return r;
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if (r > 0) {
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k = dns_label_undo_idna(ln, r, ln, sizeof(ln));
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if (k < 0)
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return k;
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if (k > 0)
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r = k;
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}
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if (!saved_n)
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saved_n = n;
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@ -561,11 +604,13 @@ int dns_name_endswith(const char *name, const char *suffix) {
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q = dns_label_unescape(&s, ls, sizeof(ls));
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if (q < 0)
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return q;
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if (q > 0) {
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w = dns_label_undo_idna(ls, q, ls, sizeof(ls));
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if (w < 0)
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return w;
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if (w > 0)
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q = w;
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}
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if (r == 0 && q == 0)
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return true;
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@ -605,11 +650,13 @@ int dns_name_change_suffix(const char *name, const char *old_suffix, const char
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r = dns_label_unescape(&n, ln, sizeof(ln));
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if (r < 0)
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return r;
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if (r > 0) {
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k = dns_label_undo_idna(ln, r, ln, sizeof(ln));
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if (k < 0)
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return k;
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if (k > 0)
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r = k;
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}
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if (!saved_after)
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saved_after = n;
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@ -617,11 +664,13 @@ int dns_name_change_suffix(const char *name, const char *old_suffix, const char
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q = dns_label_unescape(&s, ls, sizeof(ls));
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if (q < 0)
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return q;
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if (q > 0) {
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w = dns_label_undo_idna(ls, q, ls, sizeof(ls));
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if (w < 0)
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return w;
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if (w > 0)
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q = w;
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}
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if (r == 0 && q == 0)
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break;
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@ -25,7 +25,10 @@
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#include "hashmap.h"
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#include "in-addr-util.h"
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/* Length of a single label, with all escaping removed, excluding any trailing dot or NUL byte */
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#define DNS_LABEL_MAX 63
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/* Worst case length of a single label, with all escaping applied and room for a trailing NUL byte. */
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#define DNS_LABEL_ESCAPED_MAX (DNS_LABEL_MAX*4+1)
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int dns_label_unescape(const char **name, char *dest, size_t sz);
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@ -136,7 +136,7 @@ static void test_dns_label_escape_one(const char *what, size_t l, const char *ex
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}
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static void test_dns_label_escape(void) {
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test_dns_label_escape_one("", 0, "", 0);
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test_dns_label_escape_one("", 0, NULL, -EINVAL);
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test_dns_label_escape_one("hallo", 5, "hallo", 5);
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test_dns_label_escape_one("hallo", 6, NULL, -EINVAL);
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test_dns_label_escape_one("hallo hallo.foobar,waldi", 24, "hallo\\032hallo\\.foobar\\044waldi", 31);
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