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dns: introduce dns_name_from_wire_format

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This is implemented in various places, but it is better to share this
code.
This commit is contained in:
Ronan Pigott
2024-09-13 22:57:50 -07:00
parent 00f546e25e
commit 427166c3b0
3 changed files with 159 additions and 0 deletions
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src/shared/dns-domain.c
+69
View File
@@ -898,6 +898,75 @@ int dns_name_to_wire_format(const char *domain, uint8_t *buffer, size_t len, boo
return out - buffer;
}
/* Decode a domain name according to RFC 1035 Section 3.1, without compression */
int dns_name_from_wire_format(const uint8_t **data, size_t *len, char **ret) {
_cleanup_free_ char *domain = NULL;
const uint8_t *optval;
size_t optlen, n = 0;
int r;
assert(data);
assert(len);
assert(*data || *len == 0);
assert(ret);
optval = *data;
optlen = *len;
for (;;) {
const char *label;
uint8_t c;
/* Unterminated name */
if (optlen == 0)
return -EBADMSG;
/* RFC 1035 § 3.1 total length of encoded name is limited to 255 octets */
if (*len - optlen > 255)
return -EMSGSIZE;
c = *optval;
optval++;
optlen--;
if (c == 0)
/* End label */
break;
if (c > DNS_LABEL_MAX)
return -EBADMSG;
if (c > optlen)
return -EMSGSIZE;
/* Literal label */
label = (const char*) optval;
optval += c;
optlen -= c;
if (!GREEDY_REALLOC(domain, n + (n != 0) + DNS_LABEL_ESCAPED_MAX))
return -ENOMEM;
if (n != 0)
domain[n++] = '.';
r = dns_label_escape(label, c, domain + n, DNS_LABEL_ESCAPED_MAX);
if (r < 0)
return r;
n += r;
}
if (!GREEDY_REALLOC(domain, n + 1))
return -ENOMEM;
domain[n] = '\0';
*ret = TAKE_PTR(domain);
*data = optval;
*len = optlen;
return n;
}
static bool srv_type_label_is_valid(const char *label, size_t n) {
assert(label);
src/shared/dns-domain.h
+1
View File
@@ -79,6 +79,7 @@ bool dns_name_is_root(const char *name);
bool dns_name_is_single_label(const char *name);
int dns_name_to_wire_format(const char *domain, uint8_t *buffer, size_t len, bool canonical);
int dns_name_from_wire_format(const uint8_t **data, size_t *len, char **ret);
bool dns_srv_type_is_valid(const char *name);
bool dnssd_srv_type_is_valid(const char *name);
src/test/test-dns-domain.c
+89
View File
@@ -119,6 +119,95 @@ TEST(dns_name_to_wire_format) {
test_dns_name_to_wire_format_one("a12345678.a12345678.a12345678.a12345678.a12345678.a12345678.a12345678.a12345678.a12345678.a12345678.a12345678.a12345678.a12345678.a12345678.a12345678.a12345678.a12345678.a12345678.a12345678.a12345678.a12345678.a12345678.a12345678.a12345678.a12345678.a12", out4, sizeof(out4), sizeof(out4));
}
static void test_dns_name_from_wire_format_one(const char *expect, const uint8_t *what, size_t len, int ret) {
_cleanup_free_ char *name = NULL;
int r;
log_info("%s, %s, %zu, →%d", what, strnull(expect), len, ret);
r = dns_name_from_wire_format(&what, &len, &name);
assert_se(r == ret);
if (r >= 0) {
assert(expect); /* for gcc */
assert_se(memcmp(name, expect, r) == 0);
}
}
TEST(dns_name_from_wire_format) {
static const uint8_t in0[] = { 0 };
static const uint8_t in1[] = { 3, 'f', 'o', 'o', 0 };
static const uint8_t in2[] = { 5, 'h', 'a', 'l', 'l', 'o', 3, 'f', 'o', 'o', 3, 'b', 'a', 'r', 0 };
static const uint8_t in2_1[] = { 5, 'h', 'a', 'l', 'l', 'o', 3, 'f', 'o', 'o', 0, 'b', 'a', 'r', 0 };
static const uint8_t in3[] = { 4, ' ', 'f', 'o', 'o', 3, 'b', 'a', 'r', 0 };
static const uint8_t in4[] = { 9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
3, 'a', '1', '2', 0 }; /* 255 octets */
static const uint8_t in5[] = { 9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
9, 'a', '1', '2', '3', '4', '5', '6', '7', '8',
3, 'a', '1', '2', 0 }; /* 265 octets */
test_dns_name_from_wire_format_one("", in0, sizeof(in0), strlen(""));
test_dns_name_from_wire_format_one("foo", in1, sizeof(in1), strlen("foo"));
test_dns_name_from_wire_format_one(NULL, in1, sizeof(in1) - 1, -EBADMSG);
test_dns_name_from_wire_format_one("hallo.foo.bar", in2, sizeof(in2), strlen("hallo.foo.bar"));
test_dns_name_from_wire_format_one("hallo.foo", in2_1, sizeof(in2_1), strlen("hallo.foo"));
test_dns_name_from_wire_format_one("\\032foo.bar", in3, sizeof(in3), strlen("\\032foo.bar"));
test_dns_name_from_wire_format_one(NULL, in5, sizeof(in5), -EMSGSIZE);
test_dns_name_from_wire_format_one("a12345678.a12345678.a12345678.a12345678.a12345678.a12345678.a12345678.a12345678.a12345678.a12345678.a12345678.a12345678.a12345678.a12345678.a12345678.a12345678.a12345678.a12345678.a12345678.a12345678.a12345678.a12345678.a12345678.a12345678.a12345678.a12", in4, sizeof(in4), 253);
}
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;