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Fix mg_dns_parse_name_depth()

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This commit is contained in:
Sergey Lyubka 2022-03-21 16:29:27 +00:00
parent bf025537b6
commit 1bc81df00e
3 changed files with 26 additions and 19 deletions
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20
mongoose.c
View File

@ -143,10 +143,12 @@ void mg_resolve_cancel(struct mg_connection *c) {
}
static size_t mg_dns_parse_name_depth(const uint8_t *s, size_t len, size_t ofs,
char *to, size_t tolen, int depth) {
size_t i = 0, j = 0;
if (tolen > 0) to[0] = '\0';
char *to, size_t tolen, size_t j,
int depth) {
size_t i = 0;
if (tolen > 0 && depth == 0) to[0] = '\0';
if (depth > 5) return 0;
// MG_INFO(("ofs %lx %x %x", (unsigned long) ofs, s[ofs], s[ofs + 1]));
while (ofs + i + 1 < len) {
size_t n = s[ofs + i];
if (n == 0) {
@ -155,9 +157,9 @@ static size_t mg_dns_parse_name_depth(const uint8_t *s, size_t len, size_t ofs,
}
if (n & 0xc0) {
size_t ptr = (((n & 0x3f) << 8) | s[ofs + i + 1]); // 12 is hdr len
// MG_INFO(("PTR %lu", (unsigned long) ptr));
// MG_INFO(("PTR %lx", (unsigned long) ptr));
if (ptr + 1 < len && (s[ptr] & 0xc0) == 0 &&
mg_dns_parse_name_depth(s, len, ptr, to, tolen, depth + 1) == 0)
mg_dns_parse_name_depth(s, len, ptr, to, tolen, j, depth + 1) == 0)
return 0;
i += 2;
break;
@ -171,6 +173,7 @@ static size_t mg_dns_parse_name_depth(const uint8_t *s, size_t len, size_t ofs,
j += n;
i += n + 1;
if (j < tolen) to[j] = '\0'; // Zero-terminate this chunk
// MG_INFO(("--> [%s]", to));
}
if (tolen > 0) to[tolen - 1] = '\0'; // Make sure make sure it is nul-term
return i;
@ -178,7 +181,7 @@ static size_t mg_dns_parse_name_depth(const uint8_t *s, size_t len, size_t ofs,
static size_t mg_dns_parse_name(const uint8_t *s, size_t n, size_t ofs,
char *dst, size_t dstlen) {
return mg_dns_parse_name_depth(s, n, ofs, dst, dstlen, 0);
return mg_dns_parse_name_depth(s, n, ofs, dst, dstlen, 0, 0);
}
size_t mg_dns_parse_rr(const uint8_t *buf, size_t len, size_t ofs,
@ -218,12 +221,13 @@ bool mg_dns_parse(const uint8_t *buf, size_t len, struct mg_dns_message *dm) {
for (i = 0; i < mg_ntohs(h->num_questions); i++) {
if ((n = mg_dns_parse_rr(buf, len, ofs, true, &rr)) == 0) return false;
// MG_INFO(("Q %zu %zu", ofs, n));
// MG_INFO(("Q %lu %lu %hu/%hu", ofs, n, rr.atype, rr.aclass));
ofs += n;
}
for (i = 0; i < mg_ntohs(h->num_answers); i++) {
// MG_INFO(("A -- %zu %zu %s", ofs, n, dm->name));
if ((n = mg_dns_parse_rr(buf, len, ofs, false, &rr)) == 0) return false;
// MG_INFO(("A -- %lu %lu %hu/%hu %s", ofs, n, rr.atype, rr.aclass,
// dm->name));
mg_dns_parse_name(buf, len, ofs, dm->name, sizeof(dm->name));
ofs += n;

20
src/dns.c
View File

@ -31,10 +31,12 @@ void mg_resolve_cancel(struct mg_connection *c) {
}
static size_t mg_dns_parse_name_depth(const uint8_t *s, size_t len, size_t ofs,
char *to, size_t tolen, int depth) {
size_t i = 0, j = 0;
if (tolen > 0) to[0] = '\0';
char *to, size_t tolen, size_t j,
int depth) {
size_t i = 0;
if (tolen > 0 && depth == 0) to[0] = '\0';
if (depth > 5) return 0;
// MG_INFO(("ofs %lx %x %x", (unsigned long) ofs, s[ofs], s[ofs + 1]));
while (ofs + i + 1 < len) {
size_t n = s[ofs + i];
if (n == 0) {
@ -43,9 +45,9 @@ static size_t mg_dns_parse_name_depth(const uint8_t *s, size_t len, size_t ofs,
}
if (n & 0xc0) {
size_t ptr = (((n & 0x3f) << 8) | s[ofs + i + 1]); // 12 is hdr len
// MG_INFO(("PTR %lu", (unsigned long) ptr));
// MG_INFO(("PTR %lx", (unsigned long) ptr));
if (ptr + 1 < len && (s[ptr] & 0xc0) == 0 &&
mg_dns_parse_name_depth(s, len, ptr, to, tolen, depth + 1) == 0)
mg_dns_parse_name_depth(s, len, ptr, to, tolen, j, depth + 1) == 0)
return 0;
i += 2;
break;
@ -59,6 +61,7 @@ static size_t mg_dns_parse_name_depth(const uint8_t *s, size_t len, size_t ofs,
j += n;
i += n + 1;
if (j < tolen) to[j] = '\0'; // Zero-terminate this chunk
// MG_INFO(("--> [%s]", to));
}
if (tolen > 0) to[tolen - 1] = '\0'; // Make sure make sure it is nul-term
return i;
@ -66,7 +69,7 @@ static size_t mg_dns_parse_name_depth(const uint8_t *s, size_t len, size_t ofs,
static size_t mg_dns_parse_name(const uint8_t *s, size_t n, size_t ofs,
char *dst, size_t dstlen) {
return mg_dns_parse_name_depth(s, n, ofs, dst, dstlen, 0);
return mg_dns_parse_name_depth(s, n, ofs, dst, dstlen, 0, 0);
}
size_t mg_dns_parse_rr(const uint8_t *buf, size_t len, size_t ofs,
@ -106,12 +109,13 @@ bool mg_dns_parse(const uint8_t *buf, size_t len, struct mg_dns_message *dm) {
for (i = 0; i < mg_ntohs(h->num_questions); i++) {
if ((n = mg_dns_parse_rr(buf, len, ofs, true, &rr)) == 0) return false;
// MG_INFO(("Q %zu %zu", ofs, n));
// MG_INFO(("Q %lu %lu %hu/%hu", ofs, n, rr.atype, rr.aclass));
ofs += n;
}
for (i = 0; i < mg_ntohs(h->num_answers); i++) {
// MG_INFO(("A -- %zu %zu %s", ofs, n, dm->name));
if ((n = mg_dns_parse_rr(buf, len, ofs, false, &rr)) == 0) return false;
// MG_INFO(("A -- %lu %lu %hu/%hu %s", ofs, n, rr.atype, rr.aclass,
// dm->name));
mg_dns_parse_name(buf, len, ofs, dm->name, sizeof(dm->name));
ofs += n;

5
test/unit_test.c
View File

@ -1342,10 +1342,9 @@ static void test_dns(void) {
0x00, 0x04, 0x57, 0xf8, 0x64, 0xd8, 0xc0, 0x45, 0x00, 0x01, 0x00,
0x01, 0x00, 0x00, 0x00, 0x0a, 0x00, 0x04, 0x57, 0xf8, 0x64, 0xd7,
};
MG_INFO(("--------------"));
ASSERT(mg_dns_parse(d, sizeof(d), &dm) == 1);
MG_INFO(("[%s]", dm.name));
ASSERT(strcmp(dm.name, "com") == 0); // TODO(lsm): fix this
// MG_INFO(("[%s]", dm.name));
ASSERT(strcmp(dm.name, "new-fp-shed.wg1.b.yahoo.com") == 0);
}
test_dns_timeout("udp://127.0.0.1:12345", "DNS timeout");