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cc3a67760c
NBT has a funny thing where it sometimes needs to send a trailing dot as
part of the last component, because the string representation is a user
name. In DNS, "example.com", and "example.com." are the same, both
having three components ("example", "com", ""); in NBT, we want to treat
them differently, with the second form having the three components
("example", "com.", "").
This retains the logic of e6e2ec0001.
Also DNS compression cannot be turned off for NBT.
BUG: https://bugzilla.samba.org/show_bug.cgi?id=14378
Signed-off-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
135 lines
3.5 KiB
C
135 lines
3.5 KiB
C
#include "includes.h"
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#include "../librpc/ndr/libndr.h"
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#include "ndr_dns_utils.h"
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/**
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push a dns/nbt string list to the wire
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*/
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enum ndr_err_code ndr_push_dns_string_list(struct ndr_push *ndr,
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struct ndr_token_list *string_list,
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int ndr_flags,
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const char *s,
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bool is_nbt)
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{
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const char *start = s;
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bool use_compression;
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size_t max_length;
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if (is_nbt) {
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use_compression = true;
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/*
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* Max length is longer in NBT/Wins, because Windows counts
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* the semi-decompressed size of the netbios name (16 bytes)
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* rather than the wire size of 32, which is what you'd expect
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* if it followed RFC1002 (it uses the short form in
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* [MS-WINSRA]). In other words the maximum size of the
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* "scope" is 237, not 221.
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*
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* We make the size limit slightly larger than 255 + 16,
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* because the 237 scope limit is already enforced in the
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* winsserver code with a specific return value; bailing out
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* here would muck with that.
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*/
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max_length = 274;
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} else {
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use_compression = !(ndr->flags & LIBNDR_FLAG_NO_COMPRESSION);
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max_length = 255;
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}
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if (!(ndr_flags & NDR_SCALARS)) {
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return NDR_ERR_SUCCESS;
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}
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while (s && *s) {
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enum ndr_err_code ndr_err;
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char *compname;
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size_t complen;
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uint32_t offset;
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if (use_compression) {
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/* see if we have pushed the remaining string already,
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* if so we use a label pointer to this string
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*/
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ndr_err = ndr_token_retrieve_cmp_fn(string_list, s,
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&offset,
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(comparison_fn_t)strcmp,
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false);
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if (NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
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uint8_t b[2];
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if (offset > 0x3FFF) {
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return ndr_push_error(ndr, NDR_ERR_STRING,
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"offset for dns string " \
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"label pointer " \
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"%u[%08X] > 0x00003FFF",
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offset, offset);
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}
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b[0] = 0xC0 | (offset>>8);
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b[1] = (offset & 0xFF);
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return ndr_push_bytes(ndr, b, 2);
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}
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}
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complen = strcspn(s, ".");
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/* the length must fit into 6 bits (i.e. <= 63) */
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if (complen > 0x3F) {
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return ndr_push_error(ndr, NDR_ERR_STRING,
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"component length %u[%08X] > " \
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"0x0000003F",
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(unsigned)complen,
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(unsigned)complen);
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}
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if (complen == 0 && s[complen] == '.') {
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return ndr_push_error(ndr, NDR_ERR_STRING,
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"component length is 0 "
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"(consecutive dots)");
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}
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if (is_nbt && s[complen] == '.' && s[complen + 1] == '\0') {
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/* nbt names are sometimes usernames, and we need to
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* keep a trailing dot to ensure it is byte-identical,
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* (not just semantically identical given DNS
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* semantics). */
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complen++;
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}
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compname = talloc_asprintf(ndr, "%c%*.*s",
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(unsigned char)complen,
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(unsigned char)complen,
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(unsigned char)complen, s);
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NDR_ERR_HAVE_NO_MEMORY(compname);
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/* remember the current component + the rest of the string
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* so it can be reused later
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*/
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if (use_compression) {
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NDR_CHECK(ndr_token_store(ndr, string_list, s,
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ndr->offset));
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}
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/* push just this component into the blob */
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NDR_CHECK(ndr_push_bytes(ndr, (const uint8_t *)compname,
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complen+1));
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talloc_free(compname);
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s += complen;
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if (*s == '.') {
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s++;
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}
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if (s - start > max_length) {
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return ndr_push_error(ndr, NDR_ERR_STRING,
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"name > %zu character long",
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max_length);
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}
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}
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/* if we reach the end of the string and have pushed the last component
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* without using a label pointer, we need to terminate the string
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*/
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return ndr_push_bytes(ndr, (const uint8_t *)"", 1);
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}
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