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Use random, not progressive TXID for DNS requests

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This commit is contained in:
dmiller 2026-08-14 19:04:39 +00:00
parent 52b1553633
commit 5650f35c6d
3 changed files with 50 additions and 6 deletions
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8
libnetutil/massdns.cc
View file

@ -622,10 +622,6 @@ DNS::Stats DNS::Resolver::getStats() const
return impl->stat;
}
//------------------- Globals ---------------------
u16 DNS::Factory::progressiveId = get_random_u16();
//------------------- Prototypes and macros ---------------------
#define ACTION_FINISHED 0
@ -693,7 +689,7 @@ void DNS::ResolverImpl::add_request(DNS::Request &reqt)
tpreq->tries = 0;
tpreq->servers_tried = 0;
tpreq->alt_req = false;
tpreq->id = DNS::Factory::progressiveId++;
tpreq->id = get_random_unique_u16();
new_reqs.push_back(tpreq);
stat.actual++;
@ -711,7 +707,7 @@ void DNS::ResolverImpl::add_request(DNS::Request &reqt)
*tpreq_alt = *tpreq;
tpreq_alt->targ = req_aaaa;
tpreq_alt->alt_req = true;
tpreq_alt->id = DNS::Factory::progressiveId++;
tpreq_alt->id = get_random_unique_u16();
new_reqs.push_back(tpreq_alt);
stat.actual++;
}

1
nbase/nbase.h
View file

@ -521,6 +521,7 @@ u32 get_random_u32();
u16 get_random_u16();
u8 get_random_u8();
u32 get_random_unique_u32();
u16 get_random_unique_u16();
/* Create a new socket inheritable by subprocesses. On non-Windows systems it's
just a normal socket. */

47
nbase/nbase_rnd.c
View file

@ -359,3 +359,50 @@ u32 get_random_unique_u32() {
return output;
}
/* The same, but for 16-bit numbers */
u16 get_random_unique_u16() {
static u16 state, tweak1, tweak2, tweak3;
static int state_init = 0;
u16 output;
/* Initialize if we need to */
if (!state_init) {
get_random_bytes(&state, sizeof(state));
get_random_bytes(&tweak1, sizeof(tweak1));
get_random_bytes(&tweak2, sizeof(tweak2));
get_random_bytes(&tweak3, sizeof(tweak3));
state_init = 1;
}
/* https://oeis.org/A383940
*/
state = (((state * 25173) & 0xFFFF) + 13849) & 0xFFFF;
output = state;
/* Then rotate and XOR */
output = ((output << 7) | (output >> (16 - 7)));
output = output ^ tweak1; /* This is the round key */
/* End round 1, start round 2 */
/* Then put it through an affine transform */
output = (((output * 4321) & 0xFFFF) + 12345) & 0xFFFF;
/* Then rotate and XOR some more */
output = ((output << 11) | (output >> (16 - 11)));
output = output ^ tweak2;
/* End round 2, start round 3 */
/* Then put it through another affine transform (Quick C/C++ constants) */
output = (((output * 31337) & 0xFFFF) + 1997) & 0xFFFF;
/* Then rotate and XOR some more */
output = ((output << 5) | (output >> (16 - 5)));
output = output ^ tweak3;
return output;
}