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tcp: "TCP" hash secret doesn't need to be TCP specific

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The TCP state structure includes a 128-bit hash_secret which we use for
SipHash calculations to mitigate attacks on the TCP hash table and initial
sequence number.

We have plans to use SipHash in places that aren't TCP related, and there's
no particular reason they'd need their own secret.  So move the hash_secret
to the general context structure.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This commit is contained in:
David Gibson 2023-11-30 13:02:21 +11:00 • committed by Stefano Brivio
parent cf83988e96
commit e21b6d69b1
4 changed files with 44 additions and 35 deletions

40
passt.c
View file

@ -35,6 +35,9 @@
#include <syslog.h>
#include <sys/prctl.h>
#include <netinet/if_ether.h>
#ifdef HAS_GETRANDOM
#include <sys/random.h>
#endif
#include "util.h"
#include "passt.h"
@ -103,6 +106,41 @@ static void post_handler(struct ctx *c, const struct timespec *now)
#undef CALL_PROTO_HANDLER
}
/**
* secret_init() - Create secret value for SipHash calculations
* @c: Execution context
*/
static void secret_init(struct ctx *c)
{
#ifndef HAS_GETRANDOM
int dev_random = open("/dev/random", O_RDONLY);
unsigned int random_read = 0;
while (dev_random && random_read < sizeof(c->hash_secret)) {
int ret = read(dev_random,
(uint8_t *)&c->hash_secret + random_read,
sizeof(c->hash_secret) - random_read);
if (ret == -1 && errno == EINTR)
continue;
if (ret <= 0)
break;
random_read += ret;
}
if (dev_random >= 0)
close(dev_random);
if (random_read < sizeof(c->hash_secret)) {
#else
if (getrandom(&c->hash_secret, sizeof(c->hash_secret),
GRND_RANDOM) < 0) {
#endif /* !HAS_GETRANDOM */
perror("TCP initial sequence getrandom");
exit(EXIT_FAILURE);
}
}
/**
* timer_init() - Set initial timestamp for timer runs to current time
* @c: Execution context
@ -237,6 +275,8 @@ int main(int argc, char **argv)
tap_sock_init(&c);
secret_init(&c);
clock_gettime(CLOCK_MONOTONIC, &now);
if ((!c.no_udp && udp_init(&c)) || (!c.no_tcp && tcp_init(&c)))