upstream/bind9
1
0
Fork 0
mirror of https://github.com/isc-projects/bind9.git synced 2026-06-11 10:50:00 -04:00
Code Issues Projects Releases Packages Wiki Activity Actions 2

Remove a redundant variable-length array

Browse source 
In the GSS-TSIG verification code there was an alarming
variable-length array whose size came off the network, from the
signature in the request. It turned out to be safe, because the caller
had previously checked that the signature had a reasonable size.
However, the safety checks are in the generic TSIG implementation, and
the risky VLA usage was in the GSS-specific code, and they are
separated by the DST indirection layer, so it wasn't immediately
obvious that the risky VLA was in fact safe.

In fact this risky VLA was completely unnecessary, because the GSS
signature can be verified in place without being copied to the stack,
like the message covered by the signature. The `REGION_TO_GBUFFER()`
macro backwardly assigns the region in its left argument to the GSS
buffer in its right argument; this is just a pointer and length
conversion, without copying any data. The `gss_verify_mic()` call uses
both message and signature GSS buffers in a read-only manner.

(cherry picked from commit eeead1cfe7)
This commit is contained in:
Tony Finch 2022-03-10 13:04:08 +00:00
parent 312bdb9e5c
commit ac5d61541d
1 changed files with 2 additions and 7 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

9
lib/dns/gssapi_link.c
View file

@ -189,11 +189,10 @@ gssapi_sign(dst_context_t *dctx, isc_buffer_t *sig) {
static isc_result_t
gssapi_verify(dst_context_t *dctx, const isc_region_t *sig) {
dst_gssapi_signverifyctx_t *ctx = dctx->ctxdata.gssctx;
isc_region_t message, r;
isc_region_t message;
gss_buffer_desc gmessage, gsig;
OM_uint32 minor, gret;
gss_ctx_id_t gssctx = dctx->key->keydata.gssctx;
unsigned char buf[sig->length];
char err[1024];
/*
@ -202,11 +201,7 @@ gssapi_verify(dst_context_t *dctx, const isc_region_t *sig) {
*/
isc_buffer_usedregion(ctx->buffer, &message);
REGION_TO_GBUFFER(message, gmessage);
memmove(buf, sig->base, sig->length);
r.base = buf;
r.length = sig->length;
REGION_TO_GBUFFER(r, gsig);
REGION_TO_GBUFFER(*sig, gsig);
/*
* Verify the data.