lib/glibc
1
0
Fork 0
mirror of https://sourceware.org/git/glibc.git synced 2025-07-29 11:41:21 +03:00
Code Activity

resolv: Reduce EDNS payload size to 1200 bytes [BZ #21361]

Browse Source 
This hardens the stub resolver against fragmentation-based attacks.
This commit is contained in:
Florian Weimer
2017-04-13 13:09:38 +02:00
parent c803cb9b24
commit e14a27723c
10 changed files with 651 additions and 13 deletions
Download Patch File Download Diff File Expand all files Collapse all files

23
resolv/res_query.c
View File

@ -78,6 +78,7 @@
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <resolv/resolv-internal.h>
/* Options. Leave them on. */
/* #undef DEBUG */
@ -147,7 +148,10 @@ __libc_res_nquery(res_state statp,
if ((oflags & RES_F_EDNS0ERR) == 0
&& (statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC)) != 0)
{
n = __res_nopt(statp, n, query1, bufsize, anslen / 2);
/* Use RESOLV_EDNS_BUFFER_SIZE because the receive
buffer can be reallocated. */
n = __res_nopt (statp, n, query1, bufsize,
RESOLV_EDNS_BUFFER_SIZE);
if (n < 0)
goto unspec_nomem;
}
@ -168,8 +172,10 @@ __libc_res_nquery(res_state statp,
if (n > 0
&& (oflags & RES_F_EDNS0ERR) == 0
&& (statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC)) != 0)
n = __res_nopt(statp, n, query2, bufsize - nused - n,
anslen / 2);
/* Use RESOLV_EDNS_BUFFER_SIZE because the receive
buffer can be reallocated. */
n = __res_nopt (statp, n, query2, bufsize,
RESOLV_EDNS_BUFFER_SIZE);
nquery2 = n;
}
@ -183,7 +189,16 @@ __libc_res_nquery(res_state statp,
if (n > 0
&& (oflags & RES_F_EDNS0ERR) == 0
&& (statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC)) != 0)
n = __res_nopt(statp, n, query1, bufsize, anslen);
{
/* Use RESOLV_EDNS_BUFFER_SIZE if the receive buffer
can be reallocated. */
size_t advertise;
if (answerp == NULL)
advertise = anslen;
else
advertise = RESOLV_EDNS_BUFFER_SIZE;
n = __res_nopt (statp, n, query1, bufsize, advertise);
}
nquery1 = n;
}