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Pad queries when EDNS0 is enabled.

Browse source 
Behavior is compliant with
https://tools.ietf.org/html/draft-ietf-dprive-padding-policy-04

EDNS0 is only enabled when the netcontext requests it, i.e. in DNS-over-TLS
mode.

Bug: 69623036
Bug: 64133961
Test: Wireshark verified. Integration tests echo padding and pass.
Merged-In: Ie5439b0ad505ebf393a83c87845fd02549afc4a2
Merged-In: I274d659782870818274526d23d3a3c4640cad92d
Change-Id: I5ef600e02a572d281441e890cc981614f150629b
(cherry picked from commit 23e4081009bb58d9c09e615186208b77749e72de)
This commit is contained in:
Ben Schwartz 2018-02-05 17:54:06 -05:00 committed by Erik Kline
parent d65576d406
commit 622a36923e
3 changed files with 25 additions and 0 deletions
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4
libc/dns/include/resolv_params.h
View file

@ -34,6 +34,10 @@
* servers.
*/
/* If EDNS0_PADDING is defined, queries will be padded to a multiple of this length
when EDNS0 is active. */
#define EDNS0_PADDING 128
/* per-netid configuration parameters passed from netd to the resolver */
struct __res_params {
uint16_t sample_validity; // sample lifetime in s

20
libc/dns/resolv/res_mkquery.c
View file

@ -269,8 +269,28 @@ res_nopt(res_state statp,
}
ns_put16(flags, cp);
cp += INT16SZ;
#ifdef EDNS0_PADDING
{
u_int16_t minlen = (cp - buf) + 3 * INT16SZ;
u_int16_t extra = minlen % EDNS0_PADDING;
u_int16_t padlen = (EDNS0_PADDING - extra) % EDNS0_PADDING;
if (minlen > buflen) {
return (-1);
}
padlen = MIN(padlen, buflen - minlen);
ns_put16(padlen + 2 * INT16SZ, cp); /* RDLEN */
cp += INT16SZ;
ns_put16(NS_OPT_PADDING, cp); /* OPTION-CODE */
cp += INT16SZ;
ns_put16(padlen, cp); /* OPTION-LENGTH */
cp += INT16SZ;
memset(cp, 0, padlen);
cp += padlen;
}
#else
ns_put16(0, cp); /* RDLEN */
cp += INT16SZ;
#endif
hp->arcount = htons(ntohs(hp->arcount) + 1);
return (cp - buf);

1
libc/include/arpa/nameser.h
View file

@ -474,6 +474,7 @@ typedef enum __ns_cert_types {
*/
#define NS_OPT_DNSSEC_OK 0x8000U
#define NS_OPT_NSID 3
#define NS_OPT_PADDING 12
/*
* Inline versions of get/put short/long. Pointer is advanced.