Mercurial > hg > nginx
changeset 7863:3e78c12d4f37 stable-1.20
Resolver: explicit check for compression pointers in question.
Since nginx always uses exactly one entry in the question section of
a DNS query, and never uses compression pointers in this entry, parsing
of a DNS response in ngx_resolver_process_response() does not expect
compression pointers to appear in the question section of the DNS
response. Indeed, compression pointers in the first name of a DNS response
hardly make sense, do not seem to be allowed by RFC 1035 (which says
"a pointer to a prior occurance of the same name", note "prior"), and
were never observed in practice.
Added an explicit check to ngx_resolver_process_response()'s parsing
of the question section to properly report an error if compression pointers
nevertheless appear in the question section.
author | Maxim Dounin <mdounin@mdounin.ru> |
---|---|
date | Tue, 25 May 2021 15:17:50 +0300 |
parents | 60a1d97bedfe |
children | 39a422cf9876 |
files | src/core/ngx_resolver.c |
diffstat | 1 files changed, 6 insertions(+), 0 deletions(-) [+] |
line wrap: on
line diff
--- a/src/core/ngx_resolver.c Tue May 25 15:17:45 2021 +0300 +++ b/src/core/ngx_resolver.c Tue May 25 15:17:50 2021 +0300 @@ -1798,6 +1798,12 @@ i = sizeof(ngx_resolver_hdr_t); while (i < (ngx_uint_t) n) { + + if (buf[i] & 0xc0) { + err = "unexpected compression pointer in DNS response"; + goto done; + } + if (buf[i] == '\0') { goto found; }