From 730244f49ad8f46308f5513e58365eed370423cb Mon Sep 17 00:00:00 2001 From: Florian Weimer Date: Wed, 27 Apr 2016 16:39:12 +0200 Subject: [PATCH] nss_dns: Check address length before creating addrinfo result [BZ #19831] Previously, we allocated room in the result space before the check, leaving uninitialized data there in case the check failed. This also consolidates the behavior between single (A or AAAA) and dual (A and AAAA in parallel) queries. Single queries checked the record length against the QTYPE, not the RRTYPE. (cherry picked from commit 5e0c421cc07e2d06945b863ed3bb92395472705d) --- ChangeLog | 8 ++++++ resolv/nss_dns/dns-host.c | 59 ++++++++++++++++++++++++++------------- 2 files changed, 47 insertions(+), 20 deletions(-) diff --git a/ChangeLog b/ChangeLog index adc9b65132f..1fef1d5204b 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,11 @@ +2016-04-27 Florian Weimer + + [BZ #19831] + * resolv/nss_dns/dns-host.c (rrtype_to_rdata_length): New + function. + (getanswer_r): Check RDATA length against RRTYPE and QTYPE. + (gaih_getanswer_slice): Check RDATA length against RRTYPE. + 2016-04-27 Florian Weimer [BZ #19862] diff --git a/resolv/nss_dns/dns-host.c b/resolv/nss_dns/dns-host.c index fb1d21cad72..403a0058129 100644 --- a/resolv/nss_dns/dns-host.c +++ b/resolv/nss_dns/dns-host.c @@ -134,6 +134,22 @@ extern enum nss_status _nss_dns_gethostbyname3_r (const char *name, int af, char **canonp); hidden_proto (_nss_dns_gethostbyname3_r) +/* Return the expected RDATA length for an address record type (A or + AAAA). */ +static int +rrtype_to_rdata_length (int type) +{ + switch (type) + { + case T_A: + return INADDRSZ; + case T_AAAA: + return IN6ADDRSZ; + default: + return -1; + } +} + enum nss_status _nss_dns_gethostbyname3_r (const char *name, int af, struct hostent *result, char *buffer, size_t buflen, int *errnop, @@ -888,6 +904,15 @@ getanswer_r (const querybuf *answer, int anslen, const char *qname, int qtype, cp += n; continue; /* XXX - had_error++ ? */ } + + /* Stop parsing at a record whose length is incorrect. */ + if (n != rrtype_to_rdata_length (type)) + { + ++had_error; + break; + } + + /* Skip records of the wrong type. */ if (n != result->h_length) { cp += n; @@ -1124,25 +1149,25 @@ gaih_getanswer_slice (const querybuf *answer, int anslen, const char *qname, } continue; } -#if 1 - // We should not see any types other than those explicitly listed - // below. Some types sent by server seem missing, though. Just - // collect the data for now. - if (__glibc_unlikely (type != T_A && type != T_AAAA)) -#else - if (__builtin_expect (type == T_SIG, 0) - || __builtin_expect (type == T_KEY, 0) - || __builtin_expect (type == T_NXT, 0) - || __builtin_expect (type == T_PTR, 0) - || __builtin_expect (type == T_DNAME, 0)) -#endif + + /* Stop parsing if we encounter a record with incorrect RDATA + length. */ + if (type == T_A || type == T_AAAA) + { + if (n != rrtype_to_rdata_length (type)) + { + ++had_error; + continue; + } + } + else { + /* Skip unknown records. */ cp += n; continue; } - if (type != T_A && type != T_AAAA) - abort (); + assert (type == T_A || type == T_AAAA); if (*pat == NULL) { uintptr_t pad = (-(uintptr_t) buffer @@ -1176,12 +1201,6 @@ gaih_getanswer_slice (const querybuf *answer, int anslen, const char *qname, } (*pat)->family = type == T_A ? AF_INET : AF_INET6; - if (__builtin_expect ((type == T_A && n != INADDRSZ) - || (type == T_AAAA && n != IN6ADDRSZ), 0)) - { - ++had_error; - continue; - } memcpy ((*pat)->addr, cp, n); cp += n; (*pat)->scopeid = 0; -- 2.47.2