The 'restrict' keyword was introduced in C99 and provides a hint to
the compiler that can be used to better optimized code. The 'restrict'
keyword results in build failures when the compiler is not C99.
auditdns.c:101:37: error: expected ‘;’, ‘,’ or ‘)’ before ‘hints’
const struct addrinfo *restrict hints,
^
auditdns.c:409:45: error: expected ‘;’, ‘,’ or ‘)’ before ‘sa’
getnameinfo(const struct sockaddr *restrict sa, socklen_t salen,
^
This change defines 'register' to nothing if the compiler does not
implement the C99 standard.
Observed with gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-44).
This change has two parts:
1. Provide our own local implementation of numeric-only getaddrinfo
in auditdns.c used to audit for DNS leaks, rather than deferring
to dlsym(RTLD_NEXT, "getaddrinfo"), in terms of inet_pton.
To keep review and implementation simple, this is limited to
AI_NUMERICHOST _and_ AI_NUMERICSERV -- this requires that we
arrange to pass AI_NUMERICSERV in callers too.
2. Wherever we implement block_dns, set AI_NUMERICSERV in addition to
AI_NUMERICHOST as needed by the new auditdns.c getaddrinfo.
(In principle this might also avoid other network leaks -- POSIX
guarantees no name resolution service will be invoked, and gives
NIS+ as an example.)
One tiny semantic change to avoid tripping over the auditor:
kadmin(8) now uses the string "749" rather than the string
"kerberos-adm". (Currently we don't audit kadmin(8) for DNS leaks
but let's avoid leaving a rake to step on.) Every other caller I
found is already guaranteed to pass a numeric service rather than
named service to getaddrinfo.
fix https://github.com/heimdal/heimdal/issues/1212
We build variants of kinit and test_acquire_cred that define their
own symbols rk_dns_lookup, gethostbyname, gethostbyname2, and
getaddrinfo to print a message and abort. For getaddrinfo, we abort
only if the caller failed to specify AI_NUMERICHOST; otherwise we use
dlsym(RTLD_NEXT, "getaddrinfo") instead.
The new test tests/gss/check-nodns is like tests/gss/check-basic, but
uses kinit_auditdns and test_acquire_cred_auditdns to verify that no
DNS resolution happens.
This test should work and be effective on ELF platforms where the
getaddrinfo function is implemented by the symbol `getaddrinfo'. On
non-ELF platforms it may not be effective -- and on platforms where
the getaddrinfo function is implemented by another symbol (like
`__getaddrinfo50') it may not work, but we can cross that bridge when
we come to it.
Verified manually that the test fails, with the expected error
message and abort, without `block_dns = yes' in krb5-nodns.conf. No
automatic test of the mechanism for now because it might not work on
some platforms.
XXX check-nodns.in is copypasta of check-basic.in, should factor out
the common parts so they don't get out of sync.
