As defined in the C standard:
In all cases the argument is an int, the value of which shall
be representable as an unsigned char or shall equal the value
of the macro EOF. If the argument has any other value, the
behavior is undefined.
This is because they're designed to work with the int values returned
by getc or fgetc; they need extra work to handle a char value.
If EOF is -1 (as it almost always is), with 8-bit bytes, the allowed
inputs to the ctype(3) functions are:
{-1, 0, 1, 2, 3, ..., 255}.
However, on platforms where char is signed, such as x86 with the
usual ABI, code like
char *arg = ...;
... isspace(*arg) ...
may pass in values in the range:
{-128, -127, -126, ..., -2, -1, 0, 1, ..., 127}.
This has two problems:
1. Inputs in the set {-128, -127, -126, ..., -2} are forbidden.
2. The non-EOF byte 0xff is conflated with the value EOF = -1, so
even though the input is not forbidden, it may give the wrong
answer.
Casting char to int first before passing the result to ctype(3)
doesn't help: inputs like -128 are unchanged by this cast. It is
necessary to cast char inputs to unsigned char first; you can then
cast to int if you like but there's no need because the functions
will always convert the argument to int by definition. So the above
fragment needs to be:
char *arg = ...;
... isspace((unsigned char)*arg) ...
This patch inserts unsigned char casts where necessary, and changes
int casts to unsigned char casts where the input is char.
I left alone int casts where the input is unsigned char already --
they're not immediately harmful, although they would have the effect
of suppressing some compiler warnings if the input is ever changed to
be char instead of unsigned char, so it might be better to remove
those casts too.
I also left alone calls where the input is int to begin with because
it came from getc; casting to unsigned char here would be wrong, of
course.
This patch also changes the method of calling querystr() such that
it is only called when logging is enabled, to eliminate any
possible performance problems from searching the larger table.
Try and log exactly what was returned, rather than just what
got cached. Also give validation status of RRsets if extra logging specified.
This commit also fixes a long-standing bug in caching of CNAME chains
leading to a PTR record.
Based on and inspired by a patch from Dominik DL6ER <dl6er@dl6er.de>
This fixes a problem with ipset processing that got recently introduced
when `extract_request` filtering was tightened. During the recent change
an incorrect assumption was made that `extract_request` was only called
for requests but with ipset it is also called when processing responses.
The fix ensures that the new filters only apply to requests (QR=0 @ hdr)
Signed-off-by: Etan Kissling <etan.kissling@gmail.com>
This extends query filtering support beyond what is currently possible
with the `--ipset` configuration option, by adding support for:
1) Specifying allowlists on a per-client basis, based on their
associated Linux connection track mark.
2) Dynamic configuration of allowlists via Ubus.
3) Reporting when a DNS query resolves or is rejected via Ubus.
4) DNS name patterns containing wildcards.
Disallowed queries are not forwarded; they are rejected
with a REFUSED error code.
Signed-off-by: Etan Kissling <etan_kissling@apple.com>
(addressed reviewer feedback)
Signed-off-by: Etan Kissling <etan.kissling@gmail.com>
This should be largely transparent, but it drastically
improves performance and reduces memory foot-print when
configuring large numbers domains of the form
local=/adserver.com/
or
local=/adserver.com/#
Lookup times now grow as log-to-base-2 of the number of domains,
rather than greater than linearly, as before.
The change makes multiple addresses associated with a domain work
address=/example.com/1.2.3.4
address=/example.com/5.6.7.8
It also handles multiple upstream servers for a domain better; using
the same try/retry alogrithms as non domain-specific servers. This
also applies to DNSSEC-generated queries.
Finally, some of the oldest and gnarliest code in dnsmasq has had
a significant clean-up. It's far from perfect, but it _is_ better.
Use the SHA-256 hash function to verify that DNS answers
received are for the questions originally asked. This replaces
the slightly insecure SHA-1 (when compiled with DNSSEC) or
the very insecure CRC32 (otherwise). Refer: CERT VU#434904.
Instead, check only local configured entries are answered without
rdbit set. All cached replies are still denied, but locally configured
names are available with both recursion and without it.
Fixes commit 4139298d28 unintended
behaviour.
Cope with cached and configured CNAMES for all record types we
support, including local-config but not cached types such as TXT.
Also, if we have a locally configured CNAME but no target for the
requested type, don't forward the query.
This moves the class argument to cache-insert into an argument,
rather then overloading a union in the address argument. Note that
tha class is NOT stored in the cache other than for DS/DNSKEY entries,
so must always be C_IN except for these. The data-extraction code
ensures this as it only attempts to cache C_IN class records.
The queries will not be forwarded to a server for a domain, unless
there's a trust anchor provided for that domain. This allows, especially,
suitable proof of non-existance for DS records to come from
the parent domain for domains which are not signed.
Chaos .bind and .server (RFC4892) zones are local, therefore
don't forward queries upstream to avoid mixing with supported
locally and false replies with NO_ID enabled.
This was the source of a large number of #ifdefs, originally
included for use with old embedded libc versions. I'm
sure no-one wants or needs IPv6-free code these days, so this
is a move towards more maintainable code.
Change anti cache-snooping behaviour with queries with the
recursion-desired bit unset. Instead to returning SERVFAIL, we
now always forward, and never answer from the cache. This
allows "dig +trace" command to work.
When a record is defined locally, eg an A record for one.two.example then
we already know that if we forward, eg an AAAA query for one.two.example,
and get back NXDOMAIN, then we need to alter that to NODATA. This is handled
by check_for_local_domain(). But, if we forward two.example, because
one.two.example exists, then the answer to two.example should also be
a NODATA.
For most local records this is easy, just to substring matching.
for A, AAAA and CNAME records that are in the cache, it's more difficult.
The cache has no efficient way to find such records. The fix is to
insert empty (none of F_IPV4, F_IPV6 F_CNAME set) records for each
non-terminal.
The same considerations apply in auth mode, and the same basic mechanism
is used there too.
