If OpenSSL fails to generate an RSA key, do not retain a dangling
pointer to the previous (uninitialized) key value. The impact here
should be limited to a difficult-to-trigger crash, if OpenSSL is
running an engine that makes key generation failures possible, or if
OpenSSL runs out of memory. Fixes bug 19152; bugfix on
0.2.1.10-alpha. Found by Yuan Jochen Kang, Suman Jana, and Baishakhi
Ray.
This is potentially scary stuff, so let me walk through my analysis.
I think this is a bug, and a backport candidate, but not remotely
triggerable in any useful way.
Observation 1a:
Looking over the OpenSSL code here, the only way we can really fail in
the non-engine case is if malloc() fails. But if malloc() is failing,
then tor_malloc() calls should be tor_asserting -- the only way that an
attacker could do an exploit here would be to figure out some way to
make malloc() fail when openssl does it, but work whenever Tor does it.
(Also ordinary malloc() doesn't fail on platforms like Linux that
overcommit.)
Observation 1b:
Although engines are _allowed_ to fail in extra ways, I can't find much
evidence online that they actually _do_ fail in practice. More evidence
would be nice, though.
Observation 2:
We don't call crypto_pk_generate*() all that often, and we don't do it
in response to external inputs. The only way to get it to happen
remotely would be by causing a hidden service to build new introduction
points.
Observation 3a:
So, let's assume that both of the above observations are wrong, and the
attacker can make us generate a crypto_pk_env_t with a dangling pointer
in its 'key' field, and not immediately crash.
This dangling pointer will point to what used to be an RSA structure,
with the fields all set to NULL. Actually using this RSA structure,
before the memory is reused for anything else, will cause a crash.
In nearly every function where we call crypto_pk_generate*(), we quickly
use the RSA key pointer -- either to sign something, or to encode the
key, or to free the key. The only exception is when we generate an
intro key in rend_consider_services_intro_points(). In that case, we
don't actually use the key until the intro circuit is opened -- at which
point we encode it, and use it to sign an introduction request.
So in order to exploit this bug to do anything besides crash Tor, the
attacker needs to make sure that by the time the introduction circuit
completes, either:
* the e, d, and n BNs look valid, and at least one of the other BNs is
still NULL.
OR
* all 8 of the BNs must look valid.
To look like a valid BN, *they* all need to have their 'top' index plus
their 'd' pointer indicate an addressable region in memory.
So actually getting useful data of of this, rather than a crash, is
going to be pretty damn hard. You'd have to force an introduction point
to be created (or wait for one to be created), and force that particular
crypto_pk_generate*() to fail, and then arrange for the memory that the
RSA points to to in turn point to 3...8 valid BNs, all by the time the
introduction circuit completes.
Naturally, the signature won't check as valid [*], so the intro point
will reject the ESTABLISH_INTRO cell. So you need to _be_ the
introduction point, or you don't actually see this information.
[*] Okay, so if you could somehow make the 'rsa' pointer point to a
different valid RSA key, then you'd get a valid signature of an
ESTABLISH_INTRO cell using a key that was supposed to be used for
something else ... but nothing else looks like that, so you can't use
that signature elsewhere.
Observation 3b:
Your best bet as an attacker would be to make the dangling RSA pointer
actually contain a fake method, with a fake RSA_private_encrypt
function that actually pointed to code you wanted to execute. You'd
still need to transit 3 or 4 pointers deep though in order to make that
work.
Conclusion:
By 1, you probably can't trigger this without Tor crashing from OOM.
By 2, you probably can't trigger this reliably.
By 3, even if I'm wrong about 1 and 2, you have to jump through a pretty
big array of hoops in order to get any kind of data leak or code
execution.
So I'm calling it a bug, but not a security hole. Still worth
patching.
The problem is that "q" is always set on the first iteration even
if the question is not a supported question. This set of "q" is
not necessary, and will be handled after exiting the loop if there
if a supported q->type was found.
[Changes file by nickm]
lease enter the commit message for your changes. Lines starting
This closes bug 18162; bugfix on a45b131590, which fixed a related
issue long ago.
In addition to the #18162 issues, this fixes a signed integer overflow
in smarltist_add_all(), which is probably not so great either.
Check size argument to memwipe() for underflow.
Closes bug #18089. Reported by "gk", patch by "teor".
Bugfix on 0.2.3.25 and 0.2.4.6-alpha (#7352),
commit 49dd5ef3 on 7 Nov 2012.
There was a dead check when we made sure that an array member of a
struct was non-NULL. Tor has been doing this check since at least
0.2.3, maybe earlier.
Fixes bug 17781.
Previously we'd suppressed the mask-bits field in the output when
formatting a policy if it was >=32. But that should be a >=128 if
we're talking about IPv6.
Since we didn't put these in descriptors, this bug affects only log
messages and controller outputs.
Fix for bug 16056. The code in question was new in 0.2.0, but the
bug was introduced in 0.2.4 when we started supporting IPv6 exits.
The wrong list was used when looking up expired intro points in a rend
service object causing what we think could be reachability issues and
triggering a BUG log.
Fixes#16702
Signed-off-by: David Goulet <dgoulet@ev0ke.net>
Without this check, we potentially look up to 3 characters before
the start of a malloc'd segment, which could provoke a crash under
certain (weird afaik) circumstances.
Fixes 17404; bugfix on 0.2.6.3-alpha.
* Don't assume that every test box has an IPv4 address
* Don't assume that every test box has a non-local address
Resolves issue #17255 released in unit tests in 0.2.7.3-rc.
Now that x509_get_not{Before,After} are functions in OpenSSL 1.1
(not yet releasesd), we need to define a variant that takes a const
pointer to X509 and returns a const pointer to ASN1_time.
Part of 17237. I'm not convinced this is an openssl bug or a tor
bug. It might be just one of those things.
Ensure that either a valid address is returned in address pointers,
or that the address data is zeroed on error.
Ensure that free_interface_address6_list handles NULL lists.
Add unit tests for get_interface_address* failure cases.
Fixes bug #17173.
Patch by fk/teor, not in any released version of tor.
Use environment variables instead. This repairs 'make distcheck',
which was running into trouble when it tried to chmod the generated
scripts.
Fixes 17148.
This allows builds on machines with a crippled openssl to fail early
during configure. Bugfix on 0.2.7.1-alpha, which introduced the
requirement for ECC support. Fixes bug 17109.
Advise users how to configure separate IPv4 and IPv6 exit
policies in the manpage and sample torrcs.
Related to fixes in ticket #16069 and #17027. Patch by "teor".
Patch on 2eb7eafc9d and a96c0affcb (25 Oct 2012),
released in 0.2.4.7-alpha.
src/test/test_policy.c:
Merged calls to policies_parse_exit_policy by adding additional arguments.
fixup to remaining instance of ~EXIT_POLICY_IPV6_ENABLED.
Compacting logic test now produces previous list length of 4, corrected this.
src/config/torrc.sample.in:
src/config/torrc.minimal.in-staging:
Merged torrc modification dates in favour of latest.
ExitPolicyRejectPrivate now rejects more local addresses by default:
* the relay's published IPv6 address (if any), and
* any publicly routable IPv4 or IPv6 addresses on any local interfaces.
This resolves a security issue for IPv6 Exits and multihomed Exits that
trust connections originating from localhost.
Resolves ticket 17027. Patch by "teor".
Patch on 42b8fb5a15 (11 Nov 2007), released in 0.2.0.11-alpha.
In previous versions of Tor, ExitPolicy accept6/reject6 * produced
policy entries for IPv4 and IPv6 wildcard addresses.
To reduce operator confusion, change accept6/reject6 * to only produce
an IPv6 wildcard address.
Resolves bug #16069.
Patch on 2eb7eafc9d and a96c0affcb (25 Oct 2012),
released in 0.2.4.7-alpha.
Tor now warns when ExitPolicy lines occur after accept/reject *:*
or variants. These lines are redundant, and were always ignored.
Partial fix for ticket 16069. Patch by "teor".
Patch on 2eb7eafc9d and a96c0affcb (25 Oct 2012),
released in 0.2.4.7-alpha.
When parsing torrc ExitPolicies, we now warn if:
* an IPv4 address is used on an accept6 or reject6 line. The line is
ignored, but the rest of the policy items in the list are used.
(accept/reject continue to allow both IPv4 and IPv6 addresses in torrcs.)
* a "private" address alias is used on an accept6 or reject6 line.
The line filters both IPv4 and IPv6 private addresses, disregarding
the 6 in accept6/reject6.
When parsing torrc ExitPolicies, we now issue an info-level message:
* when expanding an accept/reject * line to include both IPv4 and IPv6
wildcard addresses.
In each instance, usage advice is provided to avoid the message.
Partial fix for ticket 16069. Patch by "teor".
Patch on 2eb7eafc9d and a96c0affcb (25 Oct 2012),
released in 0.2.4.7-alpha.
Add get_interface_address[6]_list by refactoring
get_interface_address6. Add unit tests for new and existing functions.
Preparation for ticket 17027. Patch by "teor".
Patch on 42b8fb5a15 (11 Nov 2007), released in 0.2.0.11-alpha.
This controls the circuit dirtyness reset behavior added for Tor
Browser's user experience fix (#15482). Unlike previous iterations
of this patch, the tunable actually works, and is documented.
(These inputs are possible when Shadow starts the world at time_t 0,
and breaks our assumption that Tor didn't exist in the 1970s.)
Fixes regression introduced in 241e6b09. Fixes#16980.
When this is set, and Tor is running as a relay, it will not
generate or load its secret identity key. You can manage the secret
identity key with --keygen. Implements ticket 16944.
In a nutshell, since a circuit can not exit at its entry point, it's very
easy for an attacker to find the hidden service guard if only one EntryNodes
is specified since for that guard, the HS will refuse to build a rendezvous
circuit to it.
For now, the best solution is to stop tor to allow a single EntryNodes for
an hidden service.
Fixes#14917
Signed-off-by: David Goulet <dgoulet@ev0ke.net>
Make "bridges+hs" the default test network. This tests almost all
tor functionality during make test-network, while allowing tests
to succeed on non-IPv6 systems.
Requires chutney commit 396da92 in test-network-bridges-hs.
Closes tickets 16945 (tor), 16946 (chutney) . Patches by "teor".
Previously we'd put these strings right on the controllers'
outbufs. But this could cause some trouble, for these reasons:
1) Calling the network stack directly here would make a huge portion
of our networking code (from which so much of the rest of Tor is
reachable) reachable from everything that potentially generated
controller events.
2) Since _some_ events (EVENT_ERR for instance) would cause us to
call connection_flush(), every control_event_* function would
appear to be able to reach even _more_ of the network stack in
our cllgraph.
3) Every time we generated an event, we'd have to walk the whole
connection list, which isn't exactly fast.
This is an attempt to break down the "blob" described in
http://archives.seul.org/tor/dev/Mar-2015/msg00197.html -- the set of
functions from which nearly all the other functions in Tor are
reachable.
Closes ticket 16695.
Nick Mathewson
Karsten Loesing
Scott Dial
teor (Tim Wilson-Brown)
Roger Dingledine
Arlo Breault
cypherpunks
David Goulet
Sebastian Hahn
Yawning Angel
rl1987
Andreas Stieger