getpid() can be really expensive sometimes, and it can fail to
detect some kind of fork+prng mistakes, so we need to avoid it if
it's safe to do so.
This patch might slow down fast_prng a lot on any old operating
system that lacks a way to prevent ram from being inherited, AND
requires a syscall for any getpid() calls. But it should make sure
that we either crash or continue safely on incorrect fork+prng usage
elsewhere in the future.
* Move out code that depends on NSS to crypto_digest_nss.c
* Move out code that depends on OpenSSL to crypto_digest_openssl.c
* Keep the general code that is not specific to any of the above in
crypto_digest.c
This module is currently implemented to use the same technique as
libottery (later used by the bsds' arc4random replacement), using
AES-CTR-256 as its underlying stream cipher. It's backtracking-
resistant immediately after each call, and prediction-resistant
after a while.
Here's how it works:
We generate psuedorandom bytes using AES-CTR-256. We generate BUFLEN bytes
at a time. When we do this, we keep the first SEED_LEN bytes as the key
and the IV for our next invocation of AES_CTR, and yield the remaining
BUFLEN - SEED_LEN bytes to the user as they invoke the PRNG. As we yield
bytes to the user, we clear them from the buffer.
Every RESEED_AFTER times we refill the buffer, we mix in an additional
SEED_LEN bytes from our strong PRNG into the seed.
If the user ever asks for a huge number of bytes at once, we pull SEED_LEN
bytes from the PRNG and use them with our stream cipher to fill the user's
request.
We log these messages at INFO level, except when we are reading a
private key from a file, in which case we log at WARN.
This fixes a regression from when we re-wrote our PEM code to be
generic between nss and openssl.
Fixes bug 29042, bugfix on 0.3.5.1-alpha.
This project introduces the prob_distr.c subsystem which implements all the
probability distributions that WTF-PAD needs. It also adds unittests for all of
them.
Code and tests courtesy of Riastradh.
Co-authored-by: Taylor R Campbell <campbell+tor@mumble.net>
Co-authored-by: Mike Perry <mikeperry-git@torproject.org>
The point of this function is to make sure that the ed25519-based
implementation of curve25519_basepoint() actually works when we
start tor, and use the regular fallback implementation if it
doesn't. But it accounts for 9% of our startup time in the case
when we have directory information, and I think it's safe to make
the test shorter. After all, it has yet to find any actual bugs in
curved25519_scalarmult_basepoint_donna() on any platforms.
Closes ticket 28838.
Allowing this didn't do any actual harm, since there aren't any
shared structures or leakable objects here. Still, it's bad style
and might cause trouble in the future.
Closes ticket 27856.
The trunnel functions are written under the assumption that their
allocators can fail, so GCC LTO thinks they might return NULL. In
point of fact, they're using tor_malloc() and friends, which can't
fail, but GCC won't necessarily figure that out.
Fixes part of #27772.
