timing attacks.
BN_FLG_EXP_CONSTTIME requests this algorithm, and this done by default for
RSA/DSA/DH private key computations unless
RSA_FLAG_NO_EXP_CONSTTIME/DSA_FLAG_NO_EXP_CONSTTIME/
DH_FLAG_NO_EXP_CONSTTIME is set.
Submitted by: Matthew D Wood
Reviewed by: Bodo Moeller
- possibility of re-creation of the blinding parameters after a
fixed number of uses (suggested by Bodo)
- calculatition of the rsa::e in case it's absent and p and q
are present (see bug report #785)
- improve the performance when if one rsa structure is shared by
more than a thread (see bug report #555)
- fix the problem described in bug report #827
- hide the definition ot the BN_BLINDING structure in bn_blind.c
COFF and a.out targets [similar to ELF targets]. You might notice some
rudementary support for shared mingw builds under cygwin. It works (it
produces cryptoeay32.dll and ssleay32.dll with everything exported by
name), but it's primarily for testing/debugging purposes, at least for
now...
- Remove unused and unuseful debug cruft.
- Remove unnecessary 'top' fudging from BN_copy().
- Fix a potential memory leak and simplify the expansion logic in
BN_bin2bn().
Submitted by: Nils Larsch
Reviewed by: Geoff Thorpe
Yet another question: some time ago you changed BN_set_word.
Why didn't you change BN_get_word as well?
Quite. I'm also removing the older commented-out implementations to improve
readability. This complex stuff seems to date from a time when the types
didn't match up well.
Submitted by: Nils Larsch, Geoff Thorpe
the only function that uses it) because it would trip up an assertion in
bn_div_words() when first invoked. This also adds BN_div_word() testing to
bntest.
Submitted by: Nils Larsch
Reviewed by: Geoff Thorpe
corresponding headers are only required for API functions or structure
details. This now includes the bignum types and BUF_MEM. Subsequent commits
will remove various dependencies on bn.h and buffer.h and update the
makefile dependencies.
especially for AIX. But most important BIGNUM assembler implementation
submitted by IBM.
Submitted by: Peter Waltenberg <pwalten@au1.ibm.com>
Reviewed by: appro
locally initialising their own.
NB: I've removed the "BN_clear_free()" loops for the exit-paths in some of
these functions, and that may be a major part of the performance
improvements we're seeing. The "free" part can be removed because we're
using BN_CTX. The "clear" part OTOH can be removed because BN_CTX
destruction automatically performs this task, so performing it inside
functions that may be called repeatedly is wasteful. This is currently safe
within openssl due to the fact that BN_CTX objects are never created for
longer than a single high-level operation. However, that is only because
there's currently no mechanism in openssl for thread-local storage. Beyond
that, this might be an issue for applications using the bignum API directly
and caching their own BN_CTX objects. The solution is to introduce a flag
to BN_CTX_start() that allows its variables to be automatically sanitised
on release during BN_CTX_end(). This way any higher-level function (and
perhaps the application) can specify this flag in its own
BN_CTX_start()/BN_CTX_end() pair, and this will cause inner-loop functions
specifying the flag to be ignored so that sanitisation is handled only once
back out at the higher level. I will be implementing this in the near
future.
little TODO list in there as well as the debugging code (only enabled if
BN_CTX_DEBUG is defined).
I'd appreciate as much review and testing as can be spared for this. I'll
commit some changes to other parts of the bignum code shortly to make
better use of this implementation (no more fixed size limitations). Note
also that under identical optimisations, I'm seeing a noticable speed
increase over openssl-0.9.7 - so any feedback to confirm/deny this on other
systems would also be most welcome.
- Remove some unnecessary "+1"-like fudges. Sizes should be handled
exactly, as enlarging size parameters causes needless bloat and may just
make bugs less likely rather than fixing them: bn_expand() macro,
bn_expand_internal(), and BN_sqr().
- Deprecate bn_dup_expand() - it's new since 0.9.7, unused, and not that
useful.
- Remove unnecessary zeroing of unused bytes in bn_expand2().
- Rewrite BN_set_word() - it should be much simpler, the previous
complexities probably date from old mismatched type issues.
- Add missing bn_check_top() macros in bn_word.c
- Improve some degenerate case handling in BN_[add|sub]_word(), add
comments, and avoid a bignum expansion if an overflow isn't possible.
Remove certain redundant BN_zero() initialisations, because BN_CTX_get(),
BN_init(), [etc] already initialise to zero.
Correct error checking in bn_sqr.c, and be less wishy-wash about how/why
the result's 'top' value is set (note also, 'max' is always > 0 at this
point).
bignums are passed in and out of functions and APIs in a consistent form
has highlighted that zero-valued bignums don't need any allocated word
data. The use of BN_set_word() to initialise a bignum to zero causes
needless allocation and gives it a return value that must be checked. This
change converts BN_zero() to a self-contained macro that has no
return/expression value and does not cause any expansion of bignum data.
Note, it would be tempting to rewrite the deprecated version as a
success-valued comma expression, such as;
#define BN_zero(a) ((a)->top = (a)->neg = 0, 1)
However, this evaluates 'a' twice and would confuse initialisation loops
(eg. while(..) { BN_zero(bn++) } ). As such, the deprecated version
continues to use BN_set_word().
redefine bn_clear_top2max() to be a NOP in the non-debugging case, and
remove some unnecessary usages in bn_nist.c.
Submitted by: Nils Larsch
Reviewed by: Geoff Thorpe, Ulf Möller
return a "zero" bignum as BN_new() does - so reset 'top'. During
BN_CTX_end(), released bignums should be consistent so enforce this in
debug builds. Also, reduce the number of wasted BN_clear_free() calls from
BN_CTX_end() (typically by 75% or so).
Submitted by: Nils Larsch
Reviewed by: Geoff Thorpe, Ulf Möller
