diff options
author | Geoff Thorpe <geoff@openssl.org> | 2014-04-30 11:39:24 -0400 |
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committer | Geoff Thorpe <geoff@openssl.org> | 2014-04-30 11:53:09 -0400 |
commit | 3cc546a3bbcbf26cd14fc45fb133d36820ed0a75 (patch) | |
tree | 874dfddbe67b384fe9e6804523cbda677a07deb9 /crypto/bn | |
parent | c434f7f80fdbb7c7359eb957549c3ba07255bf26 (diff) |
bignum: fix boundary condition in montgomery logic
It's not clear whether this inconsistency could lead to an actual
computation error, but it involved a BIGNUM being passed around the
montgomery logic in an inconsistent state. This was found using flags
-DBN_DEBUG -DBN_DEBUG_RAND, and working backwards from this assertion
in 'ectest';
ectest: bn_mul.c:960: BN_mul: Assertion `(_bnum2->top == 0) ||
(_bnum2->d[_bnum2->top - 1] != 0)' failed
Signed-off-by: Geoff Thorpe <geoff@openssl.org>
(cherry picked from commit a52926189155d906d8c11ff97cbc1e5191d202cd)
Diffstat (limited to 'crypto/bn')
-rw-r--r-- | crypto/bn/bn_exp.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/crypto/bn/bn_exp.c b/crypto/bn/bn_exp.c index 5adb441870..3fa8cda842 100644 --- a/crypto/bn/bn_exp.c +++ b/crypto/bn/bn_exp.c @@ -493,6 +493,9 @@ int BN_mod_exp_mont(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p, r->d[0] = (0-m->d[0])&BN_MASK2; for(i=1;i<j;i++) r->d[i] = (~m->d[i])&BN_MASK2; r->top = j; + /* Upper words will be zero if the corresponding words of 'm' + * were 0xfff[...], so decrement r->top accordingly. */ + bn_correct_top(r); } else #endif |