In message <[EMAIL PROTECTED]> on Fri, 11 Oct 2002 18:36:44
-0700, David Brumley <[EMAIL PROTECTED]> said:
dbrumley> I've discovered a possible {bug,something unexpected} in
dbrumley> BN_dec2bn() in bn_print.c. I'll call it my "problem" until
dbrumley> confirmed.
[...]
dbrumley> The problem seems to be calling BN_dec2bn with an already
dbrumley> allocated BIGNUM that's been previously used. Inside
dbrumley> BN_dec2bn the code is something like:
dbrumley> int BN_dec2bn(BIGNUM **bn, const char *a){
dbrumley> BIGNUM *ret = NULL;
dbrumley> ...
dbrumley> if(*bn == NULL){
dbrumley> ret = BN_new();
dbrumley> } else {
dbrumley> ret = *bn;
dbrumley> BN_zero(ret); // Call this line a
dbrumley> }
dbrumley> .. yadada ..
dbrumley> while(*a) {
dbrumley> ...
dbrumley> BN_mul_word(ret,BN_DEC_CONV); //call this line b
dbrumley> BN_add_word(ret, l);
dbrumley> ....
dbrumley> }
dbrumley> *bn = ret;
dbrumley> ...
dbrumley> }
dbrumley>
dbrumley> This function appears to want to decide whether or not the
dbrumley> parameter bn has already been allocated.
Correct.
dbrumley> If not, allocated a fresh BIGNUM. If so, zero out the
dbrumley> bignum (e.g. line a). However, BN_zero() doesn't actually
dbrumley> zero out all of the BIGNUM structure, i.e. d[1-top] isn't
dbrumley> zeroed out, only d[0] in struct BIGNUM.
Correct, but it does change top (sets it to 0) as well, so talking
about the range d[1-top] is a moot point.
dbrumley> The problem seems to be manifested in BN_dec2bn() because of
dbrumley> the BN_mul_words and BN_add_words (e.g. line b). Since the
dbrumley> upper parts of d aren't cleared out, those routines end up
dbrumley> adding to whatever junk happened to be left in d from the
dbrumley> previous iteration.
Perhaps there's a bug in those.
Can you send us a small piece of code that actually shows the problem?
Please send us the result that you get, so we can compare.
--
Richard Levitte \ Spannv�gen 38, II \ [EMAIL PROTECTED]
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