Bug 1284207 - uninitialized variable usage with BN_with_flags
uninitialized variable usage with BN_with_flags
Product: Fedora
Classification: Fedora
Component: openssl (Show other bugs)
Unspecified Unspecified
unspecified Severity unspecified
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Assigned To: Tomas Mraz
Fedora Extras Quality Assurance
Depends On:
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Reported: 2015-11-21 18:35 EST by Sami Farin
Modified: 2016-07-19 14:31 EDT (History)
1 user (show)

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Last Closed: 2016-07-19 14:31:00 EDT
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Description Sami Farin 2015-11-21 18:35:28 EST
Description of problem:

/* get a clone of a BIGNUM with changed flags, for *temporary* use only
 * (the two BIGNUMs cannot not be used in parallel!) */
#define BN_with_flags(dest,b,n)  ((dest)->d=(b)->d, \
                                  (dest)->top=(b)->top, \
                                  (dest)->dmax=(b)->dmax, \
                                  (dest)->neg=(b)->neg, \
                                  (dest)->flags=(((dest)->flags & BN_FLG_MALLOCED) \
                                                 |  ((b)->flags & ~BN_FLG_MALLOCED) \
                                                 |  BN_FLG_STATIC_DATA \
                                                 |  (n)))

BN_with_flags is then called with dest being uninitialized variable.
I didn't read enough of the code to say conclusively is double free() possible with current codebase but I'd remove that "((dest)->flags & BN_FLG_MALLOCED) |" from BN_with_flags to be sure and reduce false alarms from static analyzers.
It also uses BN_FLG_STATIC_DATA , well sure,.. openssl is so obvious 😕

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rt.openssl.org said:
  RT Error
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Comment 1 Sami Farin 2015-11-21 19:06:16 EST
Or current users of BN_with_flags could initialize flags before calling it so API stays future-compatible.
Comment 2 Tomas Mraz 2015-11-23 04:43:27 EST
(In reply to Sami Farin from comment #1)
> Or current users of BN_with_flags could initialize flags before calling it
> so API stays future-compatible.

This is the proper fix.

Please report it upstream via mailing to rt@openssl.org
Comment 3 Fedora End Of Life 2016-07-19 14:31:00 EDT
Fedora 22 changed to end-of-life (EOL) status on 2016-07-19. Fedora 22 is
no longer maintained, which means that it will not receive any further
security or bug fix updates. As a result we are closing this bug.

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