Return an error from BN_mod_inverse if n is 1 (or -1) #6119
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Calculating BN_mod_inverse where n is 1 (or -1) doesn't make sense. We should return an error in that case. Instead we were returning a valid result with value 0. Fixes openssl#6004
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Ping @openssl/committers. Thoughts please! |
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Fix it. It's a math error. |
mattcaswell
changed the title
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Taken out of WIP. |
richsalz
approved these changes
May 2, 2018
mattcaswell
added
branch: master
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Forgot to add target branch labels. @richsalz are you ok for backport to 1.1.0? It cherry-picks cleanly. |
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Yes, I am fine with merging to other branches. |
richsalz
added
the
approval: done
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Pushed to master and 1.1.0. Thanks. |
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Calculating BN_mod_inverse where n is 1 (or -1) doesn't make sense. We
should return an error in that case. Instead we were returning a valid
result with value 0.
Fixes #6004
I've marked this as WIP because I'd like some feedback on this. It turns out that, even though it doesn't make any sense to ask for BN_mod_inverse() with n set to 1 we were doing it anyway - and rely on the fact that the result is 0. I have fixed the instance where that occurred, but it made me worry that if we are doing it, are there other applications doing it too (which we would break)?
The alternative to fixing it is to just document the quirk.
Should we fix it or document it?