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Reject negative shifts for BN_rshift and BN_lshift

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The functions BN_rshift and BN_lshift shift their arguments to the right or
left by a specified number of bits. Unpredicatable results (including
crashes) can occur if a negative number is supplied for the shift value.

Thanks to Mateusz Kocielski (LogicalTrust), Marek Kroemeke and Filip Palian
for discovering and reporting this issue.

Reviewed-by: Kurt Roeckx <kurt@openssl.org>
This commit is contained in:
Matt Caswell
2015-05-19 15:19:30 +01:00
parent 2c55a0bc93
commit 7cc18d8158
4 changed files with 20 additions and 4 deletions
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8
doc/crypto/BN_set_bit.pod
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@@ -37,12 +37,12 @@ BN_mask_bits() truncates B<a> to an B<n> bit number
shorter than B<n> bits.
BN_lshift() shifts B<a> left by B<n> bits and places the result in
B<r> (C<r=a*2^n>). BN_lshift1() shifts B<a> left by one and places
the result in B<r> (C<r=2*a>).
B<r> (C<r=a*2^n>). Note that B<n> must be non-negative. BN_lshift1() shifts
B<a> left by one and places the result in B<r> (C<r=2*a>).
BN_rshift() shifts B<a> right by B<n> bits and places the result in
B<r> (C<r=a/2^n>). BN_rshift1() shifts B<a> right by one and places
the result in B<r> (C<r=a/2>).
B<r> (C<r=a/2^n>). Note that B<n> must be non-negative. BN_rshift1() shifts
B<a> right by one and places the result in B<r> (C<r=a/2>).
For the shift functions, B<r> and B<a> may be the same variable.