1a9499cf23
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>
(cherry picked from commit 7cc18d8158)
Conflicts:
crypto/bn/bn.h
crypto/bn/bn_err.c
66 lines
1.9 KiB
Text
66 lines
1.9 KiB
Text
=pod
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=head1 NAME
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BN_set_bit, BN_clear_bit, BN_is_bit_set, BN_mask_bits, BN_lshift,
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BN_lshift1, BN_rshift, BN_rshift1 - bit operations on BIGNUMs
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=head1 SYNOPSIS
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#include <openssl/bn.h>
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int BN_set_bit(BIGNUM *a, int n);
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int BN_clear_bit(BIGNUM *a, int n);
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int BN_is_bit_set(const BIGNUM *a, int n);
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int BN_mask_bits(BIGNUM *a, int n);
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int BN_lshift(BIGNUM *r, const BIGNUM *a, int n);
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int BN_lshift1(BIGNUM *r, BIGNUM *a);
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int BN_rshift(BIGNUM *r, BIGNUM *a, int n);
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int BN_rshift1(BIGNUM *r, BIGNUM *a);
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=head1 DESCRIPTION
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BN_set_bit() sets bit B<n> in B<a> to 1 (C<a|=(1E<lt>E<lt>n)>). The
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number is expanded if necessary.
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BN_clear_bit() sets bit B<n> in B<a> to 0 (C<a&=~(1E<lt>E<lt>n)>). An
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error occurs if B<a> is shorter than B<n> bits.
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BN_is_bit_set() tests if bit B<n> in B<a> is set.
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BN_mask_bits() truncates B<a> to an B<n> bit number
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(C<a&=~((~0)E<gt>E<gt>n)>). An error occurs if B<a> already is
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shorter than B<n> bits.
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BN_lshift() shifts B<a> left by B<n> bits and places the result in
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B<r> (C<r=a*2^n>). Note that B<n> must be non-negative. BN_lshift1() shifts
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B<a> left by one and places the result in B<r> (C<r=2*a>).
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BN_rshift() shifts B<a> right by B<n> bits and places the result in
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B<r> (C<r=a/2^n>). Note that B<n> must be non-negative. BN_rshift1() shifts
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B<a> right by one and places the result in B<r> (C<r=a/2>).
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For the shift functions, B<r> and B<a> may be the same variable.
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=head1 RETURN VALUES
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BN_is_bit_set() returns 1 if the bit is set, 0 otherwise.
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All other functions return 1 for success, 0 on error. The error codes
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can be obtained by L<ERR_get_error(3)|ERR_get_error(3)>.
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=head1 SEE ALSO
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L<bn(3)|bn(3)>, L<BN_num_bytes(3)|BN_num_bytes(3)>, L<BN_add(3)|BN_add(3)>
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=head1 HISTORY
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BN_set_bit(), BN_clear_bit(), BN_is_bit_set(), BN_mask_bits(),
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BN_lshift(), BN_lshift1(), BN_rshift(), and BN_rshift1() are available
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in all versions of SSLeay and OpenSSL.
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=cut
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