Revision a520723f29aac6598ff0d69e34f5e9b88213e511 authored by Matt Caswell on 14 October 2016, 12:07:00 UTC, committed by Matt Caswell on 28 October 2016, 08:43:41 UTC
The previous commit inspired a review of all the length checks for the extension adding code. This adds more robust checks and adds checks where some were missing previously. The real solution for this is to use WPACKET which is currently in master - but that cannot be applied to release branches. Reviewed-by: Rich Salz <rsalz@openssl.org>
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BN_CTX_start.pod
=pod
=head1 NAME
BN_CTX_start, BN_CTX_get, BN_CTX_end - use temporary BIGNUM variables
=head1 SYNOPSIS
#include <openssl/bn.h>
void BN_CTX_start(BN_CTX *ctx);
BIGNUM *BN_CTX_get(BN_CTX *ctx);
void BN_CTX_end(BN_CTX *ctx);
=head1 DESCRIPTION
These functions are used to obtain temporary B<BIGNUM> variables from
a B<BN_CTX> (which can been created by using L<BN_CTX_new(3)|BN_CTX_new(3)>)
in order to save the overhead of repeatedly creating and
freeing B<BIGNUM>s in functions that are called from inside a loop.
A function must call BN_CTX_start() first. Then, BN_CTX_get() may be
called repeatedly to obtain temporary B<BIGNUM>s. All BN_CTX_get()
calls must be made before calling any other functions that use the
B<ctx> as an argument.
Finally, BN_CTX_end() must be called before returning from the function.
When BN_CTX_end() is called, the B<BIGNUM> pointers obtained from
BN_CTX_get() become invalid.
=head1 RETURN VALUES
BN_CTX_start() and BN_CTX_end() return no values.
BN_CTX_get() returns a pointer to the B<BIGNUM>, or B<NULL> on error.
Once BN_CTX_get() has failed, the subsequent calls will return B<NULL>
as well, so it is sufficient to check the return value of the last
BN_CTX_get() call. In case of an error, an error code is set, which
can be obtained by L<ERR_get_error(3)|ERR_get_error(3)>.
=head1 SEE ALSO
L<BN_CTX_new(3)|BN_CTX_new(3)>
=head1 HISTORY
BN_CTX_start(), BN_CTX_get() and BN_CTX_end() were added in OpenSSL 0.9.5.
=cut
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