| 1 | =pod
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| 2 |
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| 3 | =head1 NAME
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| 4 |
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| 5 | BN_CTX_new_ex, BN_CTX_new, BN_CTX_secure_new_ex, BN_CTX_secure_new, BN_CTX_free
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| 6 | - allocate and free BN_CTX structures
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| 7 |
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| 8 | =head1 SYNOPSIS
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| 9 |
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| 10 | #include <openssl/bn.h>
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| 11 |
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| 12 | BN_CTX *BN_CTX_new_ex(OSSL_LIB_CTX *ctx);
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| 13 | BN_CTX *BN_CTX_new(void);
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| 14 |
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| 15 | BN_CTX *BN_CTX_secure_new_ex(OSSL_LIB_CTX *ctx);
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| 16 | BN_CTX *BN_CTX_secure_new(void);
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| 17 |
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| 18 | void BN_CTX_free(BN_CTX *c);
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| 19 |
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| 20 | =head1 DESCRIPTION
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| 21 |
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| 22 | A B<BN_CTX> is a structure that holds B<BIGNUM> temporary variables used by
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| 23 | library functions. Since dynamic memory allocation to create B<BIGNUM>s
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| 24 | is rather expensive when used in conjunction with repeated subroutine
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| 25 | calls, the B<BN_CTX> structure is used.
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| 26 |
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| 27 | BN_CTX_new_ex() allocates and initializes a B<BN_CTX> structure for the given
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| 28 | library context B<ctx>. The <ctx> value may be NULL in which case the default
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| 29 | library context will be used. BN_CTX_new() is the same as BN_CTX_new_ex() except
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| 30 | that the default library context is always used.
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| 31 |
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| 32 | BN_CTX_secure_new_ex() allocates and initializes a B<BN_CTX> structure
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| 33 | but uses the secure heap (see L<CRYPTO_secure_malloc(3)>) to hold the
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| 34 | B<BIGNUM>s for the given library context B<ctx>. The <ctx> value may be NULL in
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| 35 | which case the default library context will be used. BN_CTX_secure_new() is the
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| 36 | same as BN_CTX_secure_new_ex() except that the default library context is always
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| 37 | used.
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| 38 |
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| 39 | BN_CTX_free() frees the components of the B<BN_CTX> and the structure itself.
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| 40 | Since BN_CTX_start() is required in order to obtain B<BIGNUM>s from the
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| 41 | B<BN_CTX>, in most cases BN_CTX_end() must be called before the B<BN_CTX> may
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| 42 | be freed by BN_CTX_free(). If B<c> is NULL, nothing is done.
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| 43 |
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| 44 | A given B<BN_CTX> must only be used by a single thread of execution. No
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| 45 | locking is performed, and the internal pool allocator will not properly handle
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| 46 | multiple threads of execution.
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| 47 |
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| 48 | =head1 RETURN VALUES
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| 49 |
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| 50 | BN_CTX_new() and BN_CTX_secure_new() return a pointer to the B<BN_CTX>.
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| 51 | If the allocation fails,
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| 52 | they return B<NULL> and sets an error code that can be obtained by
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| 53 | L<ERR_get_error(3)>.
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| 54 |
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| 55 | BN_CTX_free() has no return values.
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| 56 |
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| 57 | =head1 REMOVED FUNCTIONALITY
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| 58 |
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| 59 | void BN_CTX_init(BN_CTX *c);
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| 60 |
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| 61 | BN_CTX_init() is no longer available as of OpenSSL 1.1.0. Applications should
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| 62 | replace use of BN_CTX_init with BN_CTX_new instead:
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| 63 |
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| 64 | BN_CTX *ctx;
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| 65 | ctx = BN_CTX_new();
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| 66 | if (!ctx)
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| 67 | /* error */
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| 68 | ...
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| 69 | BN_CTX_free(ctx);
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| 70 |
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| 71 | =head1 SEE ALSO
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| 72 |
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| 73 | L<ERR_get_error(3)>, L<BN_add(3)>,
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| 74 | L<BN_CTX_start(3)>
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| 75 |
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| 76 | =head1 HISTORY
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| 77 |
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| 78 | BN_CTX_init() was removed in OpenSSL 1.1.0.
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| 79 |
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| 80 | =head1 COPYRIGHT
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| 81 |
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| 82 | Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved.
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| 83 |
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| 84 | Licensed under the Apache License 2.0 (the "License"). You may not use
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| 85 | this file except in compliance with the License. You can obtain a copy
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| 86 | in the file LICENSE in the source distribution or at
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| 87 | L<https://www.openssl.org/source/license.html>.
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| 88 |
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| 89 | =cut
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