1=pod 2 3=head1 NAME 4 5BIO_f_cipher, BIO_set_cipher, BIO_get_cipher_status, BIO_get_cipher_ctx - cipher BIO filter 6 7=head1 SYNOPSIS 8 9=for openssl multiple includes 10 11 #include <openssl/bio.h> 12 #include <openssl/evp.h> 13 14 const BIO_METHOD *BIO_f_cipher(void); 15 int BIO_set_cipher(BIO *b, const EVP_CIPHER *cipher, 16 const unsigned char *key, const unsigned char *iv, int enc); 17 int BIO_get_cipher_status(BIO *b); 18 int BIO_get_cipher_ctx(BIO *b, EVP_CIPHER_CTX **pctx); 19 20=head1 DESCRIPTION 21 22BIO_f_cipher() returns the cipher BIO method. This is a filter 23BIO that encrypts any data written through it, and decrypts any data 24read from it. It is a BIO wrapper for the cipher routines 25EVP_CipherInit(), EVP_CipherUpdate() and EVP_CipherFinal(). 26 27Cipher BIOs do not support BIO_gets() or BIO_puts(). 28 29BIO_flush() on an encryption BIO that is being written through is 30used to signal that no more data is to be encrypted: this is used 31to flush and possibly pad the final block through the BIO. 32 33BIO_set_cipher() sets the cipher of BIO B<b> to B<cipher> using key B<key> 34and IV B<iv>. B<enc> should be set to 1 for encryption and zero for 35decryption. 36 37When reading from an encryption BIO the final block is automatically 38decrypted and checked when EOF is detected. BIO_get_cipher_status() 39is a BIO_ctrl() macro which can be called to determine whether the 40decryption operation was successful. 41 42BIO_get_cipher_ctx() is a BIO_ctrl() macro which retrieves the internal 43BIO cipher context. The retrieved context can be used in conjunction 44with the standard cipher routines to set it up. This is useful when 45BIO_set_cipher() is not flexible enough for the applications needs. 46 47=head1 NOTES 48 49When encrypting BIO_flush() B<must> be called to flush the final block 50through the BIO. If it is not then the final block will fail a subsequent 51decrypt. 52 53When decrypting an error on the final block is signaled by a zero 54return value from the read operation. A successful decrypt followed 55by EOF will also return zero for the final read. BIO_get_cipher_status() 56should be called to determine if the decrypt was successful. 57 58As always, if BIO_gets() or BIO_puts() support is needed then it can 59be achieved by preceding the cipher BIO with a buffering BIO. 60 61=head1 RETURN VALUES 62 63BIO_f_cipher() returns the cipher BIO method. 64 65BIO_set_cipher() returns 1 for success and 0 for failure. 66 67BIO_get_cipher_status() returns 1 for a successful decrypt and <=0 68for failure. 69 70BIO_get_cipher_ctx() returns 1 for success and <=0 for failure. 71 72=head1 COPYRIGHT 73 74Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved. 75 76Licensed under the Apache License 2.0 (the "License"). You may not use 77this file except in compliance with the License. You can obtain a copy 78in the file LICENSE in the source distribution or at 79L<https://www.openssl.org/source/license.html>. 80 81=cut 82