BIO_f_cipher(3) OpenSSL BIO_f_cipher(3)
NAME
BIO_f_cipher, BIO_set_cipher, BIO_get_cipher_status, BIO_get_cipher_ctx - cipher BIO filter
SYNOPSIS
#include <openssl/bio.h>
#include <openssl/evp.h>
BIO_METHOD * BIO_f_cipher(void);
void BIO_set_cipher(BIO *b,const EVP_CIPHER *cipher,
unsigned char *key, unsigned char *iv, int enc);
int BIO_get_cipher_status(BIO *b)
int BIO_get_cipher_ctx(BIO *b, EVP_CIPHER_CTX **pctx)
DESCRIPTION
BIO_f_cipher() returns the cipher BIO method. This is a filter BIO that encrypts any data written
through it, and decrypts any data read from it. It is a BIO wrapper for the cipher routines
EVP_CipherInit(), EVP_CipherUpdate() and EVP_CipherFinal().
Cipher BIOs do not support BIO_gets() or BIO_puts().
BIO_flush() on an encryption BIO that is being written through is used to signal that no more data is
to be encrypted: this is used to flush and possibly pad the final block through the BIO.
BIO_set_cipher() sets the cipher of BIO b to cipher using key key and IV iv. enc should be set to 1
for encryption and zero for decryption.
When reading from an encryption BIO the final block is automatically decrypted and checked when EOF
is detected. BIO_get_cipher_status() is a BIO_ctrl() macro which can be called to determine whether
the decryption operation was successful.
BIO_get_cipher_ctx() is a BIO_ctrl() macro which retrieves the internal BIO cipher context. The
retrieved context can be used in conjunction with the standard cipher routines to set it up. This is
useful when BIO_set_cipher() is not flexible enough for the applications needs.
NOTES
When encrypting BIO_flush() must be called to flush the final block through the BIO. If it is not
then the final block will fail a subsequent decrypt.
When decrypting an error on the final block is signalled by a zero return value from the read
operation. A successful decrypt followed by EOF will also return zero for the final read.
BIO_get_cipher_status() should be called to determine if the decrypt was successful.
As always, if BIO_gets() or BIO_puts() support is needed then it can be achieved by preceding the
cipher BIO with a buffering BIO.
RETURN VALUES
BIO_f_cipher() returns the cipher BIO method.
BIO_set_cipher() does not return a value.
BIO_get_cipher_status() returns 1 for a successful decrypt and 0 for failure.
BIO_get_cipher_ctx() currently always returns 1.
EXAMPLES
TBA
SEE ALSO
TBA
0.9.7l 2003-02-27 BIO_f_cipher(3)
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