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.
