BIO_f_cipher(3)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
The BIO_f_cipher() function 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 EVP_CipherInit(),
EVP_CipherUpdate(), and EVP_CipherFinal() cipher functions .
Cipher BIOs do not support BIO_gets() or BIO_puts().
The BIO_flush() function 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.
The BIO_set_cipher() function sets the cipher of BIO b to cipher using
key and iv. The 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. The BIO_get_cipher_status()
function is a BIO_ctrl() macro which can be called to determine whether
the decryption operation was successful.
The BIO_get_cipher_ctx() function 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 applica‐
tions needs.
NOTES
When encrypting, BIO_flush() must be called to flush the final block
through the BIO. Otherwise, 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. The BIO_get_cipher_sta‐
tus() function should be called to determine if the decrypt was suc‐
cessful.
If BIO_gets() or BIO_puts() support is needed then it can be achieved
by preceding the cipher BIO with a buffering BIO.
RETURN VALUESBIO_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() always returns 1.
SEE ALSO
TBA
BIO_f_cipher(3)
