cipher BIO filter
const BIO_METHOD *
const EVP_CIPHER *cipher, unsigned
char *key, unsigned char *iv,
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
Cipher BIOs do not support BIO_gets(3) or BIO_puts(3).
BIO_flush(3) 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.
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.
is a BIO_ctrl(3) macro which can be called to determine whether the
decryption operation was successful.
is a BIO_ctrl(3) 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
When a chain containing a cipher BIO is copied with BIO_dup_chain(3), the cipher context is automatically copied from the existing BIO object to the new one and the init flag that can be retrieved with BIO_get_init(3) is set to 1.
When encrypting, BIO_flush(3) 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.
should be called to determine if the decrypt was successful.
As always, if BIO_gets(3) or BIO_puts(3) support is needed, then it can be achieved by preceding the cipher BIO with a buffering BIO.
BIO_f_cipher() returns the cipher BIO
BIO_set_cipher() returns 1 on success and 0
BIO_get_cipher_status() returns 1 for a
successful decrypt and 0 for failure.
BIO_get_cipher_ctx() currently always
BIO_get_cipher_status() first appeared in SSLeay
0.6.5 and have been available since OpenBSD 2.4.
BIO_get_cipher_ctx() first appeared in
SSLeay 0.9.1 and has been available since OpenBSD