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