BIO_f_cipher(3)

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

# LIBRARY

libcrypto, -lcrypto

# 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

2009-07-19 | 1.0.2k