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BIO_f_cipher(3)                     OpenSSL                    BIO_f_cipher(3)


BIO_f_cipher, BIO_set_cipher, BIO_get_cipher_status, BIO_get_cipher_ctx - cipher BIO filter


#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)


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.


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.


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.




TBA 1.0.2h 2016-05-03 BIO_f_cipher(3)

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