1=pod 2 3=head1 NAME 4 5BIO_f_cipher, BIO_set_cipher, BIO_get_cipher_status, BIO_get_cipher_ctx - cipher BIO filter 6 7=head1 SYNOPSIS 8 9 #include <openssl/bio.h> 10 #include <openssl/evp.h> 11 12 BIO_METHOD * BIO_f_cipher(void); 13 void BIO_set_cipher(BIO *b,const EVP_CIPHER *cipher, 14 unsigned char *key, unsigned char *iv, int enc); 15 int BIO_get_cipher_status(BIO *b) 16 int BIO_get_cipher_ctx(BIO *b, EVP_CIPHER_CTX **pctx) 17 18=head1 DESCRIPTION 19 20BIO_f_cipher() returns the cipher BIO method. This is a filter 21BIO that encrypts any data written through it, and decrypts any data 22read from it. It is a BIO wrapper for the cipher routines 23EVP_CipherInit(), EVP_CipherUpdate() and EVP_CipherFinal(). 24 25Cipher BIOs do not support BIO_gets() or BIO_puts(). 26 27BIO_flush() on an encryption BIO that is being written through is 28used to signal that no more data is to be encrypted: this is used 29to flush and possibly pad the final block through the BIO. 30 31BIO_set_cipher() sets the cipher of BIO B<b> to B<cipher> using key B<key> 32and IV B<iv>. B<enc> should be set to 1 for encryption and zero for 33decryption. 34 35When reading from an encryption BIO the final block is automatically 36decrypted and checked when EOF is detected. BIO_get_cipher_status() 37is a BIO_ctrl() macro which can be called to determine whether the 38decryption operation was successful. 39 40BIO_get_cipher_ctx() is a BIO_ctrl() macro which retrieves the internal 41BIO cipher context. The retrieved context can be used in conjunction 42with the standard cipher routines to set it up. This is useful when 43BIO_set_cipher() is not flexible enough for the applications needs. 44 45=head1 NOTES 46 47When encrypting BIO_flush() B<must> be called to flush the final block 48through the BIO. If it is not then the final block will fail a subsequent 49decrypt. 50 51When decrypting an error on the final block is signalled by a zero 52return value from the read operation. A successful decrypt followed 53by EOF will also return zero for the final read. BIO_get_cipher_status() 54should be called to determine if the decrypt was successful. 55 56As always, if BIO_gets() or BIO_puts() support is needed then it can 57be achieved by preceding the cipher BIO with a buffering BIO. 58 59=head1 RETURN VALUES 60 61BIO_f_cipher() returns the cipher BIO method. 62 63BIO_set_cipher() does not return a value. 64 65BIO_get_cipher_status() returns 1 for a successful decrypt and 0 66for failure. 67 68BIO_get_cipher_ctx() currently always returns 1. 69 70=head1 EXAMPLES 71 72TBA 73 74=head1 SEE ALSO 75 76TBA 77