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BIO(3)		      DragonFly Library Functions Manual		BIO(3)


NAME

     BIO -- I/O abstraction


SYNOPSIS

     #include <openssl/bio.h>


DESCRIPTION

     A BIO is an I/O abstraction, it hides many of the underlying I/O details
     from an application.  If an application uses a BIO for its I/O, it can
     transparently handle SSL connections, unencrypted network connections and
     file I/O.

     There are two types of BIO, a source/sink BIO and a filter BIO.

     As its name implies, a source/sink BIO is a source and/or sink of data,
     examples include a socket BIO and a file BIO.

     A filter BIO takes data from one BIO and passes it through to another, or
     to the application.  The data may be left unmodified (for example a mes-
     sage digest BIO) or translated (for example an encryption BIO).  The
     effect of a filter BIO may change according to the I/O operation it is
     performing: for example an encryption BIO will encrypt data if it is
     being written to and decrypt data if it is being read from.

     BIOs can be joined together to form a chain (a single BIO is a chain with
     one component).  A chain normally consist of one source/sink BIO and one
     or more filter BIOs.  Data read from or written to the first BIO then
     traverses the chain to the end (normally a source/sink BIO).


SEE ALSO

     BIO_ctrl(3), BIO_f_base64(3), BIO_f_buffer(3), BIO_f_cipher(3),
     BIO_f_md(3), BIO_f_null(3), BIO_f_ssl(3), BIO_find_type(3), BIO_new(3),
     BIO_new_bio_pair(3), BIO_push(3), BIO_read(3), BIO_s_accept(3),
     BIO_s_bio(3), BIO_s_connect(3), BIO_s_fd(3), BIO_s_file(3), BIO_s_mem(3),
     BIO_s_null(3), BIO_s_socket(3), BIO_set_callback(3), BIO_should_retry(3)

DragonFly 4.7			 July 17, 2014			 DragonFly 4.7
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


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

1.0.2h                            2016-05-03                   BIO_f_cipher(3)

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