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140 .IX Title "BIO_f_cipher 3"
141 .TH BIO_f_cipher 3 "0.9.7a" "2003-02-19" "OpenSSL"
144 BIO_f_cipher, BIO_set_cipher, BIO_get_cipher_status, BIO_get_cipher_ctx \- cipher \s-1BIO\s0 filter
146 .IX Header "SYNOPSIS"
148 \& #include <openssl/bio.h>
149 \& #include <openssl/evp.h>
152 \& BIO_METHOD * BIO_f_cipher(void);
153 \& void BIO_set_cipher(BIO *b,const EVP_CIPHER *cipher,
154 \& unsigned char *key, unsigned char *iv, int enc);
155 \& int BIO_get_cipher_status(BIO *b)
156 \& int BIO_get_cipher_ctx(BIO *b, EVP_CIPHER_CTX **pctx)
159 .IX Header "DESCRIPTION"
160 \&\fIBIO_f_cipher()\fR returns the cipher \s-1BIO\s0 method. This is a filter
161 \&\s-1BIO\s0 that encrypts any data written through it, and decrypts any data
162 read from it. It is a \s-1BIO\s0 wrapper for the cipher routines
163 \&\fIEVP_CipherInit()\fR, \fIEVP_CipherUpdate()\fR and \fIEVP_CipherFinal()\fR.
165 Cipher BIOs do not support \fIBIO_gets()\fR or \fIBIO_puts()\fR.
167 \&\fIBIO_flush()\fR on an encryption \s-1BIO\s0 that is being written through is
168 used to signal that no more data is to be encrypted: this is used
169 to flush and possibly pad the final block through the \s-1BIO\s0.
171 \&\fIBIO_set_cipher()\fR sets the cipher of \s-1BIO\s0 <b> to \fBcipher\fR using key \fBkey\fR
172 and \s-1IV\s0 \fBiv\fR. \fBenc\fR should be set to 1 for encryption and zero for
175 When reading from an encryption \s-1BIO\s0 the final block is automatically
176 decrypted and checked when \s-1EOF\s0 is detected. \fIBIO_get_cipher_status()\fR
177 is a \fIBIO_ctrl()\fR macro which can be called to determine whether the
178 decryption operation was successful.
180 \&\fIBIO_get_cipher_ctx()\fR is a \fIBIO_ctrl()\fR macro which retrieves the internal
181 \&\s-1BIO\s0 cipher context. The retrieved context can be used in conjunction
182 with the standard cipher routines to set it up. This is useful when
183 \&\fIBIO_set_cipher()\fR is not flexible enough for the applications needs.
186 When encrypting \fIBIO_flush()\fR \fBmust\fR be called to flush the final block
187 through the \s-1BIO\s0. If it is not then the final block will fail a subsequent
190 When decrypting an error on the final block is signalled by a zero
191 return value from the read operation. A successful decrypt followed
192 by \s-1EOF\s0 will also return zero for the final read. \fIBIO_get_cipher_status()\fR
193 should be called to determine if the decrypt was successful.
195 As always, if \fIBIO_gets()\fR or \fIBIO_puts()\fR support is needed then it can
196 be achieved by preceding the cipher \s-1BIO\s0 with a buffering \s-1BIO\s0.
198 .IX Header "RETURN VALUES"
199 \&\fIBIO_f_cipher()\fR returns the cipher \s-1BIO\s0 method.
201 \&\fIBIO_set_cipher()\fR does not return a value.
203 \&\fIBIO_get_cipher_status()\fR returns 1 for a successful decrypt and 0
206 \&\fIBIO_get_cipher_ctx()\fR currently always returns 1.
208 .IX Header "EXAMPLES"
211 .IX Header "SEE ALSO"