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126 .IX Title "BIO_f_cipher 3"
127 .TH BIO_f_cipher 3 "2012-05-10" "1.0.1c" "OpenSSL"
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133 BIO_f_cipher, BIO_set_cipher, BIO_get_cipher_status, BIO_get_cipher_ctx \- cipher BIO filter
135 .IX Header "SYNOPSIS"
137 \& #include <openssl/bio.h>
138 \& #include <openssl/evp.h>
140 \& BIO_METHOD * BIO_f_cipher(void);
141 \& void BIO_set_cipher(BIO *b,const EVP_CIPHER *cipher,
142 \& unsigned char *key, unsigned char *iv, int enc);
143 \& int BIO_get_cipher_status(BIO *b)
144 \& int BIO_get_cipher_ctx(BIO *b, EVP_CIPHER_CTX **pctx)
147 .IX Header "DESCRIPTION"
148 \&\fIBIO_f_cipher()\fR returns the cipher \s-1BIO\s0 method. This is a filter
149 \&\s-1BIO\s0 that encrypts any data written through it, and decrypts any data
150 read from it. It is a \s-1BIO\s0 wrapper for the cipher routines
151 \&\fIEVP_CipherInit()\fR, \fIEVP_CipherUpdate()\fR and \fIEVP_CipherFinal()\fR.
153 Cipher BIOs do not support \fIBIO_gets()\fR or \fIBIO_puts()\fR.
155 \&\fIBIO_flush()\fR on an encryption \s-1BIO\s0 that is being written through is
156 used to signal that no more data is to be encrypted: this is used
157 to flush and possibly pad the final block through the \s-1BIO\s0.
159 \&\fIBIO_set_cipher()\fR sets the cipher of \s-1BIO\s0 \fBb\fR to \fBcipher\fR using key \fBkey\fR
160 and \s-1IV\s0 \fBiv\fR. \fBenc\fR should be set to 1 for encryption and zero for
163 When reading from an encryption \s-1BIO\s0 the final block is automatically
164 decrypted and checked when \s-1EOF\s0 is detected. \fIBIO_get_cipher_status()\fR
165 is a \fIBIO_ctrl()\fR macro which can be called to determine whether the
166 decryption operation was successful.
168 \&\fIBIO_get_cipher_ctx()\fR is a \fIBIO_ctrl()\fR macro which retrieves the internal
169 \&\s-1BIO\s0 cipher context. The retrieved context can be used in conjunction
170 with the standard cipher routines to set it up. This is useful when
171 \&\fIBIO_set_cipher()\fR is not flexible enough for the applications needs.
174 When encrypting \fIBIO_flush()\fR \fBmust\fR be called to flush the final block
175 through the \s-1BIO\s0. If it is not then the final block will fail a subsequent
178 When decrypting an error on the final block is signalled by a zero
179 return value from the read operation. A successful decrypt followed
180 by \s-1EOF\s0 will also return zero for the final read. \fIBIO_get_cipher_status()\fR
181 should be called to determine if the decrypt was successful.
183 As always, if \fIBIO_gets()\fR or \fIBIO_puts()\fR support is needed then it can
184 be achieved by preceding the cipher \s-1BIO\s0 with a buffering \s-1BIO\s0.
186 .IX Header "RETURN VALUES"
187 \&\fIBIO_f_cipher()\fR returns the cipher \s-1BIO\s0 method.
189 \&\fIBIO_set_cipher()\fR does not return a value.
191 \&\fIBIO_get_cipher_status()\fR returns 1 for a successful decrypt and 0
194 \&\fIBIO_get_cipher_ctx()\fR currently always returns 1.
196 .IX Header "EXAMPLES"
199 .IX Header "SEE ALSO"