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131 .IX Title "BIO_f_cipher 3"
132 .TH BIO_f_cipher 3 "2017-12-07" "1.0.2n" "OpenSSL"
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138 BIO_f_cipher, BIO_set_cipher, BIO_get_cipher_status, BIO_get_cipher_ctx \- cipher BIO filter
140 .IX Header "SYNOPSIS"
142 \& #include <openssl/bio.h>
143 \& #include <openssl/evp.h>
145 \& BIO_METHOD * BIO_f_cipher(void);
146 \& void BIO_set_cipher(BIO *b,const EVP_CIPHER *cipher,
147 \& unsigned char *key, unsigned char *iv, int enc);
148 \& int BIO_get_cipher_status(BIO *b)
149 \& int BIO_get_cipher_ctx(BIO *b, EVP_CIPHER_CTX **pctx)
152 .IX Header "DESCRIPTION"
153 \&\fIBIO_f_cipher()\fR returns the cipher \s-1BIO\s0 method. This is a filter
154 \&\s-1BIO\s0 that encrypts any data written through it, and decrypts any data
155 read from it. It is a \s-1BIO\s0 wrapper for the cipher routines
156 \&\fIEVP_CipherInit()\fR, \fIEVP_CipherUpdate()\fR and \fIEVP_CipherFinal()\fR.
158 Cipher BIOs do not support \fIBIO_gets()\fR or \fIBIO_puts()\fR.
160 \&\fIBIO_flush()\fR on an encryption \s-1BIO\s0 that is being written through is
161 used to signal that no more data is to be encrypted: this is used
162 to flush and possibly pad the final block through the \s-1BIO.\s0
164 \&\fIBIO_set_cipher()\fR sets the cipher of \s-1BIO \s0\fBb\fR to \fBcipher\fR using key \fBkey\fR
165 and \s-1IV \s0\fBiv\fR. \fBenc\fR should be set to 1 for encryption and zero for
168 When reading from an encryption \s-1BIO\s0 the final block is automatically
169 decrypted and checked when \s-1EOF\s0 is detected. \fIBIO_get_cipher_status()\fR
170 is a \fIBIO_ctrl()\fR macro which can be called to determine whether the
171 decryption operation was successful.
173 \&\fIBIO_get_cipher_ctx()\fR is a \fIBIO_ctrl()\fR macro which retrieves the internal
174 \&\s-1BIO\s0 cipher context. The retrieved context can be used in conjunction
175 with the standard cipher routines to set it up. This is useful when
176 \&\fIBIO_set_cipher()\fR is not flexible enough for the applications needs.
179 When encrypting \fIBIO_flush()\fR \fBmust\fR be called to flush the final block
180 through the \s-1BIO.\s0 If it is not then the final block will fail a subsequent
183 When decrypting an error on the final block is signalled by a zero
184 return value from the read operation. A successful decrypt followed
185 by \s-1EOF\s0 will also return zero for the final read. \fIBIO_get_cipher_status()\fR
186 should be called to determine if the decrypt was successful.
188 As always, if \fIBIO_gets()\fR or \fIBIO_puts()\fR support is needed then it can
189 be achieved by preceding the cipher \s-1BIO\s0 with a buffering \s-1BIO.\s0
191 .IX Header "RETURN VALUES"
192 \&\fIBIO_f_cipher()\fR returns the cipher \s-1BIO\s0 method.
194 \&\fIBIO_set_cipher()\fR does not return a value.
196 \&\fIBIO_get_cipher_status()\fR returns 1 for a successful decrypt and 0
199 \&\fIBIO_get_cipher_ctx()\fR currently always returns 1.
201 .IX Header "EXAMPLES"
204 .IX Header "SEE ALSO"