Edit File: BIO_f_cipher.3
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Always turn off hyphenation; it makes .\" way too many mistakes in technical documents. .if n .ad l .nh .SH "NAME" BIO_f_cipher, BIO_set_cipher, BIO_get_cipher_status, BIO_get_cipher_ctx \- cipher BIO filter .SH "SYNOPSIS" .IX Header "SYNOPSIS" .Vb 2 \& #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) .Ve .SH "DESCRIPTION" .IX Header "DESCRIPTION" \&\fBBIO_f_cipher()\fR returns the cipher \s-1BIO\s0 method. This is a filter \&\s-1BIO\s0 that encrypts any data written through it, and decrypts any data read from it. It is a \s-1BIO\s0 wrapper for the cipher routines \&\fBEVP_CipherInit()\fR, \fBEVP_CipherUpdate()\fR and \fBEVP_CipherFinal()\fR. .PP Cipher BIOs do not support \fBBIO_gets()\fR or \fBBIO_puts()\fR. .PP \&\fBBIO_flush()\fR on an encryption \s-1BIO\s0 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 \s-1BIO.\s0 .PP \&\fBBIO_set_cipher()\fR sets the cipher of \s-1BIO\s0 \fBb\fR to \fBcipher\fR using key \fBkey\fR and \s-1IV\s0 \fBiv\fR. \fBenc\fR should be set to 1 for encryption and zero for decryption. .PP When reading from an encryption \s-1BIO\s0 the final block is automatically decrypted and checked when \s-1EOF\s0 is detected. \fBBIO_get_cipher_status()\fR is a \fBBIO_ctrl()\fR macro which can be called to determine whether the decryption operation was successful. .PP \&\fBBIO_get_cipher_ctx()\fR is a \fBBIO_ctrl()\fR macro which retrieves the internal \&\s-1BIO\s0 cipher context. The retrieved context can be used in conjunction with the standard cipher routines to set it up. This is useful when \&\fBBIO_set_cipher()\fR is not flexible enough for the applications needs. .SH "NOTES" .IX Header "NOTES" When encrypting \fBBIO_flush()\fR \fBmust\fR be called to flush the final block through the \s-1BIO.\s0 If it is not then the final block will fail a subsequent decrypt. .PP When decrypting an error on the final block is signalled by a zero return value from the read operation. A successful decrypt followed by \s-1EOF\s0 will also return zero for the final read. \fBBIO_get_cipher_status()\fR should be called to determine if the decrypt was successful. .PP As always, if \fBBIO_gets()\fR or \fBBIO_puts()\fR support is needed then it can be achieved by preceding the cipher \s-1BIO\s0 with a buffering \s-1BIO.\s0 .SH "RETURN VALUES" .IX Header "RETURN VALUES" \&\fBBIO_f_cipher()\fR returns the cipher \s-1BIO\s0 method. .PP \&\fBBIO_set_cipher()\fR does not return a value. .PP \&\fBBIO_get_cipher_status()\fR returns 1 for a successful decrypt and 0 for failure. .PP \&\fBBIO_get_cipher_ctx()\fR currently always returns 1. .SH "EXAMPLES" .IX Header "EXAMPLES" \&\s-1TBA\s0 .SH "SEE ALSO" .IX Header "SEE ALSO" \&\s-1TBA\s0