OpenGrok

$NetBSD: BIO_f_cipher.3,v 1.1.1.2 2023/04/18 14:19:12 christos Exp $

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Title "BIO_f_cipher 3" For nroff, turn off justification. Always turn off hyphenation; it makes
way too many mistakes in technical documents.
.nh BIO_f_cipher, BIO_set_cipher, BIO_get_cipher_status, BIO_get_cipher_ctx - cipher BIO filter libcrypto, -lcrypto Header "SYNOPSIS" .Vb 2 #include <openssl/bio.h> #include <openssl/evp.h> \& const 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 Header "DESCRIPTION" \fBBIO_f_cipher() 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(), EVP_CipherUpdate() and EVP_CipherFinal().

Cipher BIOs do not support BIO_gets() or BIO_puts().

\fBBIO_flush() 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

\fBBIO_set_cipher() sets the cipher of \s-1BIO\s0 b to cipher using key key and \s-1IV\s0 iv. enc should be set to 1 for encryption and zero for decryption.

When reading from an encryption \s-1BIO\s0 the final block is automatically decrypted and checked when \s-1EOF\s0 is detected. BIO_get_cipher_status() is a BIO_ctrl() macro which can be called to determine whether the decryption operation was successful.

\fBBIO_get_cipher_ctx() is a BIO_ctrl() 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() is not flexible enough for the applications needs.

Header "NOTES" When encrypting BIO_flush() must 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.

When decrypting an error on the final block is signaled 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. 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 \s-1BIO\s0 with a buffering \s-1BIO.\s0

Header "RETURN VALUES" \fBBIO_f_cipher() returns the cipher \s-1BIO\s0 method.

\fBBIO_set_cipher() does not return a value.

\fBBIO_get_cipher_status() returns 1 for a successful decrypt and 0 for failure.

\fBBIO_get_cipher_ctx() currently always returns 1.

Header "COPYRIGHT" Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the OpenSSL license (the \*(L"License\*(R"). You may not use this file except in compliance with the License. You can obtain a copy in the file \s-1LICENSE\s0 in the source distribution or at <https://www.openssl.org/source/license.html>.

Indexes created Wed Apr 22 00:22:44 UTC 2026