334 lines
10 KiB
Groff
334 lines
10 KiB
Groff
.\" $OpenBSD: EVP_EncodeInit.3,v 1.7 2019/06/06 01:06:58 schwarze Exp $
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.\" full merge up to: OpenSSL f430ba31 Jun 19 19:39:01 2016 +0200
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.\" selective merge up to: OpenSSL e9b77246 Jan 20 19:58:49 2017 +0100
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.\"
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.\" This file was written by Matt Caswell <matt@openssl.org>.
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.\" Copyright (c) 2016 The OpenSSL Project. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\"
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\"
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in
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.\" the documentation and/or other materials provided with the
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.\" distribution.
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.\"
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.\" 3. All advertising materials mentioning features or use of this
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.\" software must display the following acknowledgment:
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.\" "This product includes software developed by the OpenSSL Project
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.\" for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
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.\"
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.\" 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
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.\" endorse or promote products derived from this software without
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.\" prior written permission. For written permission, please contact
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.\" openssl-core@openssl.org.
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.\"
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.\" 5. Products derived from this software may not be called "OpenSSL"
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.\" nor may "OpenSSL" appear in their names without prior written
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.\" permission of the OpenSSL Project.
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.\"
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.\" 6. Redistributions of any form whatsoever must retain the following
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.\" acknowledgment:
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.\" "This product includes software developed by the OpenSSL Project
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.\" for use in the OpenSSL Toolkit (http://www.openssl.org/)"
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
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.\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
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.\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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.\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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.\" OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd $Mdocdate: June 6 2019 $
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.Dt EVP_ENCODEINIT 3
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.Os
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.Sh NAME
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.Nm EVP_ENCODE_CTX_new ,
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.Nm EVP_ENCODE_CTX_free ,
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.Nm EVP_EncodeInit ,
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.Nm EVP_EncodeUpdate ,
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.Nm EVP_EncodeFinal ,
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.Nm EVP_EncodeBlock ,
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.Nm EVP_DecodeInit ,
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.Nm EVP_DecodeUpdate ,
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.Nm EVP_DecodeFinal ,
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.Nm EVP_DecodeBlock
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.Nd EVP base64 encode/decode routines
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.Sh SYNOPSIS
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.In openssl/evp.h
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.Ft EVP_ENCODE_CTX *
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.Fn EVP_ENCODE_CTX_new void
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.Ft void
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.Fo EVP_ENCODE_CTX_free
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.Fa "EVP_ENCODE_CTX *ctx"
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.Fc
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.Ft void
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.Fo EVP_EncodeInit
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.Fa "EVP_ENCODE_CTX *ctx"
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.Fc
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.Ft int
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.Fo EVP_EncodeUpdate
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.Fa "EVP_ENCODE_CTX *ctx"
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.Fa "unsigned char *out"
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.Fa "int *outl"
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.Fa "const unsigned char *in"
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.Fa "int inl"
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.Fc
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.Ft void
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.Fo EVP_EncodeFinal
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.Fa "EVP_ENCODE_CTX *ctx"
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.Fa "unsigned char *out"
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.Fa "int *outl"
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.Fc
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.Ft int
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.Fo EVP_EncodeBlock
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.Fa "unsigned char *t"
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.Fa "const unsigned char *f"
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.Fa "int n"
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.Fc
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.Ft void
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.Fo EVP_DecodeInit
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.Fa "EVP_ENCODE_CTX *ctx"
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.Fc
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.Ft int
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.Fo EVP_DecodeUpdate
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.Fa "EVP_ENCODE_CTX *ctx"
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.Fa "unsigned char *out"
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.Fa "int *outl"
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.Fa "const unsigned char *in"
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.Fa "int inl"
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.Fc
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.Ft int
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.Fo EVP_DecodeFinal
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.Fa "EVP_ENCODE_CTX *ctx"
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.Fa "unsigned char *out"
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.Fa "int *outl"
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.Fc
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.Ft int
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.Fo EVP_DecodeBlock
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.Fa "unsigned char *t"
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.Fa "const unsigned char *f"
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.Fa "int n"
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.Fc
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.Sh DESCRIPTION
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The EVP encode routines provide a high level interface to base64
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encoding and decoding.
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Base64 encoding converts binary data into a printable form that uses
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the characters A-Z, a-z, 0-9, "+" and "/" to represent the data.
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For every 3 bytes of binary data provided, 4 bytes of base64-encoded
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data will be produced, plus some occasional newlines.
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If the input data length is not a multiple of 3, then the output data
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will be padded at the end using the "=" character.
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.Pp
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.Fn EVP_ENCODE_CTX_new
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allocates, initializes and returns a context to be used for the encode
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and decode functions.
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.Pp
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.Fn EVP_ENCODE_CTX_free
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frees
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.Fa ctx .
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.Pp
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Encoding of binary data is performed in blocks of 48 input bytes (or
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less for the final block).
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For each 48-byte input block encoded, 64 bytes of base64 data is output,
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plus an additional newline character, i.e. 65 bytes in total.
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The final block, which may be less than 48 bytes, will output 4 bytes
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for every 3 bytes of input.
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If the data length is not divisible by 3, then a full 4 bytes is still
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output for the final 1 or 2 bytes of input.
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Similarly a newline character will also be output.
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.Pp
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.Fn EVP_EncodeInit
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initialises
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.Fa ctx
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for the start of a new encoding operation.
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.Pp
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.Fn EVP_EncodeUpdate
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encodes
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.Fa inl
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bytes of data found in the buffer pointed to by
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.Fa in .
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The output is stored in the buffer
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.Fa out
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and the number of bytes output is stored in
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.Pf * Fa outl .
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It is the caller's responsibility to ensure that the buffer at
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.Fa out
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is sufficiently large to accommodate the output data.
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Only full blocks of data (48 bytes) will be immediately processed and
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output by this function.
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Any remainder is held in the
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.Fa ctx
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object and will be processed by a subsequent call to
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.Fn EVP_EncodeUpdate
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or
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.Fn EVP_EncodeFinal .
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To calculate the required size of the output buffer, add together the
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value of
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.Fa inl
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with the amount of unprocessed data held in
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.Fa ctx
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and divide the result by 48 (ignore any remainder).
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This gives the number of blocks of data that will be processed.
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Ensure the output buffer contains 65 bytes of storage for each block,
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plus an additional byte for a NUL terminator.
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.Fn EVP_EncodeUpdate
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may be called repeatedly to process large amounts of input data.
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In the event of an error ,
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.Fn EVP_EncodeUpdate
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will set
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.Pf * Fa outl
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to 0 and return 0.
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On success 1 will be returned.
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.Pp
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.Fn EVP_EncodeFinal
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must be called at the end of an encoding operation.
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It will process any partial block of data remaining in the
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.Fa ctx
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object.
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The output data will be stored in
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.Fa out
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and the length of the data written will be stored in
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.Pf * Fa outl .
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It is the caller's responsibility to ensure that
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.Fa out
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is sufficiently large to accommodate the output data, which will
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never be more than 65 bytes plus an additional NUL terminator, i.e.
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66 bytes in total.
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.Pp
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.Fn EVP_EncodeBlock
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encodes a full block of input data in
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.Fa f
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and of length
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.Fa n
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and stores it in
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.Fa t .
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For every 3 bytes of input provided, 4 bytes of output data will be
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produced.
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If
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.Sy n
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is not divisible by 3, then the block is encoded as a final block
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of data and the output is padded such that it is always divisible
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by 4.
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Additionally a NUL terminator character will be added.
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For example, if 16 bytes of input data are provided, then 24 bytes
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of encoded data is created plus 1 byte for a NUL terminator,
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i.e. 25 bytes in total.
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The length of the data generated
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.Em without
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the NUL terminator is returned from the function.
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.Pp
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.Fn EVP_DecodeInit
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initialises
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.Fa ctx
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for the start of a new decoding operation.
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.Pp
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.Fn EVP_DecodeUpdate
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decodes
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.Fa inl
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characters of data found in the buffer pointed to by
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.Fa in .
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The output is stored in the buffer
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.Fa out
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and the number of bytes output is stored in
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.Pf * Fa outl .
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It is the caller's responsibility to ensure that the buffer at
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.Fa out
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is sufficiently large to accommodate the output data.
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This function will attempt to decode as much data as possible in 4-byte
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chunks.
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Any whitespace, newline or carriage return characters are ignored.
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Any partial chunk of unprocessed data (1, 2 or 3 bytes) that remains at
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the end will be held in the
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.Fa ctx
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object and processed by a subsequent call to
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.Fn EVP_DecodeUpdate .
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If any illegal base64 characters are encountered or if the base64
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padding character "=" is encountered in the middle of the data,
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then the function returns -1 to indicate an error.
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A return value of 0 or 1 indicates successful processing of the data.
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A return value of 0 additionally indicates that the last input data
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characters processed included the base64 padding character "=" and
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therefore no more non-padding character data is expected to be
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processed.
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For every 4 valid base64 bytes processed \(em ignoring whitespace,
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carriage returns and line feeds \(em 3 bytes of binary output data
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will be produced, or less at the end of the data where the padding
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character "=" has been used.
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.Pp
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.Fn EVP_DecodeFinal
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must be called at the end of a decoding operation.
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If there is any unprocessed data still in
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.Fa ctx ,
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then the input data must not have been a multiple of 4 and therefore an
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error has occurred.
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The function will return -1 in this case.
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Otherwise the function returns 1 on success.
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.Pp
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.Fn EVP_DecodeBlock
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will decode the block of
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.Fa n
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characters of base64 data contained in
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.Fa f
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and store the result in
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.Fa t .
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Any leading whitespace will be trimmed as will any trailing whitespace,
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newlines, carriage returns or EOF characters.
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After such trimming the length of the data in
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.Fa f
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must be divisible by 4.
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For every 4 input bytes, exactly 3 output bytes will be produced.
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The output will be padded with 0 bits if necessary to ensure that the
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output is always 3 bytes for every 4 input bytes.
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This function will return the length of the data decoded or -1 on error.
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.Sh RETURN VALUES
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.Fn EVP_ENCODE_CTX_new
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returns a pointer to the newly allocated
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.Vt EVP_ENCODE_CTX
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object or
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.Dv NULL
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on error.
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.Pp
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.Fn EVP_EncodeUpdate
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returns 0 on error or 1 on success.
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.Pp
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.Fn EVP_EncodeBlock
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returns the number of bytes encoded excluding the NUL terminator.
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.Pp
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.Fn EVP_DecodeUpdate
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returns -1 on error and 0 or 1 on success.
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If 0 is returned, then no more non-padding base64 characters are
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expected.
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.Pp
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.Fn EVP_DecodeFinal
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returns -1 on error or 1 on success.
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.Pp
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.Fn EVP_DecodeBlock
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returns the length of the data decoded or -1 on error.
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.Sh SEE ALSO
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.Xr BIO_f_base64 3 ,
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.Xr evp 3
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.Sh HISTORY
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The
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.Fn EVP_Encode*
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and
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.Fn EVP_Decode*
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functions first appeared in SSLeay 0.5.1
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and have been available since
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.Ox 2.4 .
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.Pp
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.Fn EVP_ENCODE_CTX_new
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and
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.Fn EVP_ENCODE_CTX_free
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first appeared in OpenSSL 1.1.0 and have been available since
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.Ox 6.5 .
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