1=pod 2 3=head1 NAME 4 5EVP_ENCODE_CTX_new, EVP_ENCODE_CTX_free, EVP_ENCODE_CTX_copy, 6EVP_ENCODE_CTX_num, EVP_EncodeInit, EVP_EncodeUpdate, EVP_EncodeFinal, 7EVP_EncodeBlock, EVP_DecodeInit, EVP_DecodeUpdate, EVP_DecodeFinal, 8EVP_DecodeBlock - EVP base 64 encode/decode routines 9 10=head1 SYNOPSIS 11 12 #include <openssl/evp.h> 13 14 EVP_ENCODE_CTX *EVP_ENCODE_CTX_new(void); 15 void EVP_ENCODE_CTX_free(EVP_ENCODE_CTX *ctx); 16 int EVP_ENCODE_CTX_copy(EVP_ENCODE_CTX *dctx, EVP_ENCODE_CTX *sctx); 17 int EVP_ENCODE_CTX_num(EVP_ENCODE_CTX *ctx); 18 void EVP_EncodeInit(EVP_ENCODE_CTX *ctx); 19 int EVP_EncodeUpdate(EVP_ENCODE_CTX *ctx, unsigned char *out, int *outl, 20 const unsigned char *in, int inl); 21 void EVP_EncodeFinal(EVP_ENCODE_CTX *ctx, unsigned char *out, int *outl); 22 int EVP_EncodeBlock(unsigned char *t, const unsigned char *f, int n); 23 24 void EVP_DecodeInit(EVP_ENCODE_CTX *ctx); 25 int EVP_DecodeUpdate(EVP_ENCODE_CTX *ctx, unsigned char *out, int *outl, 26 const unsigned char *in, int inl); 27 int EVP_DecodeFinal(EVP_ENCODE_CTX *ctx, unsigned char *out, int *outl); 28 int EVP_DecodeBlock(unsigned char *t, const unsigned char *f, int n); 29 30=head1 DESCRIPTION 31 32The EVP encode routines provide a high-level interface to base 64 encoding and 33decoding. Base 64 encoding converts binary data into a printable form that uses 34the characters A-Z, a-z, 0-9, "+" and "/" to represent the data. For every 3 35bytes of binary data provided 4 bytes of base 64 encoded data will be produced 36plus some occasional newlines (see below). If the input data length is not a 37multiple of 3 then the output data will be padded at the end using the "=" 38character. 39 40EVP_ENCODE_CTX_new() allocates, initializes and returns a context to be used for 41the encode/decode functions. 42 43EVP_ENCODE_CTX_free() cleans up an encode/decode context B<ctx> and frees up the 44space allocated to it. 45 46Encoding of binary data is performed in blocks of 48 input bytes (or less for 47the final block). For each 48 byte input block encoded 64 bytes of base 64 data 48is output plus an additional newline character (i.e. 65 bytes in total). The 49final block (which may be less than 48 bytes) will output 4 bytes for every 3 50bytes of input. If the data length is not divisible by 3 then a full 4 bytes is 51still output for the final 1 or 2 bytes of input. Similarly a newline character 52will also be output. 53 54EVP_EncodeInit() initialises B<ctx> for the start of a new encoding operation. 55 56EVP_EncodeUpdate() encode B<inl> bytes of data found in the buffer pointed to by 57B<in>. The output is stored in the buffer B<out> and the number of bytes output 58is stored in B<*outl>. It is the caller's responsibility to ensure that the 59buffer at B<out> is sufficiently large to accommodate the output data. Only full 60blocks of data (48 bytes) will be immediately processed and output by this 61function. Any remainder is held in the B<ctx> object and will be processed by a 62subsequent call to EVP_EncodeUpdate() or EVP_EncodeFinal(). To calculate the 63required size of the output buffer add together the value of B<inl> with the 64amount of unprocessed data held in B<ctx> and divide the result by 48 (ignore 65any remainder). This gives the number of blocks of data that will be processed. 66Ensure the output buffer contains 65 bytes of storage for each block, plus an 67additional byte for a NUL terminator. EVP_EncodeUpdate() may be called 68repeatedly to process large amounts of input data. In the event of an error 69EVP_EncodeUpdate() will set B<*outl> to 0 and return 0. On success 1 will be 70returned. 71 72EVP_EncodeFinal() must be called at the end of an encoding operation. It will 73process any partial block of data remaining in the B<ctx> object. The output 74data will be stored in B<out> and the length of the data written will be stored 75in B<*outl>. It is the caller's responsibility to ensure that B<out> is 76sufficiently large to accommodate the output data which will never be more than 7765 bytes plus an additional NUL terminator (i.e. 66 bytes in total). 78 79EVP_ENCODE_CTX_copy() can be used to copy a context B<sctx> to a context 80B<dctx>. B<dctx> must be initialized before calling this function. 81 82EVP_ENCODE_CTX_num() will return the number of as yet unprocessed bytes still to 83be encoded or decoded that are pending in the B<ctx> object. 84 85EVP_EncodeBlock() encodes a full block of input data in B<f> and of length 86B<n> and stores it in B<t>. For every 3 bytes of input provided 4 bytes of 87output data will be produced. If B<n> is not divisible by 3 then the block is 88encoded as a final block of data and the output is padded such that it is always 89divisible by 4. Additionally a NUL terminator character will be added. For 90example if 16 bytes of input data is provided then 24 bytes of encoded data is 91created plus 1 byte for a NUL terminator (i.e. 25 bytes in total). The length of 92the data generated I<without> the NUL terminator is returned from the function. 93 94EVP_DecodeInit() initialises B<ctx> for the start of a new decoding operation. 95 96EVP_DecodeUpdate() decodes B<inl> characters of data found in the buffer pointed 97to by B<in>. The output is stored in the buffer B<out> and the number of bytes 98output is stored in B<*outl>. It is the caller's responsibility to ensure that 99the buffer at B<out> is sufficiently large to accommodate the output data. This 100function will attempt to decode as much data as possible in 4 byte chunks. Any 101whitespace, newline or carriage return characters are ignored. Any partial chunk 102of unprocessed data (1, 2 or 3 bytes) that remains at the end will be held in 103the B<ctx> object and processed by a subsequent call to EVP_DecodeUpdate(). If 104any illegal base 64 characters are encountered or if the base 64 padding 105character "=" is encountered in the middle of the data then the function returns 106-1 to indicate an error. A return value of 0 or 1 indicates successful 107processing of the data. A return value of 0 additionally indicates that the last 108input data characters processed included the base 64 padding character "=" and 109therefore no more non-padding character data is expected to be processed. For 110every 4 valid base 64 bytes processed (ignoring whitespace, carriage returns and 111line feeds), 3 bytes of binary output data will be produced (or less at the end 112of the data where the padding character "=" has been used). 113 114EVP_DecodeFinal() must be called at the end of a decoding operation. If there 115is any unprocessed data still in B<ctx> then the input data must not have been 116a multiple of 4 and therefore an error has occurred. The function will return -1 117in this case. Otherwise the function returns 1 on success. 118 119EVP_DecodeBlock() will decode the block of B<n> characters of base 64 data 120contained in B<f> and store the result in B<t>. Any leading whitespace will be 121trimmed as will any trailing whitespace, newlines, carriage returns or EOF 122characters. After such trimming the length of the data in B<f> must be divisible 123by 4. For every 4 input bytes exactly 3 output bytes will be produced. The 124output will be padded with 0 bits if necessary to ensure that the output is 125always 3 bytes for every 4 input bytes. This function will return the length of 126the data decoded or -1 on error. 127 128=head1 RETURN VALUES 129 130EVP_ENCODE_CTX_new() returns a pointer to the newly allocated EVP_ENCODE_CTX 131object or NULL on error. 132 133EVP_ENCODE_CTX_num() returns the number of bytes pending encoding or decoding in 134B<ctx>. 135 136EVP_EncodeUpdate() returns 0 on error or 1 on success. 137 138EVP_EncodeBlock() returns the number of bytes encoded excluding the NUL 139terminator. 140 141EVP_DecodeUpdate() returns -1 on error and 0 or 1 on success. If 0 is returned 142then no more non-padding base 64 characters are expected. 143 144EVP_DecodeFinal() returns -1 on error or 1 on success. 145 146EVP_DecodeBlock() returns the length of the data decoded or -1 on error. 147 148=head1 SEE ALSO 149 150L<evp(7)> 151 152=head1 COPYRIGHT 153 154Copyright 2016-2020 The OpenSSL Project Authors. All Rights Reserved. 155 156Licensed under the Apache License 2.0 (the "License"). You may not use 157this file except in compliance with the License. You can obtain a copy 158in the file LICENSE in the source distribution or at 159L<https://www.openssl.org/source/license.html>. 160 161=cut 162