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d202a602 MC |
1 | =pod |
2 | ||
3 | =head1 NAME | |
4 | ||
c1054bb4 JZ |
5 | EVP_ENCODE_CTX_new, EVP_ENCODE_CTX_free, EVP_ENCODE_CTX_copy, |
6 | EVP_ENCODE_CTX_num, EVP_EncodeInit, EVP_EncodeUpdate, EVP_EncodeFinal, | |
7 | EVP_EncodeBlock, EVP_DecodeInit, EVP_DecodeUpdate, EVP_DecodeFinal, | |
8 | EVP_DecodeBlock - EVP base 64 encode/decode routines | |
d202a602 MC |
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); | |
c1054bb4 | 16 | int EVP_ENCODE_CTX_copy(EVP_ENCODE_CTX *dctx, EVP_ENCODE_CTX *sctx); |
d202a602 MC |
17 | int EVP_ENCODE_CTX_num(EVP_ENCODE_CTX *ctx); |
18 | void EVP_EncodeInit(EVP_ENCODE_CTX *ctx); | |
cf3404fc MC |
19 | int EVP_EncodeUpdate(EVP_ENCODE_CTX *ctx, unsigned char *out, int *outl, |
20 | const unsigned char *in, int inl); | |
d202a602 MC |
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 | |
28 | char *out, int *outl); | |
29 | int EVP_DecodeBlock(unsigned char *t, const unsigned char *f, int n); | |
30 | ||
31 | =head1 DESCRIPTION | |
32 | ||
33 | The EVP encode routines provide a high level interface to base 64 encoding and | |
34 | decoding. Base 64 encoding converts binary data into a printable form that uses | |
35 | the characters A-Z, a-z, 0-9, "+" and "/" to represent the data. For every 3 | |
36 | bytes of binary data provided 4 bytes of base 64 encoded data will be produced | |
37 | plus some occasional newlines (see below). If the input data length is not a | |
38 | multiple of 3 then the output data will be padded at the end using the "=" | |
39 | character. | |
40 | ||
41 | EVP_ENCODE_CTX_new() allocates, initializes and returns a context to be used for | |
42 | the encode/decode functions. | |
43 | ||
44 | EVP_ENCODE_CTX_free() cleans up an encode/decode context B<ctx> and frees up the | |
45 | space allocated to it. | |
46 | ||
47 | Encoding of binary data is performed in blocks of 48 input bytes (or less for | |
48 | the final block). For each 48 byte input block encoded 64 bytes of base 64 data | |
49 | is output plus an additional newline character (i.e. 65 bytes in total). The | |
50 | final block (which may be less than 48 bytes) will output 4 bytes for every 3 | |
51 | bytes of input. If the data length is not divisible by 3 then a full 4 bytes is | |
52 | still output for the final 1 or 2 bytes of input. Similarly a newline character | |
53 | will also be output. | |
54 | ||
55 | EVP_EncodeInit() initialises B<ctx> for the start of a new encoding operation. | |
56 | ||
57 | EVP_EncodeUpdate() encode B<inl> bytes of data found in the buffer pointed to by | |
58 | B<in>. The output is stored in the buffer B<out> and the number of bytes output | |
59 | is stored in B<*outl>. It is the caller's responsibility to ensure that the | |
60 | buffer at B<out> is sufficiently large to accommodate the output data. Only full | |
61 | blocks of data (48 bytes) will be immediately processed and output by this | |
62 | function. Any remainder is held in the B<ctx> object and will be processed by a | |
63 | subsequent call to EVP_EncodeUpdate() or EVP_EncodeFinal(). To calculate the | |
64 | required size of the output buffer add together the value of B<inl> with the | |
65 | amount of unprocessed data held in B<ctx> and divide the result by 48 (ignore | |
66 | any remainder). This gives the number of blocks of data that will be processed. | |
67 | Ensure the output buffer contains 65 bytes of storage for each block, plus an | |
68 | additional byte for a NUL terminator. EVP_EncodeUpdate() may be called | |
69 | repeatedly to process large amounts of input data. In the event of an error | |
f430ba31 | 70 | EVP_EncodeUpdate() will set B<*outl> to 0 and return 0. On success 1 will be |
cf3404fc | 71 | returned. |
d202a602 MC |
72 | |
73 | EVP_EncodeFinal() must be called at the end of an encoding operation. It will | |
74 | process any partial block of data remaining in the B<ctx> object. The output | |
75 | data will be stored in B<out> and the length of the data written will be stored | |
76 | in B<*outl>. It is the caller's responsibility to ensure that B<out> is | |
77 | sufficiently large to accommodate the output data which will never be more than | |
78 | 65 bytes plus an additional NUL terminator (i.e. 66 bytes in total). | |
79 | ||
c1054bb4 JZ |
80 | EVP_ENCODE_CTX_copy() can be used to copy a context B<sctx> to a context |
81 | B<dctx>. B<dctx> must be initialized before calling this function. | |
82 | ||
d202a602 MC |
83 | EVP_ENCODE_CTX_num() will return the number of as yet unprocessed bytes still to |
84 | be encoded or decoded that are pending in the B<ctx> object. | |
85 | ||
86 | EVP_EncodeBlock() encodes a full block of input data in B<f> and of length | |
87 | B<dlen> and stores it in B<t>. For every 3 bytes of input provided 4 bytes of | |
88 | output data will be produced. If B<dlen> is not divisible by 3 then the block is | |
89 | encoded as a final block of data and the output is padded such that it is always | |
90 | divisible by 4. Additionally a NUL terminator character will be added. For | |
91 | example if 16 bytes of input data is provided then 24 bytes of encoded data is | |
92 | created plus 1 byte for a NUL terminator (i.e. 25 bytes in total). The length of | |
93 | the data generated I<without> the NUL terminator is returned from the function. | |
94 | ||
95 | EVP_DecodeInit() initialises B<ctx> for the start of a new decoding operation. | |
96 | ||
97 | EVP_DecodeUpdate() decodes B<inl> characters of data found in the buffer pointed | |
98 | to by B<in>. The output is stored in the buffer B<out> and the number of bytes | |
99 | output is stored in B<*outl>. It is the caller's responsibility to ensure that | |
100 | the buffer at B<out> is sufficiently large to accommodate the output data. This | |
101 | function will attempt to decode as much data as possible in 4 byte chunks. Any | |
102 | whitespace, newline or carriage return characters are ignored. Any partial chunk | |
103 | of unprocessed data (1, 2 or 3 bytes) that remains at the end will be held in | |
104 | the B<ctx> object and processed by a subsequent call to EVP_DecodeUpdate(). If | |
105 | any illegal base 64 characters are encountered or if the base 64 padding | |
106 | character "=" is encountered in the middle of the data then the function returns | |
107 | -1 to indicate an error. A return value of 0 or 1 indicates successful | |
108 | processing of the data. A return value of 0 additionally indicates that the last | |
109 | input data characters processed included the base 64 padding character "=" and | |
110 | therefore no more non-padding character data is expected to be processed. For | |
111 | every 4 valid base 64 bytes processed (ignoring whitespace, carriage returns and | |
112 | line feeds), 3 bytes of binary output data will be produced (or less at the end | |
113 | of the data where the padding character "=" has been used). | |
114 | ||
115 | EVP_DecodeFinal() must be called at the end of a decoding operation. If there | |
116 | is any unprocessed data still in B<ctx> then the input data must not have been | |
117 | a multiple of 4 and therefore an error has occurred. The function will return -1 | |
118 | in this case. Otherwise the function returns 1 on success. | |
119 | ||
120 | EVP_DecodeBlock() will decode the block of B<n> characters of base 64 data | |
121 | contained in B<f> and store the result in B<t>. Any leading whitespace will be | |
122 | trimmed as will any trailing whitespace, newlines, carriage returns or EOF | |
f430ba31 | 123 | characters. After such trimming the length of the data in B<f> must be divisible |
d202a602 MC |
124 | by 4. For every 4 input bytes exactly 3 output bytes will be produced. The |
125 | output will be padded with 0 bits if necessary to ensure that the output is | |
126 | always 3 bytes for every 4 input bytes. This function will return the length of | |
127 | the data decoded or -1 on error. | |
128 | ||
129 | =head1 RETURN VALUES | |
130 | ||
131 | EVP_ENCODE_CTX_new() returns a pointer to the newly allocated EVP_ENCODE_CTX | |
132 | object or NULL on error. | |
133 | ||
134 | EVP_ENCODE_CTX_num() returns the number of bytes pending encoding or decoding in | |
135 | B<ctx>. | |
136 | ||
cf3404fc MC |
137 | EVP_EncodeUpdate() returns 0 on error or 1 on success. |
138 | ||
d202a602 MC |
139 | EVP_EncodeBlock() returns the number of bytes encoded excluding the NUL |
140 | terminator. | |
141 | ||
142 | EVP_DecodeUpdate() returns -1 on error and 0 or 1 on success. If 0 is returned | |
143 | then no more non-padding base 64 characters are expected. | |
144 | ||
145 | EVP_DecodeFinal() returns -1 on error or 1 on success. | |
146 | ||
147 | EVP_DecodeBlock() returns the length of the data decoded or -1 on error. | |
148 | ||
149 | =head1 SEE ALSO | |
150 | ||
151 | L<evp(3)> | |
152 | ||
e2f92610 RS |
153 | =head1 COPYRIGHT |
154 | ||
155 | Copyright 2016 The OpenSSL Project Authors. All Rights Reserved. | |
156 | ||
157 | Licensed under the OpenSSL license (the "License"). You may not use | |
158 | this file except in compliance with the License. You can obtain a copy | |
159 | in the file LICENSE in the source distribution or at | |
160 | L<https://www.openssl.org/source/license.html>. | |
161 | ||
162 | =cut |