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/* base64 routines.
*
* (C) 2003-2020 Anope Team
* Contact us at team@anope.org
*
* Please read COPYING and README for further details.
*
* Based on the original code of Epona by Lara.
* Based on the original code of Services by Andy Church.
*/
#include "services.h"
#include "anope.h"
static const Anope::string Base64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
static const char Pad64 = '=';
/* (From RFC1521 and draft-ietf-dnssec-secext-03.txt)
The following encoding technique is taken from RFC 1521 by Borenstein
and Freed. It is reproduced here in a slightly edited form for
convenience.
A 65-character subset of US-ASCII is used, enabling 6 bits to be
represented per printable character. (The extra 65th character, "=",
is used to signify a special processing function.)
The encoding process represents 24-bit groups of input bits as output
strings of 4 encoded characters. Proceeding from left to right, a
24-bit input group is formed by concatenating 3 8-bit input groups.
These 24 bits are then treated as 4 concatenated 6-bit groups, each
of which is translated into a single digit in the base64 alphabet.
Each 6-bit group is used as an index into an array of 64 printable
characters. The character referenced by the index is placed in the
output string.
Table 1: The Base64 Alphabet
Value Encoding Value Encoding Value Encoding Value Encoding
0 A 17 R 34 i 51 z
1 B 18 S 35 j 52 0
2 C 19 T 36 k 53 1
3 D 20 U 37 l 54 2
4 E 21 V 38 m 55 3
5 F 22 W 39 n 56 4
6 G 23 X 40 o 57 5
7 H 24 Y 41 p 58 6
8 I 25 Z 42 q 59 7
9 J 26 a 43 r 60 8
10 K 27 b 44 s 61 9
11 L 28 c 45 t 62 +
12 M 29 d 46 u 63 /
13 N 30 e 47 v
14 O 31 f 48 w (pad) =
15 P 32 g 49 x
16 Q 33 h 50 y
Special processing is performed if fewer than 24 bits are available
at the end of the data being encoded. A full encoding quantum is
always completed at the end of a quantity. When fewer than 24 input
bits are available in an input group, zero bits are added (on the
right) to form an integral number of 6-bit groups. Padding at the
end of the data is performed using the '=' character.
Since all base64 input is an integral number of octets, only the
-------------------------------------------------
following cases can arise:
(1) the final quantum of encoding input is an integral
multiple of 24 bits; here, the final unit of encoded
output will be an integral multiple of 4 characters
with no "=" padding,
(2) the final quantum of encoding input is exactly 8 bits;
here, the final unit of encoded output will be two
characters followed by two "=" padding characters, or
(3) the final quantum of encoding input is exactly 16 bits;
here, the final unit of encoded output will be three
characters followed by one "=" padding character.
*/
void Anope::B64Encode(const Anope::string &src, Anope::string &target)
{
size_t src_pos = 0, src_len = src.length();
unsigned char input[3] = { '\0', '\0', '\0' };
target.clear();
while (src_len - src_pos > 2)
{
input[0] = src[src_pos++];
input[1] = src[src_pos++];
input[2] = src[src_pos++];
target += Base64[input[0] >> 2];
target += Base64[((input[0] & 0x03) << 4) + (input[1] >> 4)];
target += Base64[((input[1] & 0x0f) << 2) + (input[2] >> 6)];
target += Base64[input[2] & 0x3f];
}
/* Now we worry about padding */
if (src_pos != src_len)
{
input[0] = input[1] = input[2] = 0;
for (size_t i = 0; i < src_len - src_pos; ++i)
input[i] = src[src_pos + i];
target += Base64[input[0] >> 2];
target += Base64[((input[0] & 0x03) << 4) + (input[1] >> 4)];
if (src_pos == src_len - 1)
target += Pad64;
else
target += Base64[((input[1] & 0x0f) << 2) + (input[2] >> 6)];
target += Pad64;
}
}
/* skips all whitespace anywhere.
converts characters, four at a time, starting at (or after)
src from base - 64 numbers into three 8 bit bytes in the target area.
*/
void Anope::B64Decode(const Anope::string &src, Anope::string &target)
{
target.clear();
unsigned state = 0;
Anope::string::const_iterator ch = src.begin(), end = src.end();
for (; ch != end; ++ch)
{
if (isspace(*ch)) /* Skip whitespace anywhere */
continue;
if (*ch == Pad64)
break;
size_t pos = Base64.find(*ch);
if (pos == Anope::string::npos) /* A non-base64 character */
return;
switch (state)
{
case 0:
target += pos << 2;
state = 1;
break;
case 1:
target[target.length() - 1] |= pos >> 4;
target += (pos & 0x0f) << 4;
state = 2;
break;
case 2:
target[target.length() - 1] |= pos >> 2;
target += (pos & 0x03) << 6;
state = 3;
break;
case 3:
target[target.length() - 1] |= pos;
state = 0;
}
}
if (!target.empty() && !target[target.length() - 1])
target.erase(target.length() - 1);
}
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