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/*
* Copyright (c) 2018 Thomas Pornin <pornin@bolet.org>
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
#include "inner.h"
/*
* Get the appropriate Base64 character for a numeric value in the
* 0..63 range. This is constant-time.
*/
static char
b64char(uint32_t x)
{
/*
* Values 0 to 25 map to 0x41..0x5A ('A' to 'Z')
* Values 26 to 51 map to 0x61..0x7A ('a' to 'z')
* Values 52 to 61 map to 0x30..0x39 ('0' to '9')
* Value 62 maps to 0x2B ('+')
* Value 63 maps to 0x2F ('/')
*/
uint32_t a, b, c;
a = x - 26;
b = x - 52;
c = x - 62;
/*
* Looking at bits 8..15 of values a, b and c:
*
* x a b c
* ---------------------
* 0..25 FF FF FF
* 26..51 00 FF FF
* 52..61 00 00 FF
* 62..63 00 00 00
*/
return (char)(((x + 0x41) & ((a & b & c) >> 8))
| ((x + (0x61 - 26)) & ((~a & b & c) >> 8))
| ((x - (52 - 0x30)) & ((~a & ~b & c) >> 8))
| ((0x2B + ((x & 1) << 2)) & (~(a | b | c) >> 8)));
}
/* see bearssl_pem.h */
size_t
br_pem_encode(void *dest, const void *data, size_t len,
const char *banner, unsigned flags)
{
size_t dlen, banner_len, lines;
char *d;
unsigned char *buf;
size_t u;
int off, lim;
banner_len = strlen(banner);
/* FIXME: try to avoid divisions here, as they may pull
an extra libc function. */
if ((flags & BR_PEM_LINE64) != 0) {
lines = (len + 47) / 48;
} else {
lines = (len + 56) / 57;
}
dlen = (banner_len << 1) + 30 + (((len + 2) / 3) << 2)
+ lines + 2;
if ((flags & BR_PEM_CRLF) != 0) {
dlen += lines + 2;
}
if (dest == NULL) {
return dlen;
}
d = dest;
/*
* We always move the source data to the end of output buffer;
* the encoding process never "catches up" except at the very
* end. This also handles all conditions of partial or total
* overlap.
*/
buf = (unsigned char *)d + dlen - len;
memmove(buf, data, len);
memcpy(d, "-----BEGIN ", 11);
d += 11;
memcpy(d, banner, banner_len);
d += banner_len;
memcpy(d, "-----", 5);
d += 5;
if ((flags & BR_PEM_CRLF) != 0) {
*d ++ = 0x0D;
}
*d ++ = 0x0A;
off = 0;
lim = (flags & BR_PEM_LINE64) != 0 ? 16 : 19;
for (u = 0; (u + 2) < len; u += 3) {
uint32_t w;
w = ((uint32_t)buf[u] << 16)
| ((uint32_t)buf[u + 1] << 8)
| (uint32_t)buf[u + 2];
*d ++ = b64char(w >> 18);
*d ++ = b64char((w >> 12) & 0x3F);
*d ++ = b64char((w >> 6) & 0x3F);
*d ++ = b64char(w & 0x3F);
if (++ off == lim) {
off = 0;
if ((flags & BR_PEM_CRLF) != 0) {
*d ++ = 0x0D;
}
*d ++ = 0x0A;
}
}
if (u < len) {
uint32_t w;
w = (uint32_t)buf[u] << 16;
if (u + 1 < len) {
w |= (uint32_t)buf[u + 1] << 8;
}
*d ++ = b64char(w >> 18);
*d ++ = b64char((w >> 12) & 0x3F);
if (u + 1 < len) {
*d ++ = b64char((w >> 6) & 0x3F);
} else {
*d ++ = 0x3D;
}
*d ++ = 0x3D;
off ++;
}
if (off != 0) {
if ((flags & BR_PEM_CRLF) != 0) {
*d ++ = 0x0D;
}
*d ++ = 0x0A;
}
memcpy(d, "-----END ", 9);
d += 9;
memcpy(d, banner, banner_len);
d += banner_len;
memcpy(d, "-----", 5);
d += 5;
if ((flags & BR_PEM_CRLF) != 0) {
*d ++ = 0x0D;
}
*d ++ = 0x0A;
/* Final zero, not counted in returned length. */
*d ++ = 0x00;
return dlen;
}
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