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