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/*
* Copyright (c) 2016 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"
/*
* Compute ASN.1 encoded length for the provided integer. The ASN.1
* encoding is signed, so its leading bit must have value 0; it must
* also be of minimal length (so leading bytes of value 0 must be
* removed, except if that would contradict the rule about the sign
* bit).
*/
static size_t
asn1_int_length(const unsigned char *x, size_t xlen)
{
while (xlen > 0 && *x == 0) {
x ++;
xlen --;
}
if (xlen == 0 || *x >= 0x80) {
xlen ++;
}
return xlen;
}
/* see bearssl_ec.h */
size_t
br_ecdsa_raw_to_asn1(void *sig, size_t sig_len)
{
/*
* Internal buffer is large enough to accommodate a signature
* such that r and s fit on 125 bytes each (signed encoding),
* meaning a curve order of up to 999 bits. This is the limit
* that ensures "simple" length encodings.
*/
unsigned char *buf;
size_t hlen, rlen, slen, zlen, off;
unsigned char tmp[257];
buf = sig;
if ((sig_len & 1) != 0) {
return 0;
}
/*
* Compute lengths for the two integers.
*/
hlen = sig_len >> 1;
rlen = asn1_int_length(buf, hlen);
slen = asn1_int_length(buf + hlen, hlen);
if (rlen > 125 || slen > 125) {
return 0;
}
/*
* SEQUENCE header.
*/
tmp[0] = 0x30;
zlen = rlen + slen + 4;
if (zlen >= 0x80) {
tmp[1] = 0x81;
tmp[2] = zlen;
off = 3;
} else {
tmp[1] = zlen;
off = 2;
}
/*
* First INTEGER (r).
*/
tmp[off ++] = 0x02;
tmp[off ++] = rlen;
if (rlen > hlen) {
tmp[off] = 0x00;
memcpy(tmp + off + 1, buf, hlen);
} else {
memcpy(tmp + off, buf + hlen - rlen, rlen);
}
off += rlen;
/*
* Second INTEGER (s).
*/
tmp[off ++] = 0x02;
tmp[off ++] = slen;
if (slen > hlen) {
tmp[off] = 0x00;
memcpy(tmp + off + 1, buf + hlen, hlen);
} else {
memcpy(tmp + off, buf + sig_len - slen, slen);
}
off += slen;
/*
* Return ASN.1 signature.
*/
memcpy(sig, tmp, off);
return off;
}
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