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'use strict';
var Buffer = require('safe-buffer').Buffer;
var getParamBytesForAlg = require('./param-bytes-for-alg');
var MAX_OCTET = 0x80,
CLASS_UNIVERSAL = 0,
PRIMITIVE_BIT = 0x20,
TAG_SEQ = 0x10,
TAG_INT = 0x02,
ENCODED_TAG_SEQ = (TAG_SEQ | PRIMITIVE_BIT) | (CLASS_UNIVERSAL << 6),
ENCODED_TAG_INT = TAG_INT | (CLASS_UNIVERSAL << 6);
function base64Url(base64) {
return base64
.replace(/=/g, '')
.replace(/\+/g, '-')
.replace(/\//g, '_');
}
function signatureAsBuffer(signature) {
if (Buffer.isBuffer(signature)) {
return signature;
} else if ('string' === typeof signature) {
return Buffer.from(signature, 'base64');
}
throw new TypeError('ECDSA signature must be a Base64 string or a Buffer');
}
function derToJose(signature, alg) {
signature = signatureAsBuffer(signature);
var paramBytes = getParamBytesForAlg(alg);
// the DER encoded param should at most be the param size, plus a padding
// zero, since due to being a signed integer
var maxEncodedParamLength = paramBytes + 1;
var inputLength = signature.length;
var offset = 0;
if (signature[offset++] !== ENCODED_TAG_SEQ) {
throw new Error('Could not find expected "seq"');
}
var seqLength = signature[offset++];
if (seqLength === (MAX_OCTET | 1)) {
seqLength = signature[offset++];
}
if (inputLength - offset < seqLength) {
throw new Error('"seq" specified length of "' + seqLength + '", only "' + (inputLength - offset) + '" remaining');
}
if (signature[offset++] !== ENCODED_TAG_INT) {
throw new Error('Could not find expected "int" for "r"');
}
var rLength = signature[offset++];
if (inputLength - offset - 2 < rLength) {
throw new Error('"r" specified length of "' + rLength + '", only "' + (inputLength - offset - 2) + '" available');
}
if (maxEncodedParamLength < rLength) {
throw new Error('"r" specified length of "' + rLength + '", max of "' + maxEncodedParamLength + '" is acceptable');
}
var rOffset = offset;
offset += rLength;
if (signature[offset++] !== ENCODED_TAG_INT) {
throw new Error('Could not find expected "int" for "s"');
}
var sLength = signature[offset++];
if (inputLength - offset !== sLength) {
throw new Error('"s" specified length of "' + sLength + '", expected "' + (inputLength - offset) + '"');
}
if (maxEncodedParamLength < sLength) {
throw new Error('"s" specified length of "' + sLength + '", max of "' + maxEncodedParamLength + '" is acceptable');
}
var sOffset = offset;
offset += sLength;
if (offset !== inputLength) {
throw new Error('Expected to consume entire buffer, but "' + (inputLength - offset) + '" bytes remain');
}
var rPadding = paramBytes - rLength,
sPadding = paramBytes - sLength;
var dst = Buffer.allocUnsafe(rPadding + rLength + sPadding + sLength);
for (offset = 0; offset < rPadding; ++offset) {
dst[offset] = 0;
}
signature.copy(dst, offset, rOffset + Math.max(-rPadding, 0), rOffset + rLength);
offset = paramBytes;
for (var o = offset; offset < o + sPadding; ++offset) {
dst[offset] = 0;
}
signature.copy(dst, offset, sOffset + Math.max(-sPadding, 0), sOffset + sLength);
dst = dst.toString('base64');
dst = base64Url(dst);
return dst;
}
function countPadding(buf, start, stop) {
var padding = 0;
while (start + padding < stop && buf[start + padding] === 0) {
++padding;
}
var needsSign = buf[start + padding] >= MAX_OCTET;
if (needsSign) {
--padding;
}
return padding;
}
function joseToDer(signature, alg) {
signature = signatureAsBuffer(signature);
var paramBytes = getParamBytesForAlg(alg);
var signatureBytes = signature.length;
if (signatureBytes !== paramBytes * 2) {
throw new TypeError('"' + alg + '" signatures must be "' + paramBytes * 2 + '" bytes, saw "' + signatureBytes + '"');
}
var rPadding = countPadding(signature, 0, paramBytes);
var sPadding = countPadding(signature, paramBytes, signature.length);
var rLength = paramBytes - rPadding;
var sLength = paramBytes - sPadding;
var rsBytes = 1 + 1 + rLength + 1 + 1 + sLength;
var shortLength = rsBytes < MAX_OCTET;
var dst = Buffer.allocUnsafe((shortLength ? 2 : 3) + rsBytes);
var offset = 0;
dst[offset++] = ENCODED_TAG_SEQ;
if (shortLength) {
// Bit 8 has value "0"
// bits 7-1 give the length.
dst[offset++] = rsBytes;
} else {
// Bit 8 of first octet has value "1"
// bits 7-1 give the number of additional length octets.
dst[offset++] = MAX_OCTET | 1;
// length, base 256
dst[offset++] = rsBytes & 0xff;
}
dst[offset++] = ENCODED_TAG_INT;
dst[offset++] = rLength;
if (rPadding < 0) {
dst[offset++] = 0;
offset += signature.copy(dst, offset, 0, paramBytes);
} else {
offset += signature.copy(dst, offset, rPadding, paramBytes);
}
dst[offset++] = ENCODED_TAG_INT;
dst[offset++] = sLength;
if (sPadding < 0) {
dst[offset++] = 0;
signature.copy(dst, offset, paramBytes);
} else {
signature.copy(dst, offset, paramBytes + sPadding);
}
return dst;
}
module.exports = {
derToJose: derToJose,
joseToDer: joseToDer
};
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