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crypto: ECDH convertKey to convert public keys between different formats #19080

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41a17db
crypto: ECDH function to convert public keys
wuweiweiwu Mar 2, 2018
9ded80c
crypto: refactoring shared code
wuweiweiwu Mar 2, 2018
e876f36
test: adding tests for ECDH#convertKey
wuweiweiwu Mar 2, 2018
810cb37
doc: adding docs for ECDH#convertKey
wuweiweiwu Mar 3, 2018
17f1703
crypto: clean up pointers on failure
wuweiweiwu Mar 4, 2018
d5f07d9
crypto: minor fixes
wuweiweiwu Mar 5, 2018
c201c26
crypto: input typechecking
wuweiweiwu Mar 5, 2018
541a651
crypto: using the updated errors
wuweiweiwu Mar 10, 2018
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crypto: ECDH function to convert public keys 
ECDH.convertKey is used to convert public keys
between different formats.

Fixes: #18977
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@wuweiweiwu
wuweiweiwu committed Mar 10, 2018
commit 41a17db2df9e75ee336225675ff09768ddad970a
27 changes: 26 additions & 1 deletion lib/internal/crypto/diffiehellman.js
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Original file line number Diff line number Diff line change
Expand Up @@ -14,7 +14,8 @@ const {
const {
DiffieHellman: _DiffieHellman,
DiffieHellmanGroup: _DiffieHellmanGroup,
ECDH: _ECDH
ECDH: _ECDH,
ECDHConvertKey: _ECDHConvertKey
} = process.binding('crypto');
const {
POINT_CONVERSION_COMPRESSED,
Expand Down Expand Up @@ -218,6 +219,30 @@ ECDH.prototype.getPublicKey = function getPublicKey(encoding, format) {
return key;
};

ECDH.convertKey = function convertKey(key, curve, inEnc, outEnc, format) {
const encoding = getDefaultEncoding();
inEnc = inEnc || encoding;
outEnc = outEnc || encoding;
var f;
if (format) {
if (format === 'compressed')
f = POINT_CONVERSION_COMPRESSED;
else if (format === 'hybrid')
f = POINT_CONVERSION_HYBRID;
// Default
else if (format === 'uncompressed')
f = POINT_CONVERSION_UNCOMPRESSED;
else
throw new errors.TypeError('ERR_CRYPTO_ECDH_INVALID_FORMAT', format);
} else {
f = POINT_CONVERSION_UNCOMPRESSED;
}
var convertedKey = _ECDHConvertKey(toBuf(key, inEnc), curve, f);
if (outEnc && outEnc !== 'buffer')
convertedKey = convertedKey.toString(outEnc);
return convertedKey;
};
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@bnoordhuis bnoordhuis Mar 2, 2018

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Don't duplicate this logic, factor it out so it can be shared with ECDH#getPublicKey(). Likewise the C++ code.

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@wuweiweiwu wuweiweiwu Mar 2, 2018

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Done!


module.exports = {
DiffieHellman,
DiffieHellmanGroup,
Expand Down
68 changes: 68 additions & 0 deletions src/node_crypto.cc
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Expand Up @@ -5550,6 +5550,72 @@ void ExportChallenge(const FunctionCallbackInfo<Value>& args) {
args.GetReturnValue().Set(outString);
}


// convert public key to compressed, uncompressed, hybrid format
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@bnoordhuis bnoordhuis Mar 3, 2018

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Can you capitalize and punctuate the comments?

void ConvertKey(const FunctionCallbackInfo<Value>& args) {
Environment* env = Environment::GetCurrent(args);

CHECK_EQ(args.Length(), 3);

THROW_AND_RETURN_IF_NOT_BUFFER(args[0], "Public key");
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@jasnell jasnell Mar 5, 2018

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Since this is adding a new API, please handle the input type checking in javascript and use the internal/errors mechanism.

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@wuweiweiwu wuweiweiwu Mar 5, 2018 •
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Done! :)


size_t len = Buffer::Length(args[0]);
if (len == 0)
return args.GetReturnValue().SetEmptyString();

THROW_AND_RETURN_IF_NOT_STRING(args[1], "ECDH curve name");
node::Utf8Value curve(env->isolate(), args[1]);

int nid = OBJ_sn2nid(*curve);
if (nid == NID_undef)
return env->ThrowTypeError("Second argument should be a valid curve name");

EC_GROUP* group = EC_GROUP_new_by_curve_name(nid);
if (group == nullptr)
return env->ThrowError("Failed to get EC_GROUP");

EC_POINT* pub = EC_POINT_new(group);
if (pub == nullptr)
return env->ThrowError("Failed to allocate EC_POINT for a public key");

int r = EC_POINT_oct2point(
group,
pub,
reinterpret_cast<unsigned char*>(Buffer::Data(args[0])),
len,
nullptr);
if (!r)
return env->ThrowError("Failed to convert key to point");

if (pub == nullptr)
return env->ThrowError("Failed to convert Buffer to EC_POINT");
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@bnoordhuis bnoordhuis Mar 3, 2018 •
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Leaks group. group and pub are leaked on lines 5580 and 5587.

Suggestion: use a std::unique_ptr with a custom deleter or use the std::shared_ptr trick from 8ccd320.


// convert to the specified format
int size;
point_conversion_form_t form =
static_cast<point_conversion_form_t>(args[2]->Uint32Value());

size = EC_POINT_point2oct(group, pub, form, nullptr, 0, nullptr);
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@bnoordhuis bnoordhuis Mar 3, 2018

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Minor thing but can you write this as int size = ...?

if (size == 0)
return env->ThrowError("Failed to get public key length");

unsigned char* out = node::Malloc<unsigned char>(size);

r = EC_POINT_point2oct(group, pub, form, out, size, nullptr);
if (r != size) {
free(out);
return env->ThrowError("Failed to get public key");
}

Local<Object> buf =
Buffer::New(env, reinterpret_cast<char*>(out), size).ToLocalChecked();
args.GetReturnValue().Set(buf);

EC_GROUP_free(group);
EC_POINT_free(pub);
}


void TimingSafeEqual(const FunctionCallbackInfo<Value>& args) {
CHECK(Buffer::HasInstance(args[0]));
CHECK(Buffer::HasInstance(args[1]));
Expand Down Expand Up @@ -5692,6 +5758,8 @@ void InitCrypto(Local<Object> target,
env->SetMethod(target, "certVerifySpkac", VerifySpkac);
env->SetMethod(target, "certExportPublicKey", ExportPublicKey);
env->SetMethod(target, "certExportChallenge", ExportChallenge);

env->SetMethod(target, "ECDHConvertKey", ConvertKey);
#ifndef OPENSSL_NO_ENGINE
env->SetMethod(target, "setEngine", SetEngine);
#endif // !OPENSSL_NO_ENGINE
Expand Down