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crypto: warn on invalid authentication tag length #17566

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crypto: warn on invalid authentication tag length #17566

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c5d0372
test: use valid authentication tag length
tniessen Dec 9, 2017
fc6c652
crypto: warn on invalid authentication tag length
tniessen Dec 9, 2017
54d49c1
[squash] remove GCM check
tniessen Dec 10, 2017
bbf356e
[squash] fix FIPS failure
tniessen Dec 10, 2017
0b5c90f
[squash] fix FIPS (again)
tniessen Dec 10, 2017
e694393
[squash] add dot
tniessen Dec 11, 2017
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12 changes: 10 additions & 2 deletions src/node_crypto.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -3767,9 +3767,17 @@ void CipherBase::SetAuthTag(const FunctionCallbackInfo<Value>& args) {
return args.GetReturnValue().Set(false);
}

// FIXME(bnoordhuis) Throw when buffer length is not a valid tag size.
// Restrict GCM tag lengths according to NIST 800-38d, page 9
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Dot at the end.

unsigned int tag_len = Buffer::Length(args[0]);
if (tag_len > 16 || (tag_len < 12 && tag_len != 8 && tag_len != 4)) {
ProcessEmitWarning(cipher->env(),
"Permitting authentication tag lengths of %u bytes is deprecated. "
"Valid GCM tag lengths are 4, 8, 12, 13, 14, 15, 16.",
tag_len);
}

// Note: we don't use std::max() here to work around a header conflict.
cipher->auth_tag_len_ = Buffer::Length(args[0]);
cipher->auth_tag_len_ = tag_len;
if (cipher->auth_tag_len_ > sizeof(cipher->auth_tag_))
cipher->auth_tag_len_ = sizeof(cipher->auth_tag_);

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19 changes: 19 additions & 0 deletions test/parallel/test-crypto-authenticated.js
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Expand Up @@ -335,6 +335,14 @@ const errMessages = {

const ciphers = crypto.getCiphers();

common.expectWarning('Warning', (common.hasFipsCrypto ? [] : [
'Use Cipheriv for counter mode of aes-192-gcm'
]).concat(
[0, 1, 2, 6, 9, 10, 11, 17]
.map((i) => `Permitting authentication tag lengths of ${i} bytes is ` +
'deprecated. Valid GCM tag lengths are 4, 8, 12, 13, 14, 15, 16.')
));

for (const i in TEST_CASES) {
const test = TEST_CASES[i];

Expand Down Expand Up @@ -476,3 +484,14 @@ for (const i in TEST_CASES) {
assert.throws(() => encrypt.setAAD(Buffer.from('123', 'ascii')),
errMessages.state);
}

// GCM only supports specific authentication tag lengths, invalid lengths should
// produce warnings.
{
for (const length of [0, 1, 2, 4, 6, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17]) {
const decrypt = crypto.createDecipheriv('aes-256-gcm',
'FxLKsqdmv0E9xrQhp0b1ZgI0K7JFZJM8',
'qkuZpJWCewa6Szih');
decrypt.setAuthTag(Buffer.from('1'.repeat(length)));
}
}
2 changes: 1 addition & 1 deletion test/parallel/test-crypto-cipher-decipher.js
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Expand Up @@ -216,7 +216,7 @@ testCipher2(Buffer.from('0123456789abcdef'));
// setAutoPadding/setAuthTag/setAAD should return `this`
{
const key = '0123456789';
const tagbuf = Buffer.from('tagbuf');
const tagbuf = Buffer.from('auth_tag');
const aadbuf = Buffer.from('aadbuf');
const decipher = crypto.createDecipher('aes-256-gcm', key);
assert.strictEqual(decipher.setAutoPadding(), decipher);
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