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update rekor intoto/0.0.2 entry hash calculation #151

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merged 2 commits into from
Nov 4, 2022
Merged

update rekor intoto/0.0.2 entry hash calculation #151

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c47e6b3
update rekor intoto/0.0.2 entry hash calculation
bdehamer Nov 3, 2022
32ffd2d
add more tests for dsse hash calculation
bdehamer Nov 3, 2022
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59 changes: 55 additions & 4 deletions src/tlog/format.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -92,6 +92,12 @@ describe('format', () => {
);
expect(entry.spec.content.hash).toBeTruthy();
expect(entry.spec.content.hash?.algorithm).toBe('sha256');

// This hard-coded hash value helps us detect if we've unintentionally
// changed the hashing algorithm.
expect(entry.spec.content.hash?.value).toBe(
'91a5eb7452452720d704da5442acb9703252b3ab7be51ec155a244f5c9aa5ec8'
);
});
});

Expand All @@ -105,12 +111,57 @@ describe('format', () => {
it('returns a valid intoto entry', () => {
const entry = toProposedIntotoEntry(envelope, sigMaterial);

if (typeof entry.spec.content.envelope !== 'string') {
const e = entry.spec.content.envelope;
expect(e?.signatures[0].keyid).toBeUndefined();
} else {
if (typeof entry.spec.content.envelope === 'string') {
fail('intoto type is v0.0.1 but expecting v0.0.2');
}

// Ensure the keyid is not included in the envelope.
const e = entry.spec.content.envelope;
expect(e?.signatures).toHaveLength(1);
expect(e?.signatures[0].keyid).toBeUndefined();
expect(e?.signatures[0].sig).toEqual(
enc.base64Encode(envelope.signatures[0].sig.toString('base64'))
);

// This hard-coded hash value helps us detect if we've unintentionally
// changed the hashing algorithm.
expect(entry.spec.content.hash?.value).toBe(
'295fd391f3b3f349cdaa686befaa765d90c0b411a0811e45f8bc481338a51622'
);
});
});

describe('when there are multiple signatures in the envelope', () => {
const envelope: Envelope = {
payloadType: 'application/vnd.in-toto+json',
payload: Buffer.from('payload'),
signatures: [
{ keyid: '123', sig: signature },
{ keyid: '', sig: signature },
],
};

it('returns a valid intoto entry', () => {
const entry = toProposedIntotoEntry(envelope, sigMaterial);

if (typeof entry.spec.content.envelope === 'string') {
fail('intoto type is v0.0.1 but expecting v0.0.2');
}

// Check to ensure only the first signature is included in the envelope
const e = entry.spec.content.envelope;
expect(e?.signatures).toHaveLength(1);
expect(e?.signatures[0].keyid).toEqual(envelope.signatures[0].keyid);
expect(e?.signatures[0].sig).toEqual(
enc.base64Encode(envelope.signatures[0].sig.toString('base64'))
);
expect(e?.signatures[0].publicKey).toEqual(enc.base64Encode(cert));

// This hard-coded hash value helps us detect if we've unintentionally
// changed the hashing algorithm.
expect(entry.spec.content.hash?.value).toBe(
'91a5eb7452452720d704da5442acb9703252b3ab7be51ec155a244f5c9aa5ec8'
);
});
});
});
Expand Down
36 changes: 32 additions & 4 deletions src/tlog/format.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -75,14 +75,22 @@ function toProposedIntotoV002Entry(
envelope: Envelope,
signature: SignatureMaterial
): IntotoKind {
// Calculate the value for the payloadHash field in the Rekor entry
const payloadHash = crypto.hash(envelope.payload).toString('hex');

// Calculate the value for the hash field in the Rekor entry
const envelopeHash = calculateDSSEHash(envelope);

// Collect values for re-creating the DSSE envelope.
// Double-encode payload and signature cause that's what Rekor expects
const payload = enc.base64Encode(envelope.payload.toString('base64'));
const sig = enc.base64Encode(envelope.signatures[0].sig.toString('base64'));
const keyid = envelope.signatures[0].keyid;
const publicKey = enc.base64Encode(toPublicKey(signature));
const payloadHash = crypto.hash(envelope.payload).toString('hex');

// Create the envelop portion first so that we can calculate its hash
// Create the envelope portion of the entry. Note the inclusion of the
// publicKey in the signature struct is not a standard part of a DSSE
// envelope, but is required by Rekor.
const dsse: IntotoKind['spec']['content']['envelope'] = {
payloadType: envelope.payloadType,
payload: payload,
Expand All @@ -96,8 +104,6 @@ function toProposedIntotoV002Entry(
dsse.signatures[0].keyid = keyid;
}

const envelopeHash = crypto.hash(json.canonicalize(dsse)).toString('hex');

return {
apiVersion: '0.0.2',
kind: INTOTO_KIND,
Expand All @@ -111,6 +117,28 @@ function toProposedIntotoV002Entry(
};
}

// Calculates the hash of a DSSE envelope for inclusion in a Rekor entry.
// There is no standard way to do this, so the scheme we're using as as
// follows:
// * payload is base64 encoded
// * signature is base64 encoded (only the first signature is used)
// * keyid is included ONLY if it is NOT an empty string
// * The resulting JSON is canonicalized and hashed to a hex string
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Yikes!

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Is it worth writing some kind of tests around this behaviour to make sure we don't deviate from it in future?

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Do we have some tests in src/tlog/verify.test.ts that create different kinds of envelopes with and without a keyid? Maybe with multiple sigs?

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@feelepxyz I added some more tests around the DSSE hash calculation to ensure that we don't unintentionally alter it.

function calculateDSSEHash(envelope: Envelope): string {
const dsse: IntotoKind['spec']['content']['envelope'] = {
payloadType: envelope.payloadType,
payload: envelope.payload.toString('base64'),
signatures: [{ sig: envelope.signatures[0].sig.toString('base64') }],
};

// If the keyid is an empty string, Rekor seems to remove it altogether.
if (envelope.signatures[0].keyid.length > 0) {
dsse.signatures[0].keyid = envelope.signatures[0].keyid;
}

return crypto.hash(json.canonicalize(dsse)).toString('hex');
}

function toPublicKey(signature: SignatureMaterial): string {
return signature.certificates
? signature.certificates[0]
Expand Down
10 changes: 5 additions & 5 deletions src/tlog/verify.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -79,7 +79,7 @@ kBbmLSGtks4L3qX6yYY0zufBnhC8Ur/iy55GhWP/9A/bY2LhC30M9+RYtw==

describe('when a DSSE Bundle is provided', () => {
const set = Buffer.from(
'MEYCIQC/9HHAv5Fg4uCxtmkxRqXznZcQchktwV5f4f6/XdCjsQIhAIJTMDf+PbrDL1p6rr2lS/yq/iYnscFkclNrr0a03qdv',
'MEYCIQDCDqNKrxg0g2J/psG5ypPTcxiEoSXSj93G1GhaitBnswIhAM6WDzaJTCkQ2h39jv7vmthAlKZQNRH6Stqxy0Fi4k+C',
'base64'
);

Expand Down Expand Up @@ -169,7 +169,7 @@ function createMessageSignatureBundle(logID: Buffer, set?: Buffer): Bundle {

function createDSSEBundle(logID: Buffer, set?: Buffer): Bundle {
const cert1 = Buffer.from(
'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',
'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',
'base64'
);
const cert2 = Buffer.from(
Expand All @@ -192,7 +192,7 @@ function createDSSEBundle(logID: Buffer, set?: Buffer): Bundle {
{
keyid: '',
sig: Buffer.from(
'MEUCIQCdJHpwUUS919xv5M4cgYt8SGb5gMdPSdamfzFEReF+UgIgAKDrzm9uszoRHeo2Prz4nKRAhcl6k8MXuFzQ3dzXQmU=',
'MEUCIQCVCPbzc4aPZMKpXnwuqbUp6WNDqSHFVfvPmSVSYz+sIgIgEUltpzCXjguuMHlx8qXHJCuH6ptaTmW57llQJRGqQfc=',
'base64'
),
},
Expand All @@ -217,12 +217,12 @@ function createDSSEBundle(logID: Buffer, set?: Buffer): Bundle {
},
tlogEntries: [
{
logIndex: '6083446',
logIndex: '6387817',
logId: {
keyId: logID,
},
kindVersion: { kind: 'intoto', version: '0.0.2' },
integratedTime: '1667019113',
integratedTime: '1667431475',
inclusionPromise: set ? { signedEntryTimestamp: set } : undefined,
inclusionProof: undefined,
},
Expand Down