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fix: KMS client plaintext byteOffset (generate too) #47

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Merged
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Apr 16, 2019
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fix: KMS client plaintext byteOffset (generate too) #47

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12 changes: 12 additions & 0 deletions modules/kms-keyring/src/helpers.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -40,6 +40,18 @@ export async function generateDataKey<Client extends KMS> (

/* Postcondition: KMS must return serializable generate data key. */
if (!isRequiredGenerateDataKeyOutput<typeof dataKey>(dataKey)) throw new Error('Malformed KMS response.')

/* The KMS Client *may* return a Buffer that is not isolated.
* i.e. the byteOffset !== 0.
* This means that the unencrypted data key is possibly accessible to someone else.
* If this is the node shared Buffer, then other code within this process _could_ find this secret.
* Copy Plaintext to an isolated ArrayBuffer and zero the Plaintext.
* This means that this function will *always* zero out the value returned to it from the KMS client.
* While this is safe to do here, copying this code somewhere else may produce unexpected results.
*/
const {Plaintext} = dataKey
dataKey.Plaintext = new Uint8Array(Plaintext)
Plaintext.fill(0)
return dataKey
}

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