Fix/refactor: Refactor validate method to not use non-validated data #89
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peterthomassen
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Feb 9, 2021
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Previously, Connaisseur accepted all trust data files at first and then validated them. This was not an immediate security issue, since the root key could not be overwritten and since the KeyStore is write-once, so keys will only be used after they have been validated. However, Connaisseur would have pulled all delegations in a malicious targets.json without prior validation, which would have allowed an attacker to specify many non-existant delegations, potentially causing a denial of service. This commit fixes the issue by first validating and then processing the trust data files. In addition, the way Connaisseur previously validated trust data files would have allowed an attacker that compromised the long-term snapshot key to mount freeze attacks (i.e. ignoring the validation via timestamp key) by mounting a targeted collision attack instead of a 2nd-preimage attack against the DCT hash function.
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phbelitz
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Mar 12, 2021
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Previously, Connaisseur accepted all trust data files at first and then validated them. This was not an immediate security issue, since the root key could not be overwritten and since the KeyStore is write-once, so keys will only be used after they have been validated. However, Connaisseur would have pulled all delegations in a malicious targets.json without prior validation, which would have allowed an attacker to specify many non-existant delegations, potentially causing a denial of service. This PR fixes the issue by first validating and then processing the trust data files. In addition, the way Connaisseur previously validated trust data files would have allowed an attacker that compromised the long-term snapshot key to mount freeze attacks (i.e. ignoring the validation via timestamp key) by mounting a targeted collision attack instead of a 2nd-preimage attack against the DCT hash function.