Fix decodeCertify always returning a truncated signature in case of ECDSA signature.
#192
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… `ECDSA` signature. This is mainly due to the fact that the old code called `tpmutil.UnpackBuf` on only one element that is `signature`. This worked for RSA signatures as their corresponding structure `TPMS_SIGNATURE_RSASSA` contains only 1 field `TPM2B_PUBLIC_KEY_RSA`, in addition to `TPMI_ALG_HASH` field. However, it failed for ECDSA signatures because their corresponding structure is `TPMS_SIGNATURE_ECDSA`, which contains 2 fields R and S - instead of just 1 - which are both `TPM2B_ECC_PARAMETER`, in addition to `TPMI_ALG_HASH` field. Therefore, this can be fixed by calling `tpmutil.UnpackBuf` on 2 elements, that is R followed by S, which results in retrieving the whole signature. Signed-off-by: El Mostafa IDRASSI <mostafa.idrassi@tutanota.com>
ElMostafaIdrassi
requested review from
josephlr and
twitchy-jsonp
as code owners
This was referenced Jul 18, 2020
twitchy-jsonp
approved these changes
Jul 20, 2020
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This PR is a follow up to the issue #191.
The bug is mainly due to the fact that the old code called
tpmutil.UnpackBufon only one element that issignature.It worked for
RSAsignatures as their corresponding structureTPMS_SIGNATURE_RSASSAcontains only 1 fieldTPM2B_PUBLIC_KEY_RSA, in addition toTPMI_ALG_HASHfield.However, it failed for
ECDSAsignatures because their corresponding structure isTPMS_SIGNATURE_ECDSA,which contains 2 fields R and S - instead of just 1 - which are both
TPM2B_ECC_PARAMETER, in addition toTPMI_ALG_HASHfield.All this information can be found here.
Therefore, the bug can be fixed by calling
tpmutil.UnpackBufon 2 elements, that is R followed by S, in the case ofECDSAsignature, which results in retrieving the whole signature.Signed-off-by: El Mostafa IDRASSI mostafa.idrassi@tutanota.com