help with get assertion response

[Levi]

hi team,

so i've managed to register with make credential response using es256 keys.

now i'm trying to authenticate through get assertion request and i'm unable to authnticate.

what i know by now is that i should send an  PublicKeyCredentialDescriptor that signs the challenge let's say mine looks like this:

{id: [16, 166, 234, 146, 19, 201, 116, 47, 116, 178, 34, 146, 179, 32, 207, 64], type: public-key}

and authData let's saymine looks like this:

[16, 166, 234, 146, 19, 201, 116, 47, 116, 178, 34, 146, 179, 32, 207, 64 , 38, 42, 148, 193, 169, 80, 160, 57, 127, 41, 37, 11, 96, 132, 30, 240, 29, 0, 0, 0, 0]

(32 first bytes are rpid hash then 1 byte of flags and last 4 bytes are signCounter as its the first getAssertion)
and signature of authData || clientDataHash ( || for concat operation).

my question is as follows:
1. should i hash (authData || clientDataHash) before signing?
2. what is the signature format? is it R || S? is it DER?

cause for now i'm unable to authenticate and i don't know what am i doing wrong.

[Adam Langley]

On Thursday, September 14, 2023 at 1:07:55 AM UTC-7 Levi wrote:

hi team,

so i've managed to register with make credential response using es256 keys.

now i'm trying to authenticate through get assertion request and i'm unable to authnticate.

what i know by now is that i should send an  PublicKeyCredentialDescriptor that signs the challenge let's say mine looks like this:

{id: [16, 166, 234, 146, 19, 201, 116, 47, 116, 178, 34, 146, 179, 32, 207, 64], type: public-key}

and authData let's saymine looks like this:

[16, 166, 234, 146, 19, 201, 116, 47, 116, 178, 34, 146, 179, 32, 207, 64 , 38, 42, 148, 193, 169, 80, 160, 57, 127, 41, 37, 11, 96, 132, 30, 240, 29, 0, 0, 0, 0]

(32 first bytes are rpid hash then 1 byte of flags and last 4 bytes are signCounter as its the first getAssertion)
and signature of authData || clientDataHash ( || for concat operation).

my question is as follows:
1. should i hash (authData || clientDataHash) before signing?

The signature scheme should do the internally.

 

2. what is the signature format? is it R || S? is it DER?

DER.

Cheers

AGL