WebAuthn-“凭证公共密钥”的字节长度。 [英] WebAuthn - byte length of the "credential public key"

问题描述

在WebAuthn中，身份验证器数据包含可变长度的认证凭据数据，后跟扩展名（如果有）：

In WebAuthn, the authenticator data contains the variable length attested credential data followed by the extensions, if any:

经认证的凭据数据凭据公钥字段而使变量>>。

The attested credential data is made variable because of the credential public key field which is a CBOR map.

如果存在扩展名，如何提前知道此字段的字节长度，以便我可以将该字段截断的不带扩展名传递给CBOR库？

In case there are extensions, how to know in advance the byte length of this field, so that I can pass this field truncated without the extensions to a CBOR library?

我正在使用的CBOR库似乎无法处理额外的字节，而且我对CBOR的了解还不足以知道是否有一个技巧可以根据其第一个字节（或其他任何技巧）来计算映射的字节长度。 / p>

The CBOR library I am using doesn't seem to handle extra bytes, and I don't know CBOR enough to know if there's a trick to compute the byte length of a map from its first bytes (or any other trick).

推荐答案

据我了解，存在无法事先知道，而无需先使用支持额外字节的CBOR解码器（或COSE密钥解析器）来确定凭据公钥数据的终止位置和扩展数据的起始位置。

From what I understand there is no way to know in advance without using a CBOR decoder (or COSE Key parser) supporting "extra bytes" first, to determine where the "credential public key data" ends and where "extension data" starts.

在 WebAuthn 2级草案。

确定经认证的凭据数据的长度，该变量为
涉及到在给定
前面的credentialId的长度的情况下确定credentialPublicKey的起始位置，然后确定
credentialPublicKey的长度（另请参见[RFC8152]的第7节）。

Determining attested credential data's length, which is variable, involves determining credentialPublicKey’s beginning location given the preceding credentialId’s length, and then determining the credentialPublicKey’s length (see also Section 7 of [RFC8152]).

FWIW，也在WebAuthn规范的GitHub问题中进行了讨论， https：// github.com/w3c/webauthn/issues/1012

FWIW, discussed in WebAuthn spec's GitHub issue also https://github.com/w3c/webauthn/issues/1012

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