fido2-cred1

Usage

Overview

fido2-cred makes or verifies a FIDO2 credential.

A credential type may be es256 (denoting ECDSA over NIST P-256 with SHA-256), es384 (denoting ECDSA over NIST P-384 with SHA-384), rs256 (denoting 2048-bit RSA with PKCS#1.5 padding and SHA-256), or eddsa (denoting EDDSA over Curve25519 with SHA-512). If type is not specified, es256 is assumed.

When making a credential, the authenticator may require the user to authenticate with a PIN. If the -q option is not specified, fido2-cred will prompt the user for the PIN. If a tty is available, fido2-cred will use it to obtain the PIN. Otherwise, stdin is used.

The input of fido2-cred is defined by the parameters of the credential to be made/verified. See the INPUT FORMAT section for details.

The output of fido2-cred is defined by the result of the selected operation. See the OUTPUT FORMAT section for details.

If a credential is successfully created or verified, fido2-cred exits 0. Otherwise, fido2-cred exits 1.

The options are as follows:

-M

Tells fido2-cred to make a new credential on device.

-V

Tells fido2-cred to verify a credential.

-b

Request the credential's “largeBlobKey”, a 32-byte symmetric key associated with the generated credential.

-a mode

When making a credential, request enterprise attestation. Please refer to ⟨fido/param.h⟩ for the set of possible values.

-c cred_protect

If making a credential, set the credential's protection level to cred_protect, where cred_protect is the credential's protection level in decimal notation. Please refer to ⟨fido/param.h⟩ for the set of possible values. If verifying a credential, check whether the credential's protection level was signed by the authenticator as cred_protect.

-d

Causes fido2-cred to emit debugging output on stderr.

-h

If making a credential, enable the FIDO2 hmac-secret extension. If verifying a credential, check whether the extension data bit was signed by the authenticator.

-i input_file

Tells fido2-cred to read the parameters of the credential from input_file instead of stdin.

-o output_file

Tells fido2-cred to write output on output_file instead of stdout.

-q

Tells fido2-cred to be quiet. If a PIN is required and -q is specified, fido2-cred will fail.

-r

Create a resident credential. Resident credentials are called “discoverable credentials” in CTAP 2.1.

-t option

Toggles a key/value option, where option is a string of the form “key=value”. The options supported at present are:

uv=true|false

Asks the authenticator for user verification to be enabled or disabled.

pin=true|false

Tells fido2-cred whether to prompt for a PIN and request user verification.

The -t option may be specified multiple times.

-u

Create a U2F credential. By default, fido2-cred will use FIDO2 if supported by the authenticator, and fallback to U2F otherwise.

-v

If making a credential, request user verification. If verifying a credential, check whether the user verification bit was signed by the authenticator.

-w

Tells fido2-cred that the first line of input when making a credential shall be interpreted as unhashed client data. This is required by Windows Hello, which calculates the client data hash internally.

Input format

The input of fido2-cred consists of base64 blobs and UTF-8 strings separated by newline characters ('\n').

When making a credential, fido2-cred expects its input to consist of:

1. client data hash (base64 blob);

2. relying party id (UTF-8 string);

3. user name (UTF-8 string);

4. user id (base64 blob).

When verifying a credential, fido2-cred expects its input to consist of:

1. client data hash (base64 blob);

2. relying party id (UTF-8 string);

3. credential format (UTF-8 string);

4. CBOR encoded authenticator data (base64 blob);

5. credential id (base64 blob);

6. attestation signature (base64 blob);

7. attestation certificate (optional, base64 blob).

UTF-8 strings passed to fido2-cred must not contain embedded newline or NUL characters.

Output format

The output of fido2-cred consists of base64 blobs, UTF-8 strings, and PEM-encoded public keys separated by newline characters ('\n').

Upon the successful generation of a credential, fido2-cred outputs:

1. client data hash (base64 blob);

2. relying party id (UTF-8 string);

3. credential format (UTF-8 string);

4. CBOR encoded authenticator data (base64 blob);

5. credential id (base64 blob);

6. attestation signature (base64 blob);

7. attestation certificate, if present (base64 blob).

8. the credential's associated 32-byte symmetric key (“largeBlobKey”), if present (base64 blob).

Upon the successful verification of a credential, fido2-cred outputs:

1. credential id (base64 blob);

2. PEM-encoded credential key.

Examples

Create a new es256 credential on /dev/hidraw5, verify it, and save the id and the public key of the credential in cred:

$ echo credential challenge | openssl sha256 -binary | base64 > cred_param

$ echo relying party >> cred_param

$ echo user name >> cred_param

$ dd if=/dev/urandom bs=1 count=32 | base64 >> cred_param

$ fido2-cred -M -i cred_param /dev/hidraw5 | fido2-cred -V -o cred

Caveats

Please note that fido2-cred handles Basic Attestation and Self Attestation transparently. In the case of Basic Attestation, the validity of the authenticator's attestation certificate is not verified.