fido2-cred — make/verify a FIDO2 credential
Contents
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.
Debian July 3, 2023 FIDO2-CRED(1)
Description
fido2-cred makes or verifies a FIDO2 credential.
A credential type may be es256 (denoting ECDSA over NIST P-256 with SHA-256), 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.
-ccred_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.
-iinput_file
Tells fido2-cred to read the parameters of the credential from input_file instead of stdin.
-ooutput_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.
-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.
Examples
Create a new es256 credential on /dev/hidraw5, verify it, and save the id and the public key of the
credential in cred:
$echocredentialchallenge | opensslsha256-binary | base64>cred_param$echorelyingparty>>cred_param$echousername>>cred_param$ddif=/dev/urandombs=1count=32 | base64>>cred_param$fido2-cred-M-icred_param/dev/hidraw5 | fido2-cred-V-ocredInput 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. 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.
Name
fido2-cred — make/verify a FIDO2 credential
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. 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.
See Also
fido2-assert(1), fido2-token(1)
Synopsis
fido2-cred-M [-bdhqruvw] [-ccred_protect] [-iinput_file] [-ooutput_file] device [type]
fido2-cred-V [-dhv] [-ccred_protect] [-iinput_file] [-ooutput_file] [type]
