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FIDO2-ASSERT(1)             General Commands Manual            FIDO2-ASSERT(1)

NAME
     fido2-assert - get/verify a FIDO2 assertion

SYNOPSIS
     fido2-assert -G [-bdhpruv] [-t option] [-i input_file] [-o output_file]
                  device
     fido2-assert -V [-dhpv] [-i input_file] key_file [type]

DESCRIPTION
     fido2-assert gets or verifies a FIDO2 assertion.

     The input of fido2-assert is defined by the parameters of the assertion
     to be obtained/verified.  See the INPUT FORMAT section for details.

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

     If an assertion is successfully obtained or verified, fido2-assert exits
     0.  Otherwise, fido2-assert exits 1.

     The options are as follows:

     -G      Tells fido2-assert to obtain a new assertion from device.

     -V      Tells fido2-assert to verify an assertion using the PEM-encoded
             public key in key_file of type type, where 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.

     -b      Request the credential's "largeBlobKey", a 32-byte symmetric key
             associated with the asserted credential.

     -h      If obtaining an assertion, enable the FIDO2 hmac-secret
             extension.  If verifying an assertion, check whether the
             extension data bit was signed by the authenticator.

     -d      Causes fido2-assert to emit debugging output on stderr.

     -i input_file
             Tells fido2-assert to read the parameters of the assertion from
             input_file instead of stdin.

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

     -p      If obtaining an assertion, request user presence.  If verifying
             an assertion, check whether the user presence bit was signed by
             the authenticator.

     -r      Obtain an assertion using a resident credential.  If -r is
             specified, fido2-assert will not expect a credential id in its
             input, and may output multiple assertions.  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:

             up=true|false
                     Asks the authenticator for user presence to be enabled or
                     disabled.

             uv=true|false
                     Asks the authenticator for user verification to be
                     enabled or disabled.

             pin=true|false
                     Tells fido2-assert whether to prompt for a PIN and
                     request user verification.

             The -t option may be specified multiple times.

     -u      Obtain an assertion using U2F.  By default, fido2-assert will use
             FIDO2 if supported by the authenticator, and fallback to U2F
             otherwise.

     -v      If obtaining an assertion, prompt the user for a PIN and request
             user verification from the authenticator.  If verifying an
             assertion, check whether the user verification bit was signed by
             the authenticator.

     If a tty is available, fido2-assert will use it to obtain the PIN.
     Otherwise, stdin is used.

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

     When obtaining an assertion, fido2-assert expects its input to consist
     of:

           1.   client data hash (base64 blob);
           2.   relying party id (UTF-8 string);
           3.   credential id, if credential not resident (base64 blob);
           4.   hmac salt, if the FIDO2 hmac-secret extension is enabled
                (base64 blob);

     When verifying an assertion, fido2-assert expects its input to consist
     of:

           1.   client data hash (base64 blob);
           2.   relying party id (UTF-8 string);
           3.   authenticator data (base64 blob);
           4.   assertion signature (base64 blob);

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

OUTPUT FORMAT
     The output of fido2-assert consists of base64 blobs and UTF-8 strings
     separated by newline characters ('\n').

     For each generated assertion, fido2-assert outputs:

           1.   client data hash (base64 blob);
           2.   relying party id (UTF-8 string);
           3.   authenticator data (base64 blob);
           4.   assertion signature (base64 blob);
           5.   user id, if credential resident (base64 blob);
           6.   hmac secret, if the FIDO2 hmac-secret extension is enabled
                (base64 blob);
           7.   the credential's associated 32-byte symmetric key
                ("largeBlobKey"), if requested (base64 blob).

     When verifying an assertion, fido2-assert produces no output.

EXAMPLES
     Assuming cred contains a es256 credential created according to the steps
     outlined in fido2-cred(1), obtain an assertion from an authenticator at
     /dev/hidraw5 and verify it:

           $ echo assertion challenge | openssl sha256 -binary | base64 >
           assert_param
           $ echo relying party >> assert_param
           $ head -1 cred >> assert_param
           $ tail -n +2 cred > pubkey
           $ fido2-assert -G -i assert_param /dev/hidraw5 | fido2-assert -V
           pubkey es256

SEE ALSO
     fido2-cred(1), fido2-token(1)

NetBSD 10.99             $Mdocdate: November 5 2019 $             NetBSD 10.99