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libssh2_userauth_publickey_sk(3)    libssh2   libssh2_userauth_publickey_sk(3)

NAME
       libssh2_userauth_publickey_sk - authenticate a session with a FIDO2
       authenticator

SYNOPSIS
       #include <libssh2.h>

       int
       libssh2_userauth_publickey_sk(LIBSSH2_SESSION *session,
                                     const char *username,
                                     size_t username_len,
                                     const unsigned char *publickeydata,
                                     size_t publickeydata_len,
                                     const char *privatekeydata,
                                     size_t privatekeydata_len,
                                     const char *passphrase,
                                     LIBSSH2_USERAUTH_SK_SIGN_FUNC((*sign_callback)),
                                     void **abstract);

CALLBACK
       #define LIBSSH2_SK_PRESENCE_REQUIRED     0x01
       #define LIBSSH2_SK_VERIFICATION_REQUIRED 0x04

       typedef struct _LIBSSH2_SK_SIG_INFO {
           uint8_t flags;
           uint32_t counter;
           unsigned char *sig_r;
           size_t sig_r_len;
           unsigned char *sig_s;
           size_t sig_s_len;
       } LIBSSH2_SK_SIG_INFO;

       int name(LIBSSH2_SESSION *session, LIBSSH2_SK_SIG_INFO *sig_info,
                const unsigned char *data, size_t data_len, int algorithm,
                uint8_t flags, const char *application,
                const unsigned char *key_handle, size_t handle_len,
                void **abstract);

DESCRIPTION
       session - Session instance as returned by libssh2_session_init_ex(3)

       username - Name of user to attempt authentication for.

       username_len - Length of username parameter.

       publickeydata - Buffer containing the contents of a public key file. If
       NULL, the public key will be extracted from the privatekeydata. When
       using certificate authentication, this buffer should contain the public
       certificate data.

       publickeydata_len - Length of public key data.

       privatekeydata - Buffer containing the contents of a private key file.

       privatekeydata_len - Length of private key data.

       passphrase - Passphrase to use when decoding private key file.

       sign_callback - Callback to communicate with FIDO2 authenticator.

       abstract - User-provided data to pass to callback.

       Attempt FIDO2 authentication. using either the sk-ssh-
       ed25519@openssh.com or sk-ecdsa-sha2-nistp256@openssh.com key exchange
       algorithms.

       This function is only supported when libssh2 is backed by OpenSSL.

CALLBACK DESCRIPTION
       session - Session instance as returned by libssh2_session_init_ex(3)

       sig_info - Filled in by the callback with the signature and
       accompanying information from the authenticator.

       data - The data to sign.

       data_len - The length of the data parameter.

       algorithm - The signing algorithm to use. Possible values are
       LIBSSH2_HOSTKEY_TYPE_ED25519 and LIBSSH2_HOSTKEY_TYPE_ECDSA_256.

       flags - A bitmask specifying options for the authenticator. When
       LIBSSH2_SK_PRESENCE_REQUIRED is set, the authenticator requires a
       touch. When LIBSSH2_SK_VERIFICATION_REQUIRED is set, the authenticator
       requires a PIN.  Many servers and authenticators do not work properly
       when LIBSSH2_SK_PRESENCE_REQUIRED is not set.

       application - A user-defined string to use as the RP name for the
       authenticator. Usually "ssh:".

       key_handle - The key handle to use for the authenticator's allow list.

       handle_len - The length of the key_handle parameter.

       abstract - User-defined data. When a PIN is required, use this to pass
       in the PIN, or a function pointer to retrieve the PIN.

       The sign_callback is responsible for communicating with the hardware
       authenticator to generate a signature. On success, the signature
       information must be placed in the `sig_info sig_info parameter and the
       callback must return 0. On failure, it should return a negative number.

       The fields of the LIBSSH2_SK_SIG_INFO are as follows.

       flags - A bitmask specifying options for the authenticator. This should
       be read from the authenticator and not merely copied from the flags
       parameter to the callback.

       counter - A value returned from the authenticator.

       sig_r - For Ed25519 signatures, this contains the entire signature, as
       returned directly from the authenticator. For ECDSA signatures, this
       contains the r component of the signature in a big-endian binary
       representation. For both algorithms, use LIBSSH2_ALLOC to allocate
       memory. It will be freed by the caller.

       sig_r_len - The length of the sig_r parameter.

       sig_s - For ECDSA signatures, this contains the s component of the
       signature in a big-endian binary representation. Use LIBSSH2_ALLOC to
       allocate memory. It will be freed by the caller. For Ed25519
       signatures, set this to NULL.

       sig_s_len - The length of the sig_s parameter.

RETURN VALUE
       Return 0 on success or negative on failure. It returns
       LIBSSH2_ERROR_EAGAIN when it would otherwise block. While
       LIBSSH2_ERROR_EAGAIN is a negative number, it is not really a failure
       per se.

ERRORS
       Some of the errors this function may return include:

       LIBSSH2_ERROR_ALLOC - An internal memory allocation call failed.

       LIBSSH2_ERROR_SOCKET_SEND - Unable to send data on socket.

       LIBSSH2_ERROR_AUTHENTICATION_FAILED - failed, invalid username/key.

AVAILABILITY
       Added in libssh2 1.10.0

SEE ALSO
       libssh2_session_init_ex(3)

libssh2                           1 Jun 2022  libssh2_userauth_publickey_sk(3)