libssh2_userauth_publickey_sk - authenticate a session with a FIDO2 authenticator
#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);
#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);
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.
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 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.
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.
Added in libssh2 1.10.0
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