libssh2_sign_sk(3)

💖 libssh2_sign_sk 💖

okay bestie, so this is a page from the libssh2 manual set — it's libssh2_sign_sk, and it's all about getting a signature out of your FIDO2 authenticator. yes, the little key you boop with your finger. iconic behaviour honestly. let's get into it 🫶

✨ NAME ✨

libssh2_sign_sk — Create a signature from a FIDO2 authenticator.

✨ SYNOPSIS ✨

#include <libssh2.h>

int
libssh2_sign_sk(LIBSSH2_SESSION *session,
                unsigned char **sig,
                size_t *sig_len,
                const unsigned char *data,
                size_t data_len,
                void **abstract);

typedef struct _LIBSSH2_PRIVKEY_SK {
    int algorithm;
    uint8_t flags;
    const char *application;
    const unsigned char *key_handle;
    size_t handle_len;
    LIBSSH2_USERAUTH_SK_SIGN_FUNC((*sign_callback));
    void **orig_abstract;
} LIBSSH2_PRIVKEY_SK;

✨ DESCRIPTION ✨

okay so here's the vibe — every single one of these parameters, explained with love 💜

• session — Session instance as returned by libssh2_session_init_ex(3). that's your main character session object fr fr.
• sig — A pointer to a buffer in which to place the signature. The caller is responsible for freeing the signature with LIBSSH2_FREE. yes bestie, you have to clean up after yourself, it's giving chores.
• sig_len — A pointer to the length of the sig parameter.
• data — The data to sign.
• data_len — The length of the data parameter.
• abstract — A pointer to a pointer to a LIBSSH2_PRIVKEY_SK. See description below. 👀

Create a signature from a FIDO2 authenticator, using either the sk-ssh-ed25519@openssh.com or sk-ecdsa-sha2-nistp256@openssh.com key exchange algorithms. pick your fighter, both ate. 🎀

The abstract parameter is a pointer to a pointer due to the internal workings of libssh2. The LIBSSH2_PRIVKEY_SK must be completely filled out, and the caller is responsible for all memory management of its fields. no skipping fields, no cap — fill it all in and manage your own memory, that's the deal.

• 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. 🫵 so like, set it. please. for your own good.
• 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.
• key_handle The decoded key handle from the private key file.
• handle_len The length of the key_handle parameter.
• sign_callback — 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. See libssh2_userauth_publickey_sk(3) for more information. ✨
• orig_abstract — User-defined data. When a PIN is required, use this to pass in the PIN, or a function pointer to retrieve the PIN.

✨ RETURN VALUE ✨

Return 0 on success or negative on failure. that's it, that's the whole mood 💅

✨ SEE ALSO ✨

• libssh2_userauth_publickey_sk(3)

and that's a wrap, bestie 🌈 this lil page is from the libssh2 1.10.0 era, dated 1 Jun 2022. go forth, boop your authenticator, and slay 👑💖