libssh2_userauth_publickey_frommemory man page
libssh2_userauth_publickey_frommemory — authenticate a session with a public key, read from memory
int libssh2_userauth_publickey_frommemory(LIBSSH2_SESSION *session, const char *username, size_t username_len, const char *publickeydata, size_t publickeydata_len, const char *privatekeydata, size_t privatekeydata_len, const char *passphrase);
This function allows to authenticate a session with a public key read from memory. It's only supported when libssh2 is backed by OpenSSL. session - Session instance as returned by libssh2_session_init_ex(3)
username - Remote user name to authenticate as.
username_len - Length of username.
publickeydata - Buffer containing the contents of a public key file.
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.
Attempt public key authentication using a PEM encoded private key file stored in memory.
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 isn't really a failure per se.
LIBSSH2_ERROR_ALLOC - An internal memory allocation call failed.
LIBSSH2_ERROR_SOCKET_SEND - Unable to send data on socket.
LIBSSH2_ERROR_PUBLICKEY_UNVERIFIED - The username/public key combination was invalid.
LIBSSH2_ERROR_AUTHENTICATION_FAILED - Authentication using the supplied public key was not accepted.
libssh2_userauth_publickey_frommemory was added in libssh2 1.6.0