External Public-Key Authentication API (#72) * Implemented dynamic loading of an external plug-in shared library to delegate public key authentication * Moved conditional compilation of the plugin infrastructure into the configure.ac script to be able to add -ldl to dropbear build only when the flag is enabled * Added tags file to the ignore list * Updated API to have the constructor to return function pointers in the pliugin instance. Added support for passing user name to the checkpubkey function. Added options to the session returned by the plugin and have dropbear to parse and process them * Added -rdynamic to the linker flags when EPKA is enabled * Changed the API to pass a previously created session to the checkPubKey function (created during preauth) * Added documentation to the API * Added parameter addrstring to plugin creation function * Modified the API to retrieve the auth options. Instead of having them as field of the EPKASession struct, they are stored internally (plugin-dependent) in the plugin/session and retrieved through a pointer to a function (in the session) * Changed option string to be a simple char * instead of unsigned char *

#ifndef DROPBEAR_DROPBEAR_ECC_H
#define DROPBEAR_DROPBEAR_ECC_H

#include "includes.h"

#include "buffer.h"

#if DROPBEAR_ECC

struct dropbear_ecc_curve {
	int ltc_size; /* to match the byte sizes in ltc_ecc_sets[] */
	const ltc_ecc_set_type *dp; /* curve domain parameters */
	const struct ltc_hash_descriptor *hash_desc;
	const char *name;
};

extern struct dropbear_ecc_curve ecc_curve_nistp256;
extern struct dropbear_ecc_curve ecc_curve_nistp384;
extern struct dropbear_ecc_curve ecc_curve_nistp521;
extern struct dropbear_ecc_curve *dropbear_ecc_curves[];

void dropbear_ecc_fill_dp(void);
struct dropbear_ecc_curve* curve_for_dp(const ltc_ecc_set_type *dp);

/* "pubkey" refers to a point, but LTC uses ecc_key structure for both public
   and private keys */
void buf_put_ecc_raw_pubkey_string(buffer *buf, ecc_key *key);
ecc_key * buf_get_ecc_raw_pubkey(buffer *buf, const struct dropbear_ecc_curve *curve);
int buf_get_ecc_privkey_string(buffer *buf, ecc_key *key);

mp_int * dropbear_ecc_shared_secret(ecc_key *pub_key, const ecc_key *priv_key);

#endif

#endif /* DROPBEAR_DROPBEAR_ECC_H */