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_ECDSA_H_
#define DROPBEAR_ECDSA_H_

#include "includes.h"
#include "buffer.h"
#include "signkey.h"

#if DROPBEAR_ECDSA

/* prefer 256 or 384 since those are SHOULD for
   draft-ietf-curdle-ssh-kex-sha2.txt */
#if DROPBEAR_ECC_256
#define ECDSA_DEFAULT_SIZE 256
#elif DROPBEAR_ECC_384
#define ECDSA_DEFAULT_SIZE 384
#elif DROPBEAR_ECC_521
#define ECDSA_DEFAULT_SIZE 521
#else
#error ECDSA cannot be enabled without enabling at least one size (256, 384, 521)
#endif

ecc_key *gen_ecdsa_priv_key(unsigned int bit_size);
ecc_key *buf_get_ecdsa_pub_key(buffer* buf);
ecc_key *buf_get_ecdsa_priv_key(buffer *buf);
void buf_put_ecdsa_pub_key(buffer *buf, ecc_key *key);
void buf_put_ecdsa_priv_key(buffer *buf, ecc_key *key);
enum signkey_type ecdsa_signkey_type(const ecc_key * key);

void buf_put_ecdsa_sign(buffer *buf, const ecc_key *key, const buffer *data_buf);
int buf_ecdsa_verify(buffer *buf, const ecc_key *key, const buffer *data_buf);
/* Returns 1 on success */
int signkey_is_ecdsa(enum signkey_type type);

#endif

#endif /* DROPBEAR_ECDSA_H_ */