use strlcpy & strlcat (#74) * refactor checkpubkeyperms() with safe BSD functions fix gcc8 warnings ``` svr-authpubkey.c: In function 'checkpubkeyperms': svr-authpubkey.c:427:2: warning: 'strncat' specified bound 5 equals source length [-Wstringop-overflow=] strncat(filename, "/.ssh", 5); /* strlen("/.ssh") == 5 */ ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~ svr-authpubkey.c:433:2: warning: 'strncat' specified bound 16 equals source length [-Wstringop-overflow=] strncat(filename, "/authorized_keys", 16); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ``` see https://www.sudo.ws/todd/papers/strlcpy.html * restore strlcpy in xstrdup see original https://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.bin/ssh/xmalloc.c?rev=1.16

#ifndef DBMALLOC_H_
#define DBMALLOC_H_

#include "stdint.h"
#include "stdlib.h"
#include "options.h"

void * m_malloc(size_t size);
void * m_calloc(size_t nmemb, size_t size);
void * m_strdup(const char * str);
void * m_realloc(void* ptr, size_t size);

#if DROPBEAR_TRACKING_MALLOC
void m_free_direct(void* ptr);
void m_malloc_set_epoch(unsigned int epoch);
void m_malloc_free_epoch(unsigned int epoch, int dofree);

#else
/* plain wrapper */
#define m_free_direct free

#endif

#define m_free(X) do {m_free_direct(X); (X) = NULL;} while (0)


#endif /* DBMALLOC_H_ */