pwd_override.c

/*
 * gcc -fPIC -Wall -ldl -shared -o pwd_override.so -Wl,-soname,pwd_override.so pwd_override.c
 */

#define _GNU_SOURCE

#include <pwd.h>
#include <stdio.h>
#include <dlfcn.h>

extern struct passwd *getpwuid(__uid_t __uid) {
    static void *(*my_getpwuid)(__uid_t) = NULL;
    printf("getpwuid %d\n", __uid);
    if (!my_getpwuid)
        my_getpwuid = dlsym(RTLD_NEXT, "getpwuid");
    return my_getpwuid(__uid);
}


extern struct passwd *getpwnam(const char *__name) {
    static void *(*my_getpwnam)(const char *) = NULL;
    printf("getpwnam %s\n", __name);
    if (!my_getpwnam)
        my_getpwnam = dlsym(RTLD_NEXT, "getpwnam");
    return my_getpwnam(__name);
}