63 lines
1.5 KiB
C
63 lines
1.5 KiB
C
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/* This file is part of the sample code and exercises
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* used by the class "Advanced Programming in the UNIX
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* Environment" taught by Jan Schaumann
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* <jschauma@netmeister.org> at Stevens Institute of
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* Technology.
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*
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* This file is in the public domain.
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*
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* You don't have to, but if you feel like
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* acknowledging where you got this code, you may
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* reference me by name, email address, or point
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* people to the course website:
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* https://stevens.netmeister.org/631/
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*/
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/* This program can be used to illustrate that we can load symbols from
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* dynamic libraries at runtime without actually linking against them.
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*
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* Note that we do _not_ link against libcrypt, nor do we include the
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* unistd.h header.
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*
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* cc -Wall -Werror -Wextra crypt.c
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* cc -Wall -Werror -Wextra -rdynamic dlopenex.c
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*/
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#include <err.h>
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#include <errno.h>
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#include <dlfcn.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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void
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printCrypt(const char *s) {
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void *dlhandle;
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char *(*_crypt)(const char *, const char *);
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char *error;
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dlhandle = dlopen("libcrypt.so", RTLD_LAZY);
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if (!dlhandle) {
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err(EXIT_FAILURE, "%s\n", dlerror());
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/* NOTREACHED */
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}
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*(void **) (&_crypt) = dlsym(dlhandle, "crypt");
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if ((error = dlerror()) != NULL) {
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err(EXIT_FAILURE, "%s\n", error);
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/* NOTREACHED */
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}
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(void)printf("%s\n", _crypt(s, "$1"));
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}
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int
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main(int argc, char **argv) {
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if (argc != 2) {
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(void)fprintf(stderr, "Usage: %s string\n", argv[0]);
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exit(EXIT_FAILURE);
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}
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printCrypt(argv[1]);
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exit(EXIT_SUCCESS);
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}
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