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/* $OpenBSD: crunchide.c,v 1.10 2015/08/20 22:39:29 deraadt Exp $ */
/*
* Copyright (c) 1994 University of Maryland
* All Rights Reserved.
*
* Permission to use, copy, modify, distribute, and sell this software and its
* documentation for any purpose is hereby granted without fee, provided that
* the above copyright notice appear in all copies and that both that
* copyright notice and this permission notice appear in supporting
* documentation, and that the name of U.M. not be used in advertising or
* publicity pertaining to distribution of the software without specific,
* written prior permission. U.M. makes no representations about the
* suitability of this software for any purpose. It is provided "as is"
* without express or implied warranty.
*
* U.M. DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL U.M.
* BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
* OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
* CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*
* Author: James da Silva, Systems Design and Analysis Group
* Computer Science Department
* University of Maryland at College Park
*/
/*
* crunchide.c - tiptoes through an a.out symbol table, hiding all defined
* global symbols. Allows the user to supply a "keep list" of symbols
* that are not to be hidden. This program relies on the use of the
* linker's -dc flag to actually put global bss data into the file's
* bss segment (rather than leaving it as undefined "common" data).
*
* The point of all this is to allow multiple programs to be linked
* together without getting multiple-defined errors.
*
* For example, consider a program "foo.c". It can be linked with a
* small stub routine, called "foostub.c", eg:
* int foo_main(int argc, char **argv){ return main(argc, argv); }
* like so:
* cc -c foo.c foostub.c
* ld -dc -r foo.o foostub.o -o foo.combined.o
* crunchide -k _foo_main foo.combined.o
* at this point, foo.combined.o can be linked with another program
* and invoked with "foo_main(argc, argv)". foo's main() and any
* other globals are hidden and will not conflict with other symbols.
*
* TODO:
* - arrange that all the BSS segments start at the same address, so
* that the final crunched binary BSS size is the max of all the
* component programs' BSS sizes, rather than their sum.
*/
#include <sys/types.h>
#include <sys/exec_elf.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include "mangle.h"
void usage(void);
void add_to_keep_list(char *);
void add_file_to_keep_list(char *);
void hide_syms(char *);
void elf_hide(int, char *);
int in_keep_list(char *symbol);
int crunchide_main(int argc, char *argv[]);
extern char *__progname;
extern int elf_mangle;
int
crunchide_main(int argc, char *argv[])
{
int ch;
while ((ch = getopt(argc, argv, "Mhk:f:")) != -1)
switch (ch) {
case 'M':
elf_mangle = 1;
break;
case 'h':
break;
case 'k':
add_to_keep_list(optarg);
break;
case 'f':
add_file_to_keep_list(optarg);
break;
default:
usage();
}
argc -= optind;
argv += optind;
if (argc == 0)
usage();
if (elf_mangle)
init_mangle_state();
while (argc) {
hide_syms(*argv);
argc--;
argv++;
}
if (elf_mangle)
fini_mangle_state();
return 0;
}
struct keep {
struct keep *next;
char *sym;
} *keep_list;
void
add_to_keep_list(char *symbol)
{
struct keep *newp, *prevp, *curp;
int cmp = 0;
for (curp = keep_list, prevp = NULL; curp; prevp = curp, curp = curp->next)
if ((cmp = strcmp(symbol, curp->sym)) <= 0)
break;
if (curp && cmp == 0)
return; /* already in table */
newp = calloc(1, sizeof(struct keep));
if (newp)
newp->sym = strdup(symbol);
if (newp == NULL || newp->sym == NULL) {
fprintf(stderr, "%s: out of memory for keep list\n", __progname);
exit(1);
}
newp->next = curp;
if (prevp)
prevp->next = newp;
else
keep_list = newp;
}
int
in_keep_list(char *symbol)
{
struct keep *curp;
int cmp = 0;
for (curp = keep_list; curp; curp = curp->next)
if ((cmp = strcmp(symbol, curp->sym)) <= 0)
break;
return curp && cmp == 0;
}
void
add_file_to_keep_list(char *filename)
{
FILE *keepf;
char symbol[1024];
int len;
if ((keepf = fopen(filename, "r")) == NULL) {
perror(filename);
usage();
}
while (fgets(symbol, sizeof(symbol), keepf)) {
len = strlen(symbol);
if (len && symbol[len - 1] == '\n')
symbol[len - 1] = '\0';
add_to_keep_list(symbol);
}
fclose(keepf);
}
void
hide_syms(char *filename)
{
int inf;
struct stat infstat;
char *buf;
/*
* Open the file and do some error checking.
*/
if ((inf = open(filename, O_RDWR)) == -1) {
perror(filename);
return;
}
if (fstat(inf, &infstat) == -1) {
perror(filename);
close(inf);
return;
}
if (infstat.st_size < sizeof(Elf_Ehdr)) {
fprintf(stderr, "%s: short file\n", filename);
close(inf);
return;
}
if ((buf = mmap(NULL, infstat.st_size, PROT_READ | PROT_WRITE,
MAP_FILE | MAP_SHARED, inf, 0)) == MAP_FAILED) {
fprintf(stderr, "%s: cannot map\n", filename);
close(inf);
return;
}
if (buf[0] == ELFMAG0 && buf[1] == ELFMAG1 &&
buf[2] == ELFMAG2 && buf[3] == ELFMAG3) {
elf_hide(inf, buf);
return;
}
close(inf);
}
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