/* $OpenBSD: crunchide.c,v 1.12 2017/10/29 08:45:53 mpi 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/mman.h>
#include <sys/stat.h>

#include <elf.h>
#include <fcntl.h>
#include <stdint.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) || infstat.st_size > SIZE_MAX) {
                fprintf(stderr, "%s: invalid file size\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);
}