main.c

/*
    Scanmem main function, option parsing and help text.

    Copyright (C) 2006,2007,2009 Tavis Ormandy <taviso@sdf.lonestar.org>
    Copyright (C) 2009           Eli Dupree <elidupree@charter.net>
    Copyright (C) 2009-2013      WANG Lu <coolwanglu@gmail.com>
    Copyright (C) 2016           Sebastian Parschauer <s.parschauer@gmx.de>

    This file is part of scanmem.
 
    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#ifndef _GNU_SOURCE
#define _GNU_SOURCE
#endif

#include "config.h"

#include <errno.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <getopt.h>
#include <stdbool.h>

#include <pwd.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/types.h>

#if HAVE_LIBREADLINE
# include <readline/history.h>
#else
# include "readline.h"
#endif

#include "common.h"
#include "scanmem.h"
#include "commands.h"
#include "show_message.h"

#include "menu.h"


static const char copy_text[] =
"Copyright (C) 2006-2017 Scanmem authors\n"
"See https://github.com/scanmem/scanmem/blob/master/AUTHORS for a full author list\n"
"\n"
"scanmem comes with ABSOLUTELY NO WARRANTY; for details type `show warranty'.\n"
"This is free software, and you are welcome to redistribute it\n"
"under certain conditions; type `show copying' for details.\n\n";

/* print scanmem and libscanmem version */
static void printversion(FILE *outfd)
{
    fprintf(outfd, "scanmem version %s\n", PACKAGE_VERSION);
    sm_printversion(outfd);
}

/* print scanmem version and copyright info */
static void printcopyright(FILE *outfd)
{
    printversion(outfd);
    fprintf(outfd, "\n%s", copy_text);
}

static const char help_text[] =
"Usage: scanmem [OPTION]... [PID]\n"
"Interactively locate and modify variables in an executing process.\n"
"\n"
"-p, --pid=pid\t\tset the target process pid\n"
"-c, --command\t\trun given commands (separated by `;`)\n"
"-h, --help\t\tprint this message\n"
"-v, --version\t\tprint version information\n"
"\n"
"scanmem is an interactive debugging utility, enter `help` at the prompt\n"
"for further assistance.\n"
"\n"
"Report bugs to <" PACKAGE_BUGREPORT ">.\n";

/* print quick usage message to stderr */
static void printhelp(void)
{
    printcopyright(stderr);

    show_user("%s", help_text);
    return;
}

static inline void show_user_quick_help(pid_t target)
{
    if (target == 0) {
        show_user("Enter the pid of the process to search using the \"pid\" command.\n");
        show_user("Enter \"help\" for other commands.\n");
    } else {
        show_user("Please enter current value, or \"help\" for other commands.\n");
    }
}

static inline char *get_config_dir(void)
{
    /*
     * Try to find our config folder in order:
     * - XDG config dir
     * - $HOME/.config
     * - <system-given home>/.config
     *
     * In normal cases the dir will end up being: $HOME/.config/scanmem
     */

    char *sm_config_dir;

    const char *config_dir = util_getenv("XDG_CONFIG_HOME");
    if (config_dir == NULL) {
        const char *home_dir = util_getenv("HOME");
        if (home_dir == NULL) {
            home_dir = getpwuid(getuid())->pw_dir;
        }

        size_t sm_config_dir_len = strlen(home_dir) + strlen("/.config/scanmem") + 1;
        sm_config_dir = malloc(sm_config_dir_len * sizeof(char));
        if (sm_config_dir == NULL)
            return NULL;
        snprintf(sm_config_dir, sm_config_dir_len, "%s/.config/scanmem", home_dir);
    }
    else {
        size_t sm_config_dir_len = strlen(config_dir) + strlen("/scanmem") + 1;
        sm_config_dir = malloc(sm_config_dir_len * sizeof(char));
        if (sm_config_dir == NULL)
            return NULL;
        snprintf(sm_config_dir, sm_config_dir_len, "%s/scanmem", config_dir);
    }

    return sm_config_dir;
}

/* Recursive `mkdir()` implementation, from
 * https://stackoverflow.com/a/9210960/3288954
 * Takes a full file path as input */
static inline int mkpath(const char *file_path, mode_t mode)
{
    assert(file_path != NULL);
    char* p;
    for (p = strchr(file_path + 1, '/'); p != NULL; p = strchr(p + 1, '/')) {
        *p = '\0';
        if (mkdir(file_path, mode) == -1 && errno != EEXIST) {
            *p='/';
            return -1;
        }
        *p = '/';
    }
    return 0;
}

static void parse_parameters(int argc, char **argv, char **initial_commands, bool *exit_on_error)
{
    struct option longopts[] = {
        {"pid",     1, NULL, 'p'},      /* target pid */
        {"command", 1, NULL, 'c'},      /* commands to run at the beginning */
        {"version", 0, NULL, 'v'},      /* print version */
        {"help",    0, NULL, 'h'},      /* print help summary */
        {"debug",   0, NULL, 'd'},      /* enable debug mode */
        {"errexit", 0, NULL, 'e'},      /* exit on initial command failure */
        {NULL, 0, NULL, 0},
    };
    char *end;
    int optindex;
    bool done = false;
    globals_t *vars = &sm_globals;

    /* process command line */
    while (!done) {
        switch (getopt_long(argc, argv, "vhdep:c:", longopts, &optindex)) {
            case 'p':
                vars->target = (pid_t) strtoul(optarg, &end, 0);

                /* check if that parsed correctly */
                if (*end != '\0' || *optarg == '\0' || vars->target == 0) {
                    show_error("invalid pid specified.\n");
                    exit(EXIT_FAILURE);
                }
                break;
            case 'c':
                *initial_commands = optarg;
                break;
            case 'v':
                printversion(stderr);
                exit(EXIT_FAILURE);
            case 'h':
                printhelp();
                exit(EXIT_FAILURE);
            case 'd':
                vars->options.debug = 1;
                break;
            case 'e':
                *exit_on_error = true;
                break;
            case -1:
                done = true;
                break;
            default:
                printhelp();
                exit(EXIT_FAILURE);
        }
    }
    /* parse any pid specified after arguments */
    if (optind <= argc && argv[optind]) {
        vars->target = (pid_t) strtoul(argv[optind], &end, 0);

        /* check if that parsed correctly */
        if (*end != '\0' || argv[optind][0] == '\0' || vars->target == 0) {
            show_error("invalid pid specified.\n");
            exit(EXIT_FAILURE);
        }
    }
}

int main(int argc, char **argv)
{
    char *initial_commands = NULL;
    bool exit_on_error = false;
    parse_parameters(argc, argv, &initial_commands, &exit_on_error);

    int ret = EXIT_SUCCESS;
    globals_t *vars = &sm_globals;

    printcopyright(stderr);
    vars->printversion = printversion;

    if (!sm_init()) {
        show_error("Initialization failed.\n");
        ret = EXIT_FAILURE;
        goto end;
    }

    if (getuid() != 0) {
        show_warn("Run scanmem as root if memory regions are missing. "
                  "See scanmem man page.\n\n");
    }

    /* this will initialize matches and regions */
    if (sm_execcommand(vars, "reset") == false) {
        vars->target = 0;
    }

    /* check if there is a target already specified */
    show_user_quick_help(vars->target);

    /* execute commands passed by `-c`, if any */
    if (initial_commands) {
        char *saveptr = NULL;
        const char sep[] = ";\n";
        for (char *line = strtok_r(initial_commands, sep, &saveptr);
             line != NULL; line = strtok_r(NULL, sep, &saveptr))
        {
            if (vars->matches) {
                show_user("%ld> %s\n", vars->num_matches, line);
            } else {
                show_user("> %s\n", line);
            }

            if (sm_execcommand(vars, line) == false) {
                if (exit_on_error) goto end;
                show_user_quick_help(vars->target);
            }

            fflush(stdout);
            fflush(stderr);
        }
    }
    if (vars->exit)
        goto end;

    /* Start of interactive mode: recover history from history file */
    const unsigned int hist_max_size = 1000;
    char *sm_config_dir = get_config_dir();
    if (sm_config_dir == NULL) {
        show_error("Couldn't allocate memory");
        goto end;
    }

    size_t hist_file_len = strlen(sm_config_dir) + strlen("/history") + 1;
    char * hist_file = malloc(hist_file_len * sizeof(char));
    if (hist_file == NULL) {
        show_error("Couldn't allocate memory");
        goto end;
    }
    snprintf(hist_file, hist_file_len, "%s/history", sm_config_dir);
    free(sm_config_dir);

    read_history(hist_file);

    /* main loop, read input and process commands */
    while (true) {
        char *line;

        /* reads in a commandline from the user and returns a pointer to it in *line */
        if (getcommand(vars, &line) == false) {
            show_error("failed to read in a command.\n");
            ret = EXIT_FAILURE;
            break;
        }

        /* sm_execcommand() returning failure is not fatal, it just means the command could not complete. */
        if (sm_execcommand(vars, line) == false) {
            show_user_quick_help(vars->target);
        }

        free(line);

        fflush(stdout);
        fflush(stderr);

        if (vars->exit) {
            /* write history: create directory if needed.
             * Permissions used are mandated by the FD spec:
             * https://standards.freedesktop.org/basedir-spec/latest/ar01s04.html
             */
            if (mkpath(hist_file, 0700) == 0) {
                write_history(hist_file);
                history_truncate_file(hist_file, hist_max_size);
            }
            free(hist_file);
            break;
        }
    }

end:
    sm_cleanup();
    return ret;
}