appimagetool.c

/**************************************************************************
 * 
 * Copyright (c) 2004-17 Simon Peter
 * 
 * All Rights Reserved.
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 * 
 **************************************************************************/

#ident "AppImage by Simon Peter, http://appimage.org/"

#include <glib.h>
#include <glib/gstdio.h>
#include <stdlib.h>

#include <stdio.h>
#include <argp.h>

#include <stdlib.h>
#include <fcntl.h>
#include "squashfuse.h"

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/wait.h>

#include "binreloc.h"

#include <libgen.h>

#include <unistd.h>
#include <string.h>

#include "elf.h"
#include "getsection.h"

extern int _binary_runtime_start;
extern int _binary_runtime_end;


static gboolean list = FALSE;
static gboolean verbose = FALSE;
static gboolean version = FALSE;
static gboolean sign = FALSE;
static gboolean no_appstream = FALSE;
gchar **remaining_args = NULL;
gchar *updateinformation = NULL;
gchar *bintray_user = NULL;
gchar *bintray_repo = NULL;
gchar *sqfs_comp = "gzip";

// #####################################################################

static void die(const char *msg) {
    fprintf(stderr, "%s\n", msg);
    exit(1);
}

/* Function that prints the contents of a squashfs file
* using libsquashfuse (#include "squashfuse.h") */
int sfs_ls(char* image) {
    sqfs_err err = SQFS_OK;
    sqfs_traverse trv;
    sqfs fs;
    
    unsigned long fs_offset = get_elf_size(image);
    
    if ((err = sqfs_open_image(&fs, image, fs_offset)))
        die("sqfs_open_image error");
    
    if ((err = sqfs_traverse_open(&trv, &fs, sqfs_inode_root(&fs))))
        die("sqfs_traverse_open error");
    while (sqfs_traverse_next(&trv, &err)) {
        if (!trv.dir_end) {
            printf("%s\n", trv.path);
        }
    }
    if (err)
        die("sqfs_traverse_next error");
    sqfs_traverse_close(&trv);
    
    sqfs_fd_close(fs.fd);
    return 0;
}

/* Generate a squashfs filesystem using mksquashfs on the $PATH 
* execlp(), execvp(), and execvpe() search on the $PATH */
int sfs_mksquashfs(char *source, char *destination, int offset) {
    pid_t pid = fork();
    
    if (pid == -1) {
        // error, failed to fork()
        return(-1);
    } else if (pid > 0) {
        int status;
        waitpid(pid, &status, 0);
    } else {
        // we are the child
	gchar *offset_string;
	offset_string = g_strdup_printf("%i", offset);
        if(0==strcmp("xz", sqfs_comp))
        {
            // https://jonathancarter.org/2015/04/06/squashfs-performance-testing/ says:
            // improved performance by using a 16384 block size with a sacrifice of around 3% more squashfs image space
            execlp("mksquashfs", "mksquashfs", source, destination, "-offset", offset_string, "-comp", "xz", "-root-owned", "-noappend", "-Xdict-size", "100%", "-b", "16384", "-no-xattrs", "-root-owned", NULL);
        } else {
        execlp("mksquashfs", "mksquashfs", source, destination, "-offset", offset_string, "-comp", sqfs_comp, "-root-owned", "-noappend", "-no-xattrs", "-root-owned", NULL);
        }
        perror("execlp");   // execlp() returns only on error
        return(-1); // exec never returns
    }
    return(0);
}

/* Generate a squashfs filesystem
* The following would work if we link to mksquashfs.o after we renamed 
* main() to mksquashfs_main() in mksquashfs.c but we don't want to actually do
* this because squashfs-tools is not under a permissive license
* i *nt sfs_mksquashfs(char *source, char *destination) {
* char *child_argv[5];
* child_argv[0] = NULL;
* child_argv[1] = source;
* child_argv[2] = destination;
* child_argv[3] = "-root-owned";
* child_argv[4] = "-noappend";
* mksquashfs_main(5, child_argv);
* }
*/

gchar* find_first_matching_file(const gchar *real_path, const gchar *pattern) {
    GDir *dir;
    gchar *full_name;
    gchar *resulting;
    dir = g_dir_open(real_path, 0, NULL);
    if (dir != NULL) {
        const gchar *entry;
        while ((entry = g_dir_read_name(dir)) != NULL) {
            full_name = g_build_filename(real_path, entry, NULL);
            if (! g_file_test(full_name, G_FILE_TEST_IS_DIR)) {
                if(g_pattern_match_simple(pattern, entry))
                    return(full_name);
            }
            else {
                resulting = find_first_matching_file(full_name, pattern);
                if(resulting)
                    return(resulting);
            }
        }
        g_dir_close(dir);
    }
    else {
        g_warning("%s: %s", real_path, g_strerror(errno));
    }
    return NULL;
}

gchar* find_first_matching_file_nonrecursive(const gchar *real_path, const gchar *pattern) {
    GDir *dir;
    gchar *full_name;
    dir = g_dir_open(real_path, 0, NULL);
    if (dir != NULL) {
        const gchar *entry;
        while ((entry = g_dir_read_name(dir)) != NULL) {
            full_name = g_build_filename(real_path, entry, NULL);
            if (g_file_test(full_name, G_FILE_TEST_IS_REGULAR)) {
                if(g_pattern_match_simple(pattern, entry))
                    return(full_name);
            }
        }
        g_dir_close(dir);
    }
    else { 
        g_warning("%s: %s", real_path, g_strerror(errno));
    }
    return NULL;
}

gchar* get_desktop_entry(GKeyFile *kf, char *key) {
    gchar *value = g_key_file_get_string (kf, "Desktop Entry", key, NULL);
    if (! value){
        fprintf(stderr, "%s entry not found in desktop file\n", key);
    }
    return value;
}

/* in-place modification of the string, and assuming the buffer pointed to by
* line is large enough to hold the resulting string*/
static void replacestr(char *line, const char *search, const char *replace)
{
    char *sp = NULL;
    
    if ((sp = strstr(line, search)) == NULL) {
        return;
    }
    int search_len = strlen(search);
    int replace_len = strlen(replace);
    int tail_len = strlen(sp+search_len);
    
    memmove(sp+replace_len,sp+search_len,tail_len+1);
    memcpy(sp, replace, replace_len);
    
    /* Do it recursively again until no more work to do */
    
    if ((sp = strstr(line, search))) {
        replacestr(line, search, replace);
    }
}

// #####################################################################

static GOptionEntry entries[] =
{
    { "list", 'l', 0, G_OPTION_ARG_NONE, &list, "List files in SOURCE AppImage", NULL },
    { "updateinformation", 'u', 0, G_OPTION_ARG_STRING, &updateinformation, "Embed update information STRING; if zsyncmake is installed, generate zsync file", NULL },
    { "bintray-user", 0, 0, G_OPTION_ARG_STRING, &bintray_user, "Bintray user name", NULL },
    { "bintray-repo", 0, 0, G_OPTION_ARG_STRING, &bintray_repo, "Bintray repository", NULL },
    { "version", 0, 0, G_OPTION_ARG_NONE, &version, "Show version number", NULL },
    { "verbose", 'v', 0, G_OPTION_ARG_NONE, &verbose, "Produce verbose output", NULL },
    { "sign", 's', 0, G_OPTION_ARG_NONE, &sign, "Sign with gpg2", NULL },
    { "comp", 0, 0, G_OPTION_ARG_STRING, &sqfs_comp, "Squashfs compression", NULL },
    { "no-appstream", 'n', 0, G_OPTION_ARG_NONE, &no_appstream, "Do not check AppStream metadata", NULL },
    { G_OPTION_REMAINING, 0, 0, G_OPTION_ARG_FILENAME_ARRAY, &remaining_args, NULL, NULL },
    { 0,0,0,0,0,0,0 }
};

int
main (int argc, char *argv[])
{
    /* Parse VERSION environment variable.
     * We cannot use g_environ_getenv (g_get_environ() since it is too new for CentOS 6 */
    char* version_env;
    version_env = getenv("VERSION");

    /* Parse OWD environment variable.
     * If it is available then cd there. It is the original CWD prior to running AppRun */
    char* owd_env = NULL;
    owd_env = getenv("OWD");    
    if(NULL!=owd_env){
        int ret;
        ret = chdir(owd_env);
        if (ret != 0){
            fprintf(stderr, "Could not cd into %s\n", owd_env);
            exit(1);
            
        }
    }
        
    GError *error = NULL;
    GOptionContext *context;
    char command[PATH_MAX];
    
    context = g_option_context_new ("SOURCE [DESTINATION] - Generate, extract, and inspect AppImages");
    g_option_context_add_main_entries (context, entries, NULL);
    // g_option_context_add_group (context, gtk_get_option_group (TRUE));
    if (!g_option_context_parse (context, &argc, &argv, &error))
    {
        fprintf(stderr, "Option parsing failed: %s\n", error->message);
        exit(1);
    }

    if(version){
        fprintf(stderr,"Version: %s\n", VERSION_NUMBER);
        exit(0);
    }

    if(!((0 == strcmp(sqfs_comp, "gzip")) || (0 ==strcmp(sqfs_comp, "xz"))))
        die("Only gzip (faster execution, larger files) and xz (slower execution, smaller files) compression is supported at the moment. Let us know if there are reasons for more, should be easy to add. You could help the project by doing some systematic size/performance measurements. Watch for size, execution speed, and zsync delta size.");
    /* Check for dependencies here. Better fail early if they are not present. */
    if(! g_find_program_in_path ("mksquashfs"))
        die("mksquashfs is missing but required, please install it");
    if(! g_find_program_in_path ("zsyncmake"))
        g_print("WARNING: zsyncmake is missing, please install it if you want to use binary delta updates\n");
    if(! no_appstream)
        if(! g_find_program_in_path ("appstreamcli"))
            g_print("WARNING: appstreamcli is missing, please install it if you want to use AppStream metadata\n");
    if(! g_find_program_in_path ("gpg2"))
        g_print("WARNING: gpg2 is missing, please install it if you want to create digital signatures\n");
    if(! g_find_program_in_path ("sha256sum"))
        g_print("WARNING: sha256sum is missing, please install it if you want to create digital signatures\n");
    
    if(!&remaining_args[0])
        die("SOURCE is missing");
    
    /* If in list mode */
    if (list){
        sfs_ls(remaining_args[0]);
        exit(0);
    }
    
    /* If the first argument is a directory, then we assume that we should package it */
    if (g_file_test (remaining_args[0], G_FILE_TEST_IS_DIR)){
        char *destination;
        char source[PATH_MAX];
        realpath(remaining_args[0], source);
        
        /* Check if *.desktop file is present in source AppDir */
        gchar *desktop_file = find_first_matching_file_nonrecursive(source, "*.desktop");
        if(desktop_file == NULL){
            die("$ID.desktop file not found");
        }
        if(verbose)
            fprintf (stdout, "Desktop file: %s\n", desktop_file);
        
        /* Read information from .desktop file */
        GKeyFile *kf = g_key_file_new ();
        if (!g_key_file_load_from_file (kf, desktop_file, 0, NULL))
            die(".desktop file cannot be parsed");
        
        if(verbose){
            fprintf (stderr,"Name: %s\n", get_desktop_entry(kf, "Name"));
            fprintf (stderr,"Icon: %s\n", get_desktop_entry(kf, "Icon"));
            fprintf (stderr,"Exec: %s\n", get_desktop_entry(kf, "Exec"));
            fprintf (stderr,"Comment: %s\n", get_desktop_entry(kf, "Comment"));
            fprintf (stderr,"Type: %s\n", get_desktop_entry(kf, "Type"));
            fprintf (stderr,"Categories: %s\n", get_desktop_entry(kf, "Categories"));
        }
        
        /* Determine the architecture */
        gchar *arch = getenv("ARCH");
        FILE *fp;
        /* If no $ARCH variable is set check a file */
        if (!arch) {
            gchar *archfile = NULL;
            /* We use the next best .so that we can find to determine the architecture */
            archfile = find_first_matching_file(source, "*.so.*");
            if(!archfile)
            {
                /* If we found no .so we try to guess the main executable - this might be a script though */
                // char guessed_bin_path[PATH_MAX];
                // sprintf (guessed_bin_path, "%s/usr/bin/%s", source,  g_strsplit_set(get_desktop_entry(kf, "Exec"), " ", -1)[0]);
                // archfile = guessed_bin_path;
                archfile = "/proc/self/exe";
            }
            if(verbose)
                fprintf (stderr,"File used for determining architecture: %s\n", archfile);
            
            char line[PATH_MAX];
            char command[PATH_MAX];
            sprintf (command, "/usr/bin/file -L -N -b %s", archfile);
            fp = popen(command, "r");
            if (fp == NULL)
                die("Failed to run file command");
            fgets(line, sizeof(line)-1, fp);
            arch = g_strstrip(g_strsplit_set(line, ",", -1)[1]);
            replacestr(arch, "-", "_");
            fprintf (stderr,"Arch: %s\n", arch+1);
            pclose(fp);

            if(!arch)
            {
                printf("The architecture could not be determined, assuming 'all'\n");
                arch="all";
            }
        }
        
        char app_name_for_filename[PATH_MAX];
        sprintf(app_name_for_filename, "%s", get_desktop_entry(kf, "Name"));
        replacestr(app_name_for_filename, " ", "_");
        
        if(verbose)
            fprintf (stderr,"App name for filename: %s\n", app_name_for_filename);
        
        if (remaining_args[1]) {
            destination = remaining_args[1];
        } else {
            /* No destination has been specified, to let's construct one
            * TODO: Find out the architecture and use a $VERSION that might be around in the env */
            char dest_path[PATH_MAX];
            sprintf (dest_path, "%s-%s.AppImage", app_name_for_filename, arch);
            
            if(verbose)
                fprintf (stderr,"dest_path: %s\n", dest_path);
            
            if (version_env!=NULL)
                sprintf (dest_path, "%s-%s-%s.AppImage", app_name_for_filename, version_env, arch);
            
            destination = dest_path;
            replacestr(destination, " ", "_");
            
            // destination = basename(br_strcat(source, ".AppImage"));
            fprintf (stdout, "DESTINATION not specified, so assuming %s\n", destination);
        }
        fprintf (stdout, "%s should be packaged as %s\n", source, destination);
        /* Check if the Icon file is how it is expected */
        gchar* icon_name = get_desktop_entry(kf, "Icon");
        gchar* icon_file_path = NULL;
        gchar* icon_file_png;
        gchar* icon_file_svg;
        gchar* icon_file_svgz;
        gchar* icon_file_xpm;
        icon_file_png = g_strdup_printf("%s/%s.png", source, icon_name);
        icon_file_svg = g_strdup_printf("%s/%s.svg", source, icon_name);
        icon_file_svgz = g_strdup_printf("%s/%s.svgz", source, icon_name);
        icon_file_xpm = g_strdup_printf("%s/%s.xpm", source, icon_name);
        if (g_file_test(icon_file_png, G_FILE_TEST_IS_REGULAR)) {
            icon_file_path = icon_file_png;
        } else if(g_file_test(icon_file_svg, G_FILE_TEST_IS_REGULAR)) {
            icon_file_path = icon_file_svg;
        } else if(g_file_test(icon_file_svgz, G_FILE_TEST_IS_REGULAR)) {
            icon_file_path = icon_file_svgz;
        } else if(g_file_test(icon_file_xpm, G_FILE_TEST_IS_REGULAR)) {
            icon_file_path = icon_file_xpm;
        } else {
            fprintf (stderr, "%s{.png,.svg,.svgz,.xpm} not present but defined in desktop file\n", icon_name);
            exit(1);
        }
       
        /* Check if .DirIcon is present in source AppDir */
        gchar *diricon_path = g_build_filename(source, ".DirIcon", NULL);
        
        if (! g_file_test(diricon_path, G_FILE_TEST_EXISTS)){
            fprintf (stderr, "Deleting pre-existing .DirIcon\n");
            g_unlink(diricon_path);
        }
        if (! g_file_test(diricon_path, G_FILE_TEST_IS_REGULAR)){
            fprintf (stderr, "Creating .DirIcon symlink based on information from desktop file\n");
            int res = symlink(basename(icon_file_path), diricon_path);
            if(res)
                die("Could not symlink .DirIcon");
        }
        
        /* Check if AppStream upstream metadata is present in source AppDir */
        if(! no_appstream){
            char application_id[PATH_MAX];
            sprintf (application_id,  "%s", basename(desktop_file));
            replacestr(application_id, ".desktop", ".appdata.xml");
            gchar *appdata_path = g_build_filename(source, "/usr/share/metainfo/", application_id, NULL);
            if (! g_file_test(appdata_path, G_FILE_TEST_IS_REGULAR)){
                fprintf (stderr, "WARNING: AppStream upstream metadata is missing, please consider creating it\n");
                fprintf (stderr, "         in usr/share/metainfo/%s\n", application_id);
                fprintf (stderr, "         Please see https://www.freedesktop.org/software/appstream/docs/chap-Quickstart.html#sect-Quickstart-DesktopApps\n");
                fprintf (stderr, "         for more information.\n");
                /* As a courtesy, generate one to be filled by the user */
                if(g_find_program_in_path ("appstream-util")) {
                    gchar *appdata_dir = g_build_filename(source, "/usr/share/metainfo/", NULL);
                    g_mkdir_with_parents(appdata_dir, 0755);
                    sprintf (command, "%s appdata-from-desktop %s %s", g_find_program_in_path ("appstream-util"), desktop_file, appdata_path);
                    int ret = system(command);
                    if (ret != 0)
                        die("Failed to generate AppStream template");
                    fprintf (stderr, "AppStream template has been generated in in %s, please edit it\n", appdata_path);
                    exit(1);
                }
            } else {
                fprintf (stderr, "AppStream upstream metadata found in usr/share/metainfo/%s\n", application_id);
                /* Use ximion's appstreamcli to make sure that desktop file and appdata match together */
                if(g_find_program_in_path ("appstreamcli")) {
                    sprintf (command, "%s validate-tree %s", g_find_program_in_path ("appstreamcli"), source);
                    int ret = system(command);
                    if (ret != 0)
                        die("Failed to validate AppStream information with appstreamcli");
                }
                /* It seems that hughsie's appstream-util does additional validations */
                if(g_find_program_in_path ("appstream-util")) {
                    sprintf (command, "%s validate-relax %s", g_find_program_in_path ("appstream-util"), appdata_path);
                    int ret = system(command);
                    if (ret != 0)
                        die("Failed to validate AppStream information with appstream-util");
                }
            }
        }
        
        /* Upstream mksquashfs can currently not start writing at an offset,
        * so we need a patched one. https://github.com/plougher/squashfs-tools/pull/13
        * should hopefully change that. */

        fprintf (stderr, "Generating squashfs...\n");
        /* runtime is embedded into this executable
        * http://stupefydeveloper.blogspot.de/2008/08/cc-embed-binary-data-into-elf.html */
        int size = (int)((void *)&_binary_runtime_end - (void *)&_binary_runtime_start);
        char *data = (char *)&_binary_runtime_start;
        if (verbose)
            printf("Size of the embedded runtime: %d bytes\n", size);
        
        int result = sfs_mksquashfs(source, destination, size);
        if(result != 0)
            die("sfs_mksquashfs error");
        
        fprintf (stderr, "Embedding ELF...\n");
        FILE *fpdst = fopen(destination, "rb+");
        if (fpdst == NULL) {
            die("Not able to open the AppImage for writing, aborting");
        }

        fseek(fpdst, 0, SEEK_SET);
        fwrite(data, size, 1, fpdst);
        fclose(fpdst);

        fprintf (stderr, "Marking the AppImage as executable...\n");
        if (chmod (destination, 0755) < 0) {
            printf("Could not set executable bit, aborting\n");
            exit(1);
        }
        
        if(bintray_user != NULL){
            if(bintray_repo != NULL){
                char buf[1024];
                sprintf(buf, "bintray-zsync|%s|%s|%s|%s-_latestVersion-%s.AppImage.zsync", bintray_user, bintray_repo, app_name_for_filename, app_name_for_filename, arch);
                updateinformation = buf;
                printf("%s\n", updateinformation);
            }
        }
        
        /* If updateinformation was provided, then we check and embed it */
        if(updateinformation != NULL){
            if(!g_str_has_prefix(updateinformation,"zsync|"))
                if(!g_str_has_prefix(updateinformation,"bintray-zsync|"))
                    die("The provided updateinformation is not in a recognized format");
                
            gchar **ui_type = g_strsplit_set(updateinformation, "|", -1);
                        
            if(verbose)
                printf("updateinformation type: %s\n", ui_type[0]);
            /* TODO: Further checking of the updateinformation */
            
          
            unsigned long ui_offset = 0;
            unsigned long ui_length = 0;
            get_elf_section_offset_and_lenghth(destination, ".upd_info", &ui_offset, &ui_length);
            if(verbose) {
                printf("ui_offset: %lu\n", ui_offset);
                printf("ui_length: %lu\n", ui_length);
            }
            if(ui_offset == 0) {
                die("Could not determine offset for updateinformation");
            } else {
                if(strlen(updateinformation)>ui_length)
                    die("updateinformation does not fit into segment, aborting");
                FILE *fpdst2 = fopen(destination, "r+");
                if (fpdst2 == NULL)
                    die("Not able to open the destination file for writing, aborting");
                fseek(fpdst2, ui_offset, SEEK_SET);
                // fseek(fpdst2, ui_offset, SEEK_SET);
                // fwrite(0x00, 1, 1024, fpdst); // FIXME: Segfaults; why?
                // fseek(fpdst, ui_offset, SEEK_SET);
                fwrite(updateinformation, strlen(updateinformation), 1, fpdst2);
                fclose(fpdst2);
            }
        }

        if(sign){
            /* The user has indicated that he wants to sign */
            gchar *gpg2_path = g_find_program_in_path ("gpg2");
            gchar *sha256sum_path = g_find_program_in_path ("sha256sum");
            if(!gpg2_path){
                fprintf (stderr, "gpg2 is not installed, cannot sign\n");
            }
            else if(!sha256sum_path){
                fprintf (stderr, "sha256sum is not installed, cannot sign\n");
            } else {
                fprintf (stderr, "gpg2 and sha256sum are installed and user requested to sign, "
                "hence signing\n");
                char *digestfile;
                digestfile = br_strcat(destination, ".digest");
                char *ascfile;
                ascfile = br_strcat(destination, ".digest.asc");
                if (g_file_test (digestfile, G_FILE_TEST_IS_REGULAR))
                    unlink(digestfile);
                sprintf (command, "%s %s", sha256sum_path, destination);
                if(verbose)
                    fprintf (stderr, "%s\n", command);
                fp = popen(command, "r");
                if (fp == NULL)
                    die("sha256sum command did not succeed");
                char output[1024];
                fgets(output, sizeof(output)-1, fp);
                if(verbose)
                    printf("sha256sum: %s\n", g_strsplit_set(output, " ", -1)[0]);
                FILE *fpx = fopen(digestfile, "w");
                if (fpx != NULL)
                {
                    fputs(g_strsplit_set(output, " ", -1)[0], fpx);
                    fclose(fpx);
                }
                if(WEXITSTATUS(pclose(fp)) != 0)
                    die("sha256sum command did not succeed");
                if (g_file_test (ascfile, G_FILE_TEST_IS_REGULAR))
                    unlink(ascfile);
                sprintf (command, "%s --detach-sign --armor %s", gpg2_path, digestfile);
                if(verbose)
                    fprintf (stderr, "%s\n", command);
                fp = popen(command, "r");
                if(WEXITSTATUS(pclose(fp)) != 0) { 
                    fprintf (stderr, "ERROR: gpg2 command did not succeed, could not sign, continuing\n");
                } else {
                    unsigned long sig_offset = 0;
                    unsigned long sig_length = 0;
                    get_elf_section_offset_and_lenghth(destination, ".sha256_sig", &sig_offset, &sig_length);
                    if(verbose) {
                        printf("sig_offset: %lu\n", sig_offset);
                        printf("sig_length: %lu\n", sig_length);
                    }
                    if(sig_offset == 0) {
                        die("Could not determine offset for signature");
                    } else {
                        FILE *fpdst3 = fopen(destination, "r+");
                        if (fpdst3 == NULL)
                            die("Not able to open the destination file for writing, aborting");
    //                    if(strlen(updateinformation)>sig_length)
    //                        die("signature does not fit into segment, aborting");
                        fseek(fpdst3, sig_offset, SEEK_SET);
                        FILE *fpsrc2 = fopen(ascfile, "rb");
                        if (fpsrc2 == NULL) {
                            die("Not able to open the asc file for reading, aborting");
                        }
                        char byte;
                        while (!feof(fpsrc2))
                        {
                            fread(&byte, sizeof(char), 1, fpsrc2);
                            fwrite(&byte, sizeof(char), 1, fpdst3);
                        }
                        fclose(fpsrc2);
                        fclose(fpdst3);
                    }
                    if (g_file_test (ascfile, G_FILE_TEST_IS_REGULAR))
                        unlink(ascfile);
                    if (g_file_test (digestfile, G_FILE_TEST_IS_REGULAR))
                        unlink(digestfile);
                }
            }
        }
        
        /* If updateinformation was provided, then we also generate the zsync file (after having signed the AppImage) */
        if(updateinformation != NULL){
            gchar *zsyncmake_path = g_find_program_in_path ("zsyncmake");
            if(!zsyncmake_path){
                fprintf (stderr, "zsyncmake is not installed, skipping\n");
            } else {
                fprintf (stderr, "zsyncmake is installed and updateinformation is provided, "
                "hence generating zsync file\n");
                sprintf (command, "%s %s -u %s", zsyncmake_path, destination, basename(destination));
                if(verbose)
                    fprintf (stderr, "%s\n", command);
                fp = popen(command, "r");
                if (fp == NULL)
                    die("Failed to run zsyncmake command");            
            }
         } 
         
        fprintf (stderr, "Success\n");
        }
    
    /* If the first argument is a regular file, then we assume that we should unpack it */
    if (g_file_test (remaining_args[0], G_FILE_TEST_IS_REGULAR)){
        fprintf (stdout, "%s is a file, assuming it is an AppImage and should be unpacked\n", remaining_args[0]);
        die("To be implemented");
    }
    
    return 0;    
}