Find usermountN and set FUSERMOUNT_PROG if not set

patches/libfuse/mount.c.diff

@@ -1,5 +1,5 @@
 diff --git a/lib/mount.c b/lib/mount.c
-index d71e6fc55..acc1711ff 100644
+index d71e6fc..ab3f54b 100644
 --- a/lib/mount.c
 +++ b/lib/mount.c
 @@ -41,7 +41,6 @@
@@ -10,121 +10,96 @@ index d71e6fc55..acc1711ff 100644
  #define FUSE_COMMFD_ENV		"_FUSE_COMMFD"
 
  #ifndef HAVE_FORK
-@@ -117,17 +116,79 @@ static const struct fuse_opt fuse_mount_opts[] = {
+@@ -117,17 +116,44 @@ static const struct fuse_opt fuse_mount_opts[] = {
  	FUSE_OPT_END
  };
 
-+int fileExists(const char* path);
-+char* findBinaryInFusermountDir(const char* binaryName);
-+
-+int fileExists(const char* path) {
-+    FILE* file = fopen(path, "r");
-+    if (file) {
-+        fclose(file);
-+        return 1;
-+    }
-+    return 0;
-+}
-+
-+char* findBinaryInFusermountDir(const char* binaryName) {
-+    // For security reasons, we do not search the binary on the $PATH;
-+	// instead, we check if the binary exists in FUSERMOUNT_DIR
-+	// as defined in meson.build
-+	char* binaryPath = malloc(strlen(FUSERMOUNT_DIR) + strlen(binaryName) + 2);
-+	strcpy(binaryPath, FUSERMOUNT_DIR);
-+	strcat(binaryPath, "/");
-+	strcat(binaryPath, binaryName);
-+	if (fileExists(binaryPath)) {
-+		return binaryPath;
-+	}
-+
-+	// If the binary does not exist in FUSERMOUNT_DIR, return NULL
-+	return NULL;
-+}
-+
-+static const char *fuse_mount_prog(void)
++/**
++ * Returns FUSERMOUNT_PROG path from environment variable.
++ *
++ * If $FUSERMOUNT_PROG is not set, the program exits.
++ * 
++ * Call with FUSERMOUNT_PROG_DEBUG=nonzerovalue to make the code print the value before evaluation.
++ */
++static const char *fusermountProg(void)
 +{
-+	// Check if the FUSERMOUNT_PROG environment variable is set and if so, use it
-+	const char *prog = getenv("FUSERMOUNT_PROG");
-+	if (prog) {
-+		if (access(prog, X_OK) == 0)
-+			return prog;
-+	}
++	static const char envVar[] = "FUSERMOUNT_PROG";
++	char *fusermountProg = getenv(envVar);
 +
-+	// Check if there is a binary "fusermount3"
-+	prog = findBinaryInFusermountDir("fusermount3");
-+	if (access(prog, X_OK) == 0)
-+		return prog;
++	static const char debugEnvVarSuffix[] = "_DEBUG";
++	char debugEnvVar[sizeof(envVar) + sizeof(debugEnvVarSuffix) + 1];
++	sprintf(debugEnvVar, "%s%s", envVar, debugEnvVarSuffix);
 +
-+	// Check if there is a binary called "fusermount"
-+	// This is known to work for our purposes
-+	prog = findBinaryInFusermountDir("fusermount");
-+	if (access(prog, X_OK) == 0)
-+		return prog;
++	if (fusermountProg == NULL) {
++		fprintf(stderr, "Error: $%s not set\n", envVar);
++		exit(1);
++	}
 +
-+	// For i = 4...99, check if there is a binary called "fusermount" + i
-+	// It is not yet known whether this will work for our purposes, but it is better than not even attempting
-+	for (int i = 4; i < 100; i++) {
-+		prog = findBinaryInFusermountDir("fusermount" + i);
-+		if (access(prog, X_OK) == 0)
-+			return prog;
++	if (getenv(debugEnvVar) != NULL) {
++		fprintf(stderr, "$%s: %s\n", envVar, fusermountProg);
 +	}
 +
-+	// If all else fails, return NULL
-+	return NULL;
++	return fusermountProg;
 +}
 +
  static void exec_fusermount(const char *argv[])
  {
 -	execv(FUSERMOUNT_DIR "/" FUSERMOUNT_PROG, (char **) argv);
 -	execvp(FUSERMOUNT_PROG, (char **) argv);
-+	const char *fusermount_prog = fuse_mount_prog();
-+	if (fusermount_prog) {
-+		execv(fusermount_prog, (char **) argv);
-+	}
++	execv(fusermountProg(), (char **) argv);
  }
 
  void fuse_mount_version(void)
  {
  	int pid = fork();
  	if (!pid) {
 -		const char *argv[] = { FUSERMOUNT_PROG, "--version", NULL };
-+		const char *argv[] = { fuse_mount_prog(), "--version", NULL };
++		const char *argv[] = { fusermountProg(), "--version", NULL };
  		exec_fusermount(argv);
  		_exit(1);
  	} else if (pid != -1)
-@@ -300,7 +361,7 @@ void fuse_kern_unmount(const char *mountpoint, int fd)
+@@ -300,7 +326,7 @@ void fuse_kern_unmount(const char *mountpoint, int fd)
  		return;
 
  	if(pid == 0) {
 -		const char *argv[] = { FUSERMOUNT_PROG, "-u", "-q", "-z",
-+		const char *argv[] = { fuse_mount_prog(), "-u", "-q", "-z",
++		const char *argv[] = { fusermountProg(), "-u", "-q", "-z",
  				       "--", mountpoint, NULL };
 
  		exec_fusermount(argv);
-@@ -346,7 +407,7 @@ static int setup_auto_unmount(const char *mountpoint, int quiet)
+@@ -346,7 +372,7 @@ static int setup_auto_unmount(const char *mountpoint, int quiet)
  			}
  		}
 
 -		argv[a++] = FUSERMOUNT_PROG;
-+		argv[a++] = fuse_mount_prog();
++		argv[a++] = fusermountProg();
  		argv[a++] = "--auto-unmount";
  		argv[a++] = "--";
  		argv[a++] = mountpoint;
-@@ -407,7 +468,7 @@ static int fuse_mount_fusermount(const char *mountpoint, struct mount_opts *mo,
+@@ -357,7 +383,7 @@ static int setup_auto_unmount(const char *mountpoint, int quiet)
+ 		snprintf(env, sizeof(env), "%i", fds[0]);
+ 		setenv(FUSE_COMMFD_ENV, env, 1);
+ 		exec_fusermount(argv);
+-		perror("fuse: failed to exec fusermount3");
++		perror("fuse: failed to exec $FUSERMOUNT_PROG");
+ 		_exit(1);
+ 	}
+
+@@ -407,7 +433,7 @@ static int fuse_mount_fusermount(const char *mountpoint, struct mount_opts *mo,
  			}
  		}
 
 -		argv[a++] = FUSERMOUNT_PROG;
-+		argv[a++] = fuse_mount_prog();
++		argv[a++] = fusermountProg();
  		if (opts) {
  			argv[a++] = "-o";
  			argv[a++] = opts;
-@@ -421,7 +482,7 @@ static int fuse_mount_fusermount(const char *mountpoint, struct mount_opts *mo,
+@@ -421,7 +447,7 @@ static int fuse_mount_fusermount(const char *mountpoint, struct mount_opts *mo,
  		snprintf(env, sizeof(env), "%i", fds[0]);
  		setenv(FUSE_COMMFD_ENV, env, 1);
  		exec_fusermount(argv);
 -		perror("fuse: failed to exec fusermount3");
-+		perror("fuse: failed to exec fusermount");
++		perror("fuse: failed to exec $FUSERMOUNT_PROG");
  		_exit(1);
  	}
+

src/runtime/runtime.c

@@ -5,7 +5,7 @@
  * as possible (one .c file) and use as few external dependencies
  * as possible
  *
- * Copyright (c) 2004-22 Simon Peter
+ * Copyright (c) 2004-24 Simon Peter
  * Portions Copyright (c) 2007 Alexander Larsson
  * Portions from WjCryptLib_Md5 originally written by Alexander Peslyak,
    modified by WaterJuice retaining Public Domain license
@@ -62,6 +62,10 @@ extern int sqfs_opt_proc(void* data, const char* arg, int key, struct fuse_args*
 #include <sys/mman.h>
 #include <stdint.h>
 #include <libgen.h>
+#include <dirent.h>
+#include <ctype.h>
+
+const char* fusermountPath = NULL;
 
 typedef struct {
     uint32_t lo;
@@ -405,6 +409,99 @@ int appimage_print_binary(char* fname, unsigned long offset, unsigned long lengt
 	return 0;
 }
 
+char* find_fusermount(bool verbose) {
+    char* fusermount_base = "fusermount";
+
+    char* fusermount_path = getenv("PATH");
+    if (fusermount_path == NULL) {
+        return NULL;
+    }
+
+    char* path_copy = strdup(fusermount_path);
+    char* dir = strtok(path_copy, ":");
+
+    while (dir != NULL) {
+        DIR* dir_ptr = opendir(dir);
+        if (dir_ptr == NULL) {
+            dir = strtok(NULL, ":");
+            continue;
+        }
+
+        struct dirent* entry;
+        while ((entry = readdir(dir_ptr)) != NULL) {
+            // Check if the entry starts with "fusermount"
+            if (strncmp(entry->d_name, fusermount_base, 10) == 0) {
+                // Check if the rest of the entry is a digit
+                char* suffix = entry->d_name + 10;
+                int j = 0;
+                while (suffix[j] != '\0' && isdigit(suffix[j])) {
+                    j++;
+                }
+
+                if (suffix[j] == '\0') {
+                    // Construct the full path of the entry
+                    char* fusermount_full_path = malloc(strlen(dir) + strlen(entry->d_name) + 2);
+                    sprintf(fusermount_full_path, "%s/%s", dir, entry->d_name);
+
+                    // Check if the binary is setuid root
+                    struct stat sb;
+                    if (stat(fusermount_full_path, &sb) == -1) {
+                        perror("stat");
+                        free(fusermount_full_path);
+                        continue;
+                    }
+
+                    if (sb.st_uid != 0 || (sb.st_mode & S_ISUID) == 0) {
+                        if (verbose) {
+                            printf("Not setuid root, skipping...\n");
+                        }
+                        free(fusermount_full_path);
+                        continue;
+                    }
+
+                    if (verbose) {
+                        printf("Found setuid root executable: %s\n", fusermount_full_path);
+                    }
+
+                    pid_t pid = fork();
+                    if (pid == -1) {
+                        perror("fork");
+                        free(fusermount_full_path);
+                        continue;
+                    }
+
+                    if (pid == 0) {
+                        // Child process
+                        char* args[] = {fusermount_full_path, "--version", NULL};
+                        execvp(fusermount_full_path, args);
+                        // If execvp returns, it means the executable was not found
+                        exit(1);
+                    } else {
+                        // Parent process
+                        int status;
+                        waitpid(pid, &status, 0);
+
+                        if (WIFEXITED(status) && WEXITSTATUS(status) == 0) {
+                            // The executable was found and executed successfully
+                            closedir(dir_ptr);
+                            free(path_copy);
+                            return fusermount_full_path;
+                        }
+
+                        free(fusermount_full_path);
+                    }
+                }
+            }
+        }
+
+        closedir(dir_ptr);
+        dir = strtok(NULL, ":");
+    }
+
+    free(path_copy);
+    return NULL;
+}
+
 /* Exit status to use when launching an AppImage fails.
  * For applications that assign meanings to exit status codes (e.g. rsync),
  * we avoid "cluttering" pre-defined exit status codes by using 127 which
@@ -1330,6 +1427,11 @@ char* appimage_hexlify(const char* bytes, const size_t numBytes) {
 }
 
 int main(int argc, char* argv[]) {
+    const bool verbose = (getenv("VERBOSE") != NULL);
+    if (verbose) {
+        fprintf(stderr, "Running in verbose mode\n");
+    }
+
     char appimage_path[PATH_MAX];
     char argv0_path[PATH_MAX];
     char* arg;
@@ -1410,8 +1512,6 @@ int main(int argc, char* argv[]) {
             exit(1);
         }
 
-        const bool verbose = (getenv("VERBOSE") != NULL);
-
         if (!extract_appimage(appimage_path, "squashfs-root/", pattern, true, verbose)) {
             exit(1);
         }
@@ -1473,8 +1573,6 @@ int main(int argc, char* argv[]) {
         strcat(prefix, hexlified_digest);
         free(hexlified_digest);
 
-        const bool verbose = (getenv("VERBOSE") != NULL);
-
         if (!extract_appimage(appimage_path, prefix, NULL, false, verbose)) {
             fprintf(stderr, "Failed to extract AppImage\n");
             exit(EXIT_EXECERROR);
@@ -1556,7 +1654,7 @@ int main(int argc, char* argv[]) {
         appimage_print_binary(appimage_path, offset, length);
         exit(0);
     }
-    
+
     portable_option(arg, appimage_path, "home");
     portable_option(arg, appimage_path, "config");
 
@@ -1600,6 +1698,20 @@ int main(int argc, char* argv[]) {
     if (pid == 0) {
         /* in child */
 
+        fusermountPath = getenv("FUSERMOUNT_PROG");
+        if (fusermountPath == NULL) {
+            char* new_prog = find_fusermount(verbose);
+            if (new_prog != NULL) {
+                setenv("FUSERMOUNT_PROG", new_prog, 1);
+                if (verbose) {
+                    fprintf(stderr, "FUSERMOUNT_PROG set to %s\n", new_prog);
+                }
+                free(new_prog);
+            } else {
+                printf("Error: No suitable fusermount binary found on the $PATH\n");
+            }
+        }
+
         char* child_argv[5];
 
         /* close read pipe */