Build patched libfuse3 to find more fusermount binaries (#11)

Author: probonopd

build.sh

@@ -8,13 +8,26 @@ if ! command -v apk; then
 fi
 
 apk update
-apk add alpine-sdk util-linux strace file autoconf automake libtool
+apk add alpine-sdk util-linux strace file autoconf automake libtool xz
+
+# Build static libfuse3 with patch for https://github.com/AppImage/type2-runtime/issues/10
+apk add eudev-dev gettext-dev linux-headers meson # From https://git.alpinelinux.org/aports/tree/main/fuse3/APKBUILD
+wget -c -q "https://github.com/libfuse/libfuse/releases/download/fuse-3.15.0/fuse-3.15.0.tar.xz"
+tar xf fuse-3.*.tar.xz
+cd fuse-3.*/
+patch -p1 < ../patches/libfuse/mount.c.diff
+mkdir build
+cd build
+meson setup --prefix=/usr ..
+meson configure --default-library static
+ninja install
+cd ../../
 
 # Minimize binary size
 export CFLAGS="-ffunction-sections -fdata-sections -Os"
 
 # Build static squashfuse
-apk add fuse3-dev fuse3-static zstd-dev zlib-dev zlib-static # fuse-static fuse-dev
+apk add zstd-dev zlib-dev zlib-static # fuse3-dev fuse3-static fuse-static fuse-dev
 find / -name "libzstd.*" 2>/dev/null || true
 wget -c -q "https://github.com/vasi/squashfuse/archive/e51978c.tar.gz"
 tar xf e51978c.tar.gz

chroot_build.sh

@@ -18,6 +18,7 @@ cd -
 #############################################
 
 sudo cp -r ./src miniroot/src
+sudo cp -r ./patches miniroot/patches
 
 sudo mount -o bind /dev miniroot/dev
 sudo mount -t proc none miniroot/proc

patches/libfuse/mount.c.diff

@@ -0,0 +1,130 @@
+diff --git a/lib/mount.c b/lib/mount.c
+index d71e6fc55..acc1711ff 100644
+--- a/lib/mount.c
++++ b/lib/mount.c
+@@ -41,7 +41,6 @@
+ #define umount2(mnt, flags) unmount(mnt, (flags == 2) ? MNT_FORCE : 0)
+ #endif
+ 
+-#define FUSERMOUNT_PROG		"fusermount3"
+ #define FUSE_COMMFD_ENV		"_FUSE_COMMFD"
+ 
+ #ifndef HAVE_FORK
+@@ -117,17 +116,79 @@ 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)
++{
++	// 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;
++	}
++
++	// Check if there is a binary "fusermount3"
++	prog = findBinaryInFusermountDir("fusermount3");
++	if (access(prog, X_OK) == 0)
++		return prog;
++
++	// 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;
++
++	// 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 all else fails, return NULL
++	return NULL;
++}
++
+ 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);
++	}
+ }
+ 
+ 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 };
+ 		exec_fusermount(argv);
+ 		_exit(1);
+ 	} else if (pid != -1)
+@@ -300,7 +361,7 @@ 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",
+ 				       "--", mountpoint, NULL };
+ 
+ 		exec_fusermount(argv);
+@@ -346,7 +407,7 @@ static int setup_auto_unmount(const char *mountpoint, int quiet)
+ 			}
+ 		}
+ 
+-		argv[a++] = FUSERMOUNT_PROG;
++		argv[a++] = fuse_mount_prog();
+ 		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,
+ 			}
+ 		}
+ 
+-		argv[a++] = FUSERMOUNT_PROG;
++		argv[a++] = fuse_mount_prog();
+ 		if (opts) {
+ 			argv[a++] = "-o";
+ 			argv[a++] = opts;
+@@ -421,7 +482,7 @@ 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");
+ 		_exit(1);
+ 	}