From 056d8ddda8d5236ac94d6897b674291679c05e91 Mon Sep 17 00:00:00 2001 From: Matthias Schiffer Date: Sun, 23 Apr 2017 02:28:13 +0200 Subject: [PATCH] upgraded: link dynamically, chroot during exec The chroot ensures we don't reference anything on the rootfs and is reverted after the upgraded exec. While we're at it, also improve error handling a bit. This change also required changes to sysupgrade, as the dynamically linked version is expected at a different location, and libraries need to be made available. Signed-off-by: Matthias Schiffer --- system.c | 25 +++++++++++++++++++------ upgraded/CMakeLists.txt | 10 +--------- upgraded/upgraded.c | 26 +++++++++++++++++++++----- watchdog.c | 9 +++++++-- watchdog.h | 4 ++-- 5 files changed, 50 insertions(+), 24 deletions(-) diff --git a/system.c b/system.c index bb2abe5..193c9b0 100644 --- a/system.c +++ b/system.c @@ -345,27 +345,40 @@ static int proc_signal(struct ubus_context *ctx, struct ubus_object *obj, enum { SYSUPGRADE_PATH, + SYSUPGRADE_PREFIX, __SYSUPGRADE_MAX }; static const struct blobmsg_policy sysupgrade_policy[__SYSUPGRADE_MAX] = { [SYSUPGRADE_PATH] = { .name = "path", .type = BLOBMSG_TYPE_STRING }, + [SYSUPGRADE_PREFIX] = { .name = "prefix", .type = BLOBMSG_TYPE_STRING }, }; static void -procd_spawn_upgraded(char *path) +procd_exec_upgraded(const char *prefix, char *path) { char *wdt_fd = watchdog_fd(); - char *argv[] = { "/tmp/upgraded", NULL, NULL}; + char *argv[] = { "/sbin/upgraded", NULL, NULL}; + + if (chroot(prefix)) { + fprintf(stderr, "Failed to chroot for upgraded exec.\n"); + return; + } argv[1] = path; DEBUG(2, "Exec to upgraded now\n"); if (wdt_fd) { - watchdog_no_cloexec(); + watchdog_set_cloexec(false); setenv("WDTFD", wdt_fd, 1); } execvp(argv[0], argv); + + /* Cleanup on failure */ + fprintf(stderr, "Failed to exec upgraded.\n"); + unsetenv("WDTFD"); + watchdog_set_cloexec(true); + chroot("."); } static int sysupgrade(struct ubus_context *ctx, struct ubus_object *obj, @@ -378,11 +391,11 @@ static int sysupgrade(struct ubus_context *ctx, struct ubus_object *obj, return UBUS_STATUS_INVALID_ARGUMENT; blobmsg_parse(sysupgrade_policy, __SYSUPGRADE_MAX, tb, blob_data(msg), blob_len(msg)); - if (!tb[SYSUPGRADE_PATH]) + if (!tb[SYSUPGRADE_PATH] || !tb[SYSUPGRADE_PREFIX]) return UBUS_STATUS_INVALID_ARGUMENT; - procd_spawn_upgraded(blobmsg_get_string(tb[SYSUPGRADE_PATH])); - fprintf(stderr, "Yikees, something went wrong. no /sbin/upgraded ?\n"); + procd_exec_upgraded(blobmsg_get_string(tb[SYSUPGRADE_PREFIX]), + blobmsg_get_string(tb[SYSUPGRADE_PATH])); return 0; } diff --git a/upgraded/CMakeLists.txt b/upgraded/CMakeLists.txt index 093dba2..00d8ce5 100644 --- a/upgraded/CMakeLists.txt +++ b/upgraded/CMakeLists.txt @@ -2,16 +2,8 @@ cmake_minimum_required(VERSION 2.6) PROJECT(upgraded C) ADD_DEFINITIONS(-Os -ggdb -Wall -Werror --std=gnu99 -Wmissing-declarations) -set(CMAKE_EXE_LINKER_FLAGS "-static -fPIC") -set(CMAKE_FIND_LIBRARY_SUFFIXES .a) -set(CMAKE_EXE_LINK_DYNAMIC_C_FLAGS) -set(CMAKE_EXE_LINK_DYNAMIC_CXX_FLAGS) -set(CMAKE_SHARED_LIBRARY_C_FLAGS) -set(CMAKE_SHARED_LIBRARY_CXX_FLAGS) -set(CMAKE_SHARED_LIBRARY_LINK_C_FLAGS) -set(CMAKE_SHARED_LIBRARY_LINK_CXX_FLAGS) ADD_EXECUTABLE(upgraded upgraded.c ../watchdog.c) -TARGET_LINK_LIBRARIES(upgraded ubox rt -lc -lgcc_pic) +TARGET_LINK_LIBRARIES(upgraded ubox) INSTALL(TARGETS upgraded RUNTIME DESTINATION sbin ) diff --git a/upgraded/upgraded.c b/upgraded/upgraded.c index d7433e7..aa0b4ff 100644 --- a/upgraded/upgraded.c +++ b/upgraded/upgraded.c @@ -14,6 +14,7 @@ #include +#include #include #include #include @@ -24,6 +25,10 @@ #include "../watchdog.h" +#ifndef O_PATH +#define O_PATH 010000000 +#endif + static struct uloop_process upgrade_proc; unsigned int debug = 2; @@ -34,7 +39,7 @@ static void upgrade_proc_cb(struct uloop_process *proc, int ret) uloop_end(); } -static void sysupgarde(char *folder) +static void sysupgrade(char *folder) { char *args[] = { "/sbin/sysupgrade", "nand", NULL, NULL }; @@ -47,7 +52,7 @@ static void sysupgarde(char *folder) exit(-1); } if (upgrade_proc.pid <= 0) { - fprintf(stderr, "Failed to start sysupgarde\n"); + fprintf(stderr, "Failed to start sysupgrade\n"); uloop_end(); } } @@ -60,10 +65,21 @@ int main(int argc, char **argv) fprintf(stderr, "this tool needs to run as pid 1\n"); return -1; } - if (chdir("/tmp") == -1) { - fprintf(stderr, "failed to chdir to /tmp: %s\n", strerror(errno)); + + int fd = open("/", O_DIRECTORY|O_PATH); + if (fd < 0) { + fprintf(stderr, "unable to open prefix directory: %s\n", strerror(errno)); return -1; } + + chroot("."); + + if (fchdir(fd) == -1) { + fprintf(stderr, "failed to chdir to prefix directory: %s\n", strerror(errno)); + return -1; + } + close(fd); + if (argc != 2) { fprintf(stderr, "sysupgrade stage 2 failed, no folder specified\n"); return -1; @@ -71,7 +87,7 @@ int main(int argc, char **argv) uloop_init(); watchdog_init(0); - sysupgarde(argv[1]); + sysupgrade(argv[1]); uloop_run(); reboot(RB_AUTOBOOT); diff --git a/watchdog.c b/watchdog.c index 592ae7e..780b321 100644 --- a/watchdog.c +++ b/watchdog.c @@ -126,10 +126,15 @@ void watchdog_init(int preinit) } -void watchdog_no_cloexec(void) +void watchdog_set_cloexec(bool val) { if (wdt_fd < 0) return; - fcntl(wdt_fd, F_SETFD, fcntl(wdt_fd, F_GETFD) & ~FD_CLOEXEC); + int flags = fcntl(wdt_fd, F_GETFD); + if (val) + flags |= FD_CLOEXEC; + else + flags &= ~FD_CLOEXEC; + fcntl(wdt_fd, F_SETFD, flags); } diff --git a/watchdog.h b/watchdog.h index e5c696a..641e7e1 100644 --- a/watchdog.h +++ b/watchdog.h @@ -22,7 +22,7 @@ int watchdog_timeout(int timeout); int watchdog_frequency(int frequency); void watchdog_set_stopped(bool val); bool watchdog_get_stopped(void); -void watchdog_no_cloexec(void); +void watchdog_set_cloexec(bool val); void watchdog_ping(void); #else static inline void watchdog_init(int preinit) @@ -53,7 +53,7 @@ static inline bool watchdog_get_stopped(void) return true; } -static inline void watchdog_no_cloexec(void) +static inline void watchdog_set_cloexec(bool val) { } -- 2.25.1