diff options
Diffstat (limited to 'darwin-bootstrap/posixspawn-hook.c')
| -rw-r--r-- | darwin-bootstrap/posixspawn-hook.c | 102 |
1 files changed, 71 insertions, 31 deletions
diff --git a/darwin-bootstrap/posixspawn-hook.c b/darwin-bootstrap/posixspawn-hook.c index 5acb30b..e948b16 100644 --- a/darwin-bootstrap/posixspawn-hook.c +++ b/darwin-bootstrap/posixspawn-hook.c @@ -1,12 +1,20 @@ /* This library is loaded into launchd, and from there into xpcproxy, which - * launchd (always?) uses as an intermediary to exec its processes; its main - * purpose is to ensure that bundle-loader.dylib is specified in - * DYLD_INSERT_LIBRARIES when launching such processes. In the interests of - * not making ssh really weird (and because it's what Substrate does), this is - * separate from bundle-loader itself, so any processes that do their own - * spawning won't get the environment override. + * launchd uses as an intermediary to exec its processes; its main purpose is + * to ensure that bundle-loader.dylib is specified in DYLD_INSERT_LIBRARIES + * when launching such processes. In the interests of not making ssh really + * weird (and because it's what Substrate does), this is separate from + * bundle-loader itself, so any processes that do their own spawning won't get + * the environment override (though D_I_L will be inherited if the environment + * isn't reset). * - * It also handles the sandbox override for substituted. */ + * It also handles the sandbox override for substituted. + * + * Note: Because bundle-loader synchronously contacts substituted, it must not + * be loaded into any synchronous stuff launchd runs before starting jobs + * proper. Therefore, it's only inserted if the spawning process is xpcproxy + * (rather than launchd directly). I don't think iOS 7 does this yet, so this + * needs to be fixed there. + */ #define IB_LOG_NAME "posixspawn-hook" #include "ib-log.h" @@ -20,7 +28,6 @@ #include <sys/wait.h> #include <syslog.h> #include <malloc/malloc.h> -#include <assert.h> #include <errno.h> #include <arpa/inet.h> #include <libkern/OSByteOrder.h> @@ -30,7 +37,10 @@ extern char ***_NSGetEnviron(void); static __typeof__(posix_spawn) *old_posix_spawn, *old_posix_spawnp, hook_posix_spawn, hook_posix_spawnp; static __typeof__(wait4) *old_wait4, hook_wait4; -static __typeof__(waitpid) *old_waitpid, hook_waitpid; +static typeof(waitpid) *old_waitpid, hook_waitpid; +static int (*old_sandbox_check)(pid_t, const char *, int type, ...); + +static bool is_launchd; static bool advance(char **strp, const char *template) { size_t len = strlen(template); @@ -144,6 +154,34 @@ static int hook_posix_spawn_generic(__typeof__(posix_spawn) *old, char *const *my_envp = envp ? envp : *_NSGetEnviron(); posix_spawnattr_t my_attr = NULL; + short flags = 0; + if (posix_spawnattr_getflags(attrp, &flags)) + goto crap; + + if (IB_VERBOSE) { + ib_log("hook_posix_spawn_generic: path=%s%s%s", + path, + (flags & POSIX_SPAWN_SETEXEC) ? " (exec)" : "", + (flags & POSIX_SPAWN_START_SUSPENDED) ? " (suspend)" : ""); + for (char *const *ap = argv; *ap; ap++) + ib_log(" %s", *ap); + } + + + static const char bl_dylib[] = + "/Library/Substitute/bundle-loader.dylib"; + static const char psh_dylib[] = + "/Library/Substitute/posixspawn-hook.dylib"; + + /* which dylib should we add, if any? */ + const char *dylib_to_add; + if (!is_launchd) + dylib_to_add = bl_dylib; + else if (!strcmp(path, "/usr/libexec/xpcproxy")) + dylib_to_add = psh_dylib; + else + goto skip; + if (attrp) { posix_spawnattr_t attr = *attrp; size_t size = malloc_size(attr); @@ -155,31 +193,13 @@ static int hook_posix_spawn_generic(__typeof__(posix_spawn) *old, if (posix_spawnattr_init(&my_attr)) goto crap; } - - short flags; - if (posix_spawnattr_getflags(&my_attr, &flags)) - goto crap; - if (IB_VERBOSE) { - ib_log("hook_posix_spawn_generic: path=%s%s%s", - path, - (flags & POSIX_SPAWN_SETEXEC) ? " (exec)" : "", - (flags & POSIX_SPAWN_START_SUSPENDED) ? " (suspend)" : ""); - for (char *const *ap = argv; *ap; ap++) - ib_log(" %s", *ap); - } - /* This mirrors Substrate's logic with safe mode. I don't really * understand the point of the difference between its 'safe' (which removes * Substrate from DYLD_INSERT_LIBRARIES) and 'quit' (which just skips * directly to the original spawn), but I guess I'll just do the same for * maximum safety... */ bool safe_mode = false; - const char *orig_dyld_insert = ""; - static const char bl_dylib[] = - "/Library/Substitute/bundle-loader.dylib"; - static const char psh_dylib[] = - "/Library/Substitute/posixspawn-hook.dylib"; size_t env_count = 0; for (char *const *ep = my_envp; *ep; ep++) { env_count++; @@ -223,9 +243,6 @@ static int hook_posix_spawn_generic(__typeof__(posix_spawn) *old, if (!safe_mode) { if (newp != newp_orig) *newp++ = ':'; - const char *dylib_to_add = !strcmp(path, "/usr/libexec/xpcproxy") - ? psh_dylib - : bl_dylib; newp = stpcpy(newp, dylib_to_add); } if (IB_VERBOSE) @@ -335,6 +352,26 @@ pid_t hook_waitpid(pid_t pid, int *stat_loc, int options) { return ret; } +int hook_sandbox_check(pid_t pid, const char *op, int type, ...) { + /* Can't easily determine the number of arguments, so just assume there's + * less than 5 pointers' worth. */ + va_list ap; + va_start(ap, type); + long blah[5]; + for (int i = 0; i < 5; i++) + blah[i] = va_arg(ap, long); + va_end(ap); + if (!strcmp(op, "mach-lookup")) { + const char *name = (void *) blah[0]; + if (!strcmp(name, "com.ex.substituted")) { + /* always allow */ + return 0; + } + } + return old_sandbox_check(pid, op, type, + blah[0], blah[1], blah[2], blah[3], blah[4]); +} + void substitute_init(struct shuttle *shuttle, size_t nshuttle) { /* Just tell them we're done */ if (nshuttle != 1) { @@ -372,7 +409,9 @@ static void init() { * disk...) */ - struct substitute_image *im = substitute_open_image(_dyld_get_image_name(0)); + const char *image0 = _dyld_get_image_name(0); + is_launchd = !!strstr(image0, "launchd"); + struct substitute_image *im = substitute_open_image(image0); if (!im) { ib_log("posixspawn-hook: substitute_open_image failed"); goto end; @@ -383,6 +422,7 @@ static void init() { {"_posix_spawnp", hook_posix_spawnp, &old_posix_spawnp}, {"_waitpid", hook_waitpid, &old_waitpid}, {"_wait4", hook_wait4, &old_wait4}, + {"_sandbox_check", hook_sandbox_check, &old_sandbox_check}, }; int err = substitute_interpose_imports(im, hooks, sizeof(hooks)/sizeof(*hooks), 0); |