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Make sanitize_environ work properly

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topjohnwu 2021-09-18 05:11:10 -07:00
parent db590091b3
commit 63cfe7b47b
2 changed files with 22 additions and 19 deletions
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3
native/jni/magiskpolicy/rules.cpp
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@ -165,6 +165,9 @@ void sepolicy::magisk_rules() {
// For changing file context
allow("rootfs", "tmpfs", "filesystem", "associate");
// Allow Zygisk to prctl PR_SET_MM
allow("zygote", "zygote", "capability", "sys_resource");
// Allow update_engine/addon.d-v2 to run permissive on all ROMs
permissive("update_engine");

36
native/jni/zygisk/entry.cpp
View File

@ -54,25 +54,26 @@ static void *unload_first_stage(void *v) {
return nullptr;
}
// Make sure /proc/self/environ does not reveal our secrets
// Copy all env to a contiguous memory and set the memory region as MM_ENV
// Make sure /proc/self/environ is sanitized
// Filter env and reset MM_ENV_END
static void sanitize_environ() {
static string env;
char *cur = environ[0];
for (int i = 0; environ[i]; ++i) {
if (str_starts(environ[i], INJECT_ENV_1 "="))
if (str_starts(environ[i], INJECT_ENV_1 "=")) {
// This specific env has to live in heap
environ[i] = strdup(environ[i]);
continue;
env += environ[i];
env += '\0';
}
for (int i = 0; i < 2; ++i) {
bool success = true;
success &= (0 <= prctl(PR_SET_MM, PR_SET_MM_ENV_START, env.data(), 0, 0));
success &= (0 <= prctl(PR_SET_MM, PR_SET_MM_ENV_END, env.data() + env.size(), 0, 0));
if (success)
break;
// Copy all filtered env onto the original stack
int len = strlen(environ[i]);
memmove(cur, environ[i], len + 1);
environ[i] = cur;
cur += len + 1;
}
prctl(PR_SET_MM, PR_SET_MM_ENV_END, cur, 0, 0);
}
__attribute__((destructor))
@ -108,24 +109,23 @@ static void inject_init() {
// Update path to 1st stage lib
*(strrchr(env, '.') - 1) = '1';
// Some cleanup
sanitize_environ();
active_threads++;
new_daemon_thread(&unload_first_stage, env);
} else if (getenv(INJECT_ENV_1)) {
android_logging();
LOGD("zygisk: inject 1st stage\n");
char *ld = getenv("LD_PRELOAD");
string ld = getenv("LD_PRELOAD");
char *path;
if (char *c = strrchr(ld, ':')) {
if (char *c = strrchr(ld.data(), ':')) {
*c = '\0';
setenv("LD_PRELOAD", ld, 1); // Restore original LD_PRELOAD
setenv("LD_PRELOAD", ld.data(), 1); // Restore original LD_PRELOAD
path = c + 1;
} else {
unsetenv("LD_PRELOAD");
path = ld;
path = ld.data();
}
sanitize_environ();
// Update path to 2nd stage lib
*(strrchr(path, '.') - 1) = '2';