int main(int argc, char **argv)
{
if (argc <= 1) {
fprintf(stderr, "Usage: %s <renderer process> <args...>\n", argv[0]);
return EXIT_FAILURE;
}
if (MoveToNewPIDNamespace())
return EXIT_FAILURE;
if (SpawnChrootHelper())
return EXIT_FAILURE;
if (DropRoot())
return EXIT_FAILURE;
if (SetupChildEnvironment())
return EXIT_FAILURE;
execv(argv[1], &argv[1]);
_err(EXIT_FAILURE, "execv failed");
return EXIT_FAILURE;
}
int main(int argc, char** argv) {
if (argc <= 1) {
if (argc <= 0) {
return 1;
}
fprintf(stderr, "Usage: %s <renderer process> <args...>\n", argv[0]);
return 1;
}
// Allow someone to query our API version
if (argc == 2 && 0 == strcmp(argv[1], kSuidSandboxGetApiSwitch)) {
printf("%ld\n", kSUIDSandboxApiNumber);
return 0;
}
// We cannot adjust /proc/pid/oom_adj for sandboxed renderers
// because those files are owned by root. So we need a helper here.
if (argc == 4 && (0 == strcmp(argv[1], kAdjustOOMScoreSwitch))) {
char* endptr = NULL;
long score;
errno = 0;
unsigned long pid_ul = strtoul(argv[2], &endptr, 10);
if (pid_ul == ULONG_MAX || !endptr || *endptr || errno != 0)
return 1;
pid_t pid = pid_ul;
endptr = NULL;
errno = 0;
score = strtol(argv[3], &endptr, 10);
if (score == LONG_MAX || score == LONG_MIN || !endptr || *endptr ||
errno != 0) {
return 1;
}
return AdjustOOMScore(pid, score);
}
// Protect the core setuid sandbox functionality with an API version
if (!CheckAndExportApiVersion()) {
return 1;
}
if (geteuid() != 0) {
fprintf(stderr,
"The setuid sandbox is not running as root. Common causes:\n"
" * An unprivileged process using ptrace on it, like a debugger.\n"
" * A parent process set prctl(PR_SET_NO_NEW_PRIVS, ...)\n");
}
if (!MoveToNewNamespaces())
return 1;
if (!SpawnChrootHelper())
return 1;
if (!DropRoot())
return 1;
if (!SetupChildEnvironment())
return 1;
execv(argv[1], &argv[1]);
FatalError("execv failed");
return 1;
}
static bool MoveToNewNamespaces() {
// These are the sets of flags which we'll try, in order.
const int kCloneExtraFlags[] = {CLONE_NEWPID | CLONE_NEWNET, CLONE_NEWPID, };
// We need to close kZygoteIdFd before the child can continue. We use this
// socketpair to tell the child when to continue;
int sync_fds[2];
if (socketpair(AF_UNIX, SOCK_STREAM, 0, sync_fds)) {
FatalError("Failed to create a socketpair");
}
for (size_t i = 0; i < sizeof(kCloneExtraFlags) / sizeof(kCloneExtraFlags[0]);
i++) {
pid_t pid = syscall(__NR_clone, SIGCHLD | kCloneExtraFlags[i], 0, 0, 0);
const int clone_errno = errno;
if (pid > 0) {
if (!DropRoot()) {
FatalError("Could not drop privileges");
} else {
if (close(sync_fds[0]) || shutdown(sync_fds[1], SHUT_RD))
FatalError("Could not close socketpair");
// The kZygoteIdFd needs to be closed in the parent before
// Zygote gets started.
if (close(kZygoteIdFd))
FatalError("close");
// Tell our child to continue
if (HANDLE_EINTR(send(sync_fds[1], "C", 1, MSG_NOSIGNAL)) != 1)
FatalError("send");
if (close(sync_fds[1]))
FatalError("close");
// We want to keep a full process tree and we don't want our childs to
// be reparented to (the outer PID namespace) init. So we wait for it.
WaitForChildAndExit(pid);
}
// NOTREACHED
FatalError("Not reached");
}
if (pid == 0) {
if (close(sync_fds[1]) || shutdown(sync_fds[0], SHUT_WR))
FatalError("Could not close socketpair");
// Wait for the parent to confirm it closed kZygoteIdFd before we
// continue
char should_continue;
if (HANDLE_EINTR(read(sync_fds[0], &should_continue, 1)) != 1)
FatalError("Read on socketpair");
if (close(sync_fds[0]))
FatalError("close");
if (kCloneExtraFlags[i] & CLONE_NEWPID) {
setenv(kSandboxPIDNSEnvironmentVarName, "", 1 /* overwrite */);
} else {
unsetenv(kSandboxPIDNSEnvironmentVarName);
}
if (kCloneExtraFlags[i] & CLONE_NEWNET) {
setenv(kSandboxNETNSEnvironmentVarName, "", 1 /* overwrite */);
} else {
unsetenv(kSandboxNETNSEnvironmentVarName);
}
break;
}
// If EINVAL then the system doesn't support the requested flags, so
// continue to try a different set.
// On any other errno value the system *does* support these flags but
// something went wrong, hence we bail with an error message rather then
// provide less security.
if (errno != EINVAL) {
fprintf(stderr, "Failed to move to new namespace:");
if (kCloneExtraFlags[i] & CLONE_NEWPID) {
fprintf(stderr, " PID namespaces supported,");
}
if (kCloneExtraFlags[i] & CLONE_NEWNET) {
fprintf(stderr, " Network namespace supported,");
}
fprintf(stderr, " but failed: errno = %s\n", strerror(clone_errno));
return false;
}
}
// If the system doesn't support NEWPID then we carry on anyway.
return true;
}
int main(int argc, char **argv) {
if (argc <= 1) {
if (argc <= 0) {
return 1;
}
fprintf(stderr, "Usage: %s <renderer process> <args...>\n", argv[0]);
return 1;
}
// Allow someone to query our API version
if (argc == 2 && 0 == strcmp(argv[1], kSuidSandboxGetApiSwitch)) {
printf("%ld\n", kSUIDSandboxApiNumber);
return 0;
}
// In the SUID sandbox, if we succeed in calling MoveToNewNamespaces()
// below, then the zygote and all the renderers are in an alternate PID
// namespace and do not know their real PIDs. As such, they report the wrong
// PIDs to the task manager.
//
// To fix this, when the zygote spawns a new renderer, it gives the renderer
// a dummy socket, which has a unique inode number. Then it asks the sandbox
// host to find the PID of the process holding that fd by searching /proc.
//
// Since the zygote and renderers are all spawned by this setuid executable,
// their entries in /proc are owned by root and only readable by root. In
// order to search /proc for the fd we want, this setuid executable has to
// double as a helper and perform the search. The code block below does this
// when you call it with --find-inode INODE_NUMBER.
if (argc == 3 && (0 == strcmp(argv[1], kFindInodeSwitch))) {
pid_t pid;
char* endptr = NULL;
errno = 0;
ino_t inode = strtoull(argv[2], &endptr, 10);
if (inode == ULLONG_MAX || !endptr || *endptr || errno != 0)
return 1;
if (!FindProcessHoldingSocket(&pid, inode))
return 1;
printf("%d\n", pid);
return 0;
}
// Likewise, we cannot adjust /proc/pid/oom_adj for sandboxed renderers
// because those files are owned by root. So we need another helper here.
if (argc == 4 && (0 == strcmp(argv[1], kAdjustOOMScoreSwitch))) {
char* endptr = NULL;
long score;
errno = 0;
unsigned long pid_ul = strtoul(argv[2], &endptr, 10);
if (pid_ul == ULONG_MAX || !endptr || *endptr || errno != 0)
return 1;
pid_t pid = pid_ul;
endptr = NULL;
errno = 0;
score = strtol(argv[3], &endptr, 10);
if (score == LONG_MAX || score == LONG_MIN ||
!endptr || *endptr || errno != 0)
return 1;
return AdjustOOMScore(pid, score);
}
#if defined(OS_CHROMEOS)
if (argc == 3 && (0 == strcmp(argv[1], kAdjustLowMemMarginSwitch))) {
char* endptr = NULL;
errno = 0;
unsigned long margin_mb = strtoul(argv[2], &endptr, 10);
if (!endptr || *endptr || errno != 0)
return 1;
return AdjustLowMemoryMargin(margin_mb);
}
#endif
// Protect the core setuid sandbox functionality with an API version
if (!CheckAndExportApiVersion()) {
return 1;
}
if (!MoveToNewNamespaces())
return 1;
if (!SpawnChrootHelper())
return 1;
if (!DropRoot())
return 1;
if (!SetupChildEnvironment())
return 1;
execv(argv[1], &argv[1]);
FatalError("execv failed");
return 1;
}
static bool MoveToNewNamespaces() {
// These are the sets of flags which we'll try, in order.
const int kCloneExtraFlags[] = {
CLONE_NEWPID | CLONE_NEWNET,
CLONE_NEWPID,
};
// We need to close kZygoteIdFd before the child can continue. We use this
// socketpair to tell the child when to continue;
int sync_fds[2];
if (socketpair(AF_UNIX, SOCK_STREAM, 0, sync_fds)) {
FatalError("Failed to create a socketpair");
}
for (size_t i = 0;
i < sizeof(kCloneExtraFlags) / sizeof(kCloneExtraFlags[0]);
i++) {
pid_t pid = syscall(__NR_clone, SIGCHLD | kCloneExtraFlags[i], 0, 0, 0);
if (pid > 0) {
if (!DropRoot()) {
FatalError("Could not drop privileges");
} else {
if (close(sync_fds[0]) || shutdown(sync_fds[1], SHUT_RD))
FatalError("Could not close socketpair");
// The kZygoteIdFd needs to be closed in the parent before
// Zygote gets started.
if (close(kZygoteIdFd))
FatalError("close");
// Tell our child to continue
if (HANDLE_EINTR(send(sync_fds[1], "C", 1, MSG_NOSIGNAL)) != 1)
FatalError("send");
if (close(sync_fds[1]))
FatalError("close");
// We want to keep a full process tree and we don't want our childs to
// be reparented to (the outer PID namespace) init. So we wait for it.
WaitForChildAndExit(pid);
}
// NOTREACHED
FatalError("Not reached");
}
if (pid == 0) {
if (close(sync_fds[1]) || shutdown(sync_fds[0], SHUT_WR))
FatalError("Could not close socketpair");
// Wait for the parent to confirm it closed kZygoteIdFd before we
// continue
char should_continue;
if (HANDLE_EINTR(read(sync_fds[0], &should_continue, 1)) != 1)
FatalError("Read on socketpair");
if (close(sync_fds[0]))
FatalError("close");
if (kCloneExtraFlags[i] & CLONE_NEWPID) {
setenv("SBX_PID_NS", "", 1 /* overwrite */);
} else {
unsetenv("SBX_PID_NS");
}
if (kCloneExtraFlags[i] & CLONE_NEWNET) {
setenv("SBX_NET_NS", "", 1 /* overwrite */);
} else {
unsetenv("SBX_NET_NS");
}
break;
}
if (errno != EINVAL) {
perror("Failed to move to new PID namespace");
return false;
}
}
// If the system doesn't support NEWPID then we carry on anyway.
return true;
}
