mirror of
https://github.com/privatevoid-net/nix-super.git
synced 2024-09-21 00:48:04 +03:00
98 lines
2.7 KiB
C++
98 lines
2.7 KiB
C++
#if __linux__
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#include "namespaces.hh"
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#include "util.hh"
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#include "finally.hh"
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#include <sys/mount.h>
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namespace nix {
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bool userNamespacesSupported()
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{
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static auto res = [&]() -> bool
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{
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if (!pathExists("/proc/self/ns/user")) {
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debug("'/proc/self/ns/user' does not exist; your kernel was likely built without CONFIG_USER_NS=y");
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return false;
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}
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Path maxUserNamespaces = "/proc/sys/user/max_user_namespaces";
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if (!pathExists(maxUserNamespaces) ||
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trim(readFile(maxUserNamespaces)) == "0")
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{
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debug("user namespaces appear to be disabled; check '/proc/sys/user/max_user_namespaces'");
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return false;
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}
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Path procSysKernelUnprivilegedUsernsClone = "/proc/sys/kernel/unprivileged_userns_clone";
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if (pathExists(procSysKernelUnprivilegedUsernsClone)
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&& trim(readFile(procSysKernelUnprivilegedUsernsClone)) == "0")
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{
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debug("user namespaces appear to be disabled; check '/proc/sys/kernel/unprivileged_userns_clone'");
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return false;
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}
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try {
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Pid pid = startProcess([&]()
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{
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_exit(0);
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}, {
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.cloneFlags = CLONE_NEWUSER
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});
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auto r = pid.wait();
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assert(!r);
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} catch (SysError & e) {
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debug("user namespaces do not work on this system: %s", e.msg());
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return false;
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}
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return true;
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}();
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return res;
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}
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bool mountAndPidNamespacesSupported()
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{
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static auto res = [&]() -> bool
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{
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try {
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Pid pid = startProcess([&]()
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{
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/* Make sure we don't remount the parent's /proc. */
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if (mount(0, "/", 0, MS_PRIVATE | MS_REC, 0) == -1)
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_exit(1);
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/* Test whether we can remount /proc. The kernel disallows
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this if /proc is not fully visible, i.e. if there are
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filesystems mounted on top of files inside /proc. See
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https://lore.kernel.org/lkml/87tvsrjai0.fsf@xmission.com/T/. */
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if (mount("none", "/proc", "proc", 0, 0) == -1)
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_exit(2);
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_exit(0);
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}, {
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.cloneFlags = CLONE_NEWNS | CLONE_NEWPID | (userNamespacesSupported() ? CLONE_NEWUSER : 0)
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});
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if (pid.wait()) {
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debug("PID namespaces do not work on this system: cannot remount /proc");
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return false;
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}
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} catch (SysError & e) {
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debug("mount namespaces do not work on this system: %s", e.msg());
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return false;
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}
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return true;
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}();
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return res;
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}
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}
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#endif
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