mirror of
https://github.com/podman-container-tools/podman.git
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3481dd492f
Bump go.podman.io/buildah to b05874667205b40322adce5949ab0967f4e913ef to incorporate fixes from GHSA-3528-5p26-cf44. Signed-off-by: Nalin Dahyabhai <nalin@redhat.com>
101 lines
3 KiB
Go
101 lines
3 KiB
Go
package userns
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import (
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"bufio"
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"errors"
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"fmt"
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"os"
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"sync"
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"syscall"
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)
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// See PROC_USER_INIT_INO in https://github.com/torvalds/linux/blob/v7.1/include/uapi/linux/nsfs.h#L50.
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const procUserInitIno = 0xEFFFFFFD
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var inUserNS = sync.OnceValue(runningInUserNS)
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// runningInUserNS detects whether we are currently running in a user namespace.
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//
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// This code was migrated from [libcontainer/runc] and based on an implementation
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// from [lcx/incus].
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//
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// [libcontainer/runc]: https://github.com/opencontainers/runc/blob/3778ae603c706494fd1e2c2faf83b406e38d687d/libcontainer/userns/userns_linux.go#L12-L49
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// [lcx/incus]: https://github.com/lxc/incus/blob/e45085dd42f826b3c8c3228e9733c0b6f998eafe/shared/util.go#L678-L700
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func runningInUserNS() bool {
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var st syscall.Stat_t
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if err := syscall.Stat("/proc/self/ns/user", &st); err == nil {
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// The kernel's initial user namespace inode is definitive when it
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// matches. OpenVZ virtualizes namespace inode numbers, so a mismatch
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// must fall back to uid_map-based detection there.
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if st.Ino == procUserInitIno {
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return false
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}
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if runningInOpenVZ() {
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return runningInUserNSFromUIDMap()
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}
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return true
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} else if !os.IsNotExist(err) {
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// As long as /proc/self/ns/user exists, we are on a modern kernel.
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// Other errors indicate an unexpected procfs state, where assuming the
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// init namespace would be unsafe.
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return false
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}
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// Only fall back for older kernels that do not expose the user namespace
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// through procfs at /proc/self/ns/user.
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// TODO: Remove this fallback once Linux kernels older than 3.8 are no
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// longer supported.
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return runningInUserNSFromUIDMap()
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}
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func runningInUserNSFromUIDMap() bool {
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file, err := os.Open("/proc/self/uid_map")
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if err != nil {
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// This kernel-provided file only exists if user namespaces are supported.
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return false
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}
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defer file.Close()
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buf := bufio.NewReader(file)
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l, _, err := buf.ReadLine()
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if err != nil {
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return false
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}
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return uidMapInUserNS(string(l))
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}
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func uidMapInUserNS(uidMap string) bool {
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if uidMap == "" {
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// File exist but empty (the initial state when userns is created,
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// see user_namespaces(7)).
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return true
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}
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var a, b, c int64
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if _, err := fmt.Sscanf(uidMap, "%d %d %d", &a, &b, &c); err != nil {
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// Assume we are in a regular, non user namespace.
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return false
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}
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// As per user_namespaces(7), /proc/self/uid_map of
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// the initial user namespace shows 0 0 4294967295.
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initNS := a == 0 && b == 0 && c == 4294967295
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return !initNS
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}
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// runningInOpenVZ reports whether the process is running inside an OpenVZ
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// container.
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//
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// OpenVZ exposes /proc/vz both on the host and inside containers, while
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// /proc/bc is only exposed on the host. This follows systemd's OpenVZ
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// detection:
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// https://github.com/systemd/systemd/blob/v261.2/src/basic/virt.c#L642-L653
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func runningInOpenVZ() bool {
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var st syscall.Stat_t
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if err := syscall.Stat("/proc/vz", &st); err != nil {
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return false
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}
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err := syscall.Stat("/proc/bc", &st)
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return errors.Is(err, syscall.ENOENT)
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}
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