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authorGiuseppe Scrivano <gscrivan@redhat.com>2021-04-19 12:21:26 +0200
committerGiuseppe Scrivano <gscrivan@redhat.com>2021-04-26 08:58:54 +0200
commite4c269e2d01dee6497269e62119126b93e388da3 (patch)
treee32c758175714d1136494282631e33db409ad875
parent24f00e4695003c923915b7721dd4e96b844539ee (diff)
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rootless: attempt to copy current mappings first
when creating a user namespace, attempt to create it first by copying the current mappings and then fallback to the other methods: 1) use newidmap tools and ... 2) create a user namespace with a single user mapped. Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>
-rw-r--r--pkg/rootless/rootless_linux.go58
1 files changed, 51 insertions, 7 deletions
diff --git a/pkg/rootless/rootless_linux.go b/pkg/rootless/rootless_linux.go
index 83d4d7281..fdfeed854 100644
--- a/pkg/rootless/rootless_linux.go
+++ b/pkg/rootless/rootless_linux.go
@@ -4,6 +4,7 @@ package rootless
import (
"bufio"
+ "bytes"
"fmt"
"io"
"io/ioutil"
@@ -18,6 +19,7 @@ import (
"github.com/containers/podman/v3/pkg/errorhandling"
"github.com/containers/storage/pkg/idtools"
+ "github.com/containers/storage/pkg/unshare"
"github.com/pkg/errors"
"github.com/sirupsen/logrus"
"golang.org/x/sys/unix"
@@ -67,6 +69,15 @@ func IsRootless() bool {
}
}
isRootless = os.Geteuid() != 0 || os.Getenv("_CONTAINERS_USERNS_CONFIGURED") != ""
+ if !isRootless {
+ hasCapSysAdmin, err := unshare.HasCapSysAdmin()
+ if err != nil {
+ logrus.Warnf("failed to read CAP_SYS_ADMIN presence for the current process")
+ }
+ if err == nil && !hasCapSysAdmin {
+ isRootless = true
+ }
+ }
})
return isRootless
}
@@ -142,8 +153,12 @@ func tryMappingTool(uid bool, pid int, hostID int, mappings []idtools.IDMap) err
// namespace of the specified PID without looking up its parent. Useful to join directly
// the conmon process.
func joinUserAndMountNS(pid uint, pausePid string) (bool, int, error) {
- if os.Geteuid() == 0 || os.Getenv("_CONTAINERS_USERNS_CONFIGURED") != "" {
- return false, -1, nil
+ hasCapSysAdmin, err := unshare.HasCapSysAdmin()
+ if err != nil {
+ return false, 0, err
+ }
+ if hasCapSysAdmin || os.Getenv("_CONTAINERS_USERNS_CONFIGURED") != "" {
+ return false, 0, nil
}
cPausePid := C.CString(pausePid)
@@ -192,8 +207,28 @@ func GetConfiguredMappings() ([]idtools.IDMap, []idtools.IDMap, error) {
return uids, gids, nil
}
+func copyMappings(from, to string) error {
+ content, err := ioutil.ReadFile(from)
+ if err != nil {
+ return err
+ }
+ // Both runc and crun check whether the current process is in a user namespace
+ // by looking up 4294967295 in /proc/self/uid_map. If the mappings would be
+ // copied as they are, the check in the OCI runtimes would fail. So just split
+ // it in two different ranges.
+ if bytes.Contains(content, []byte("4294967295")) {
+ content = []byte("0 0 1\n1 1 4294967294\n")
+ }
+ return ioutil.WriteFile(to, content, 0600)
+}
+
func becomeRootInUserNS(pausePid, fileToRead string, fileOutput *os.File) (_ bool, _ int, retErr error) {
- if os.Geteuid() == 0 || os.Getenv("_CONTAINERS_USERNS_CONFIGURED") != "" {
+ hasCapSysAdmin, err := unshare.HasCapSysAdmin()
+ if err != nil {
+ return false, 0, err
+ }
+
+ if hasCapSysAdmin || os.Getenv("_CONTAINERS_USERNS_CONFIGURED") != "" {
if os.Getenv("_CONTAINERS_USERNS_CONFIGURED") == "init" {
return false, 0, runInUser()
}
@@ -250,8 +285,16 @@ func becomeRootInUserNS(pausePid, fileToRead string, fileOutput *os.File) (_ boo
return false, -1, err
}
+ uidMap := fmt.Sprintf("/proc/%d/uid_map", pid)
+ gidMap := fmt.Sprintf("/proc/%d/gid_map", pid)
+
uidsMapped := false
- if uids != nil {
+
+ if err := copyMappings("/proc/self/uid_map", uidMap); err == nil {
+ uidsMapped = true
+ }
+
+ if uids != nil && !uidsMapped {
err := tryMappingTool(true, pid, os.Geteuid(), uids)
// If some mappings were specified, do not ignore the error
if err != nil && len(uids) > 0 {
@@ -268,7 +311,6 @@ func becomeRootInUserNS(pausePid, fileToRead string, fileOutput *os.File) (_ boo
}
logrus.Debugf("write setgroups file exited with 0")
- uidMap := fmt.Sprintf("/proc/%d/uid_map", pid)
err = ioutil.WriteFile(uidMap, []byte(fmt.Sprintf("%d %d 1\n", 0, os.Geteuid())), 0666)
if err != nil {
return false, -1, errors.Wrapf(err, "cannot write uid_map")
@@ -277,7 +319,10 @@ func becomeRootInUserNS(pausePid, fileToRead string, fileOutput *os.File) (_ boo
}
gidsMapped := false
- if gids != nil {
+ if err := copyMappings("/proc/self/gid_map", gidMap); err == nil {
+ gidsMapped = true
+ }
+ if gids != nil && !gidsMapped {
err := tryMappingTool(false, pid, os.Getegid(), gids)
// If some mappings were specified, do not ignore the error
if err != nil && len(gids) > 0 {
@@ -286,7 +331,6 @@ func becomeRootInUserNS(pausePid, fileToRead string, fileOutput *os.File) (_ boo
gidsMapped = err == nil
}
if !gidsMapped {
- gidMap := fmt.Sprintf("/proc/%d/gid_map", pid)
err = ioutil.WriteFile(gidMap, []byte(fmt.Sprintf("%d %d 1\n", 0, os.Getegid())), 0666)
if err != nil {
return false, -1, errors.Wrapf(err, "cannot write gid_map")