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Handle symlinks when checking DB vs runtime configs
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When Podman starts, it checks a number of critical runtime paths
against stored values in the database to make sure that existing
containers are not broken by a configuration change. We recently
made some changes to this logic to make our handling of the some
options more sane (StaticDir in particular was set based on other
passed options in a way that was not particularly sane) which has
made the logic more sensitive to paths with symlinks. As a simple
fix, handle symlinks properly in our DB vs runtime comparisons.

The BoltDB bits are uglier because very, very old Podman versions
sometimes did not stuff a proper value in the database and
instead used the empty string. SQLite is new enough that we don't
have to worry about such things.

Fixes #20872

Signed-off-by: Matt Heon <[email protected]>
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@mheon
mheon authored and openshift-cherrypick-robot committed Dec 3, 2023
1 parent 4635f40 commit 2d20d2e
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Showing 3 changed files with 89 additions and 21 deletions.
41 changes: 37 additions & 4 deletions libpod/boltdb_state_internal.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,9 @@
package libpod

import (
"errors"
"fmt"
"io/fs"
"os"
"path/filepath"
"runtime"
Expand Down Expand Up @@ -94,6 +96,7 @@ type dbConfigValidation struct {
runtimeValue string
key []byte
defaultValue string
isPath bool
}

// Check if the configuration of the database is compatible with the
Expand All @@ -112,42 +115,49 @@ func checkRuntimeConfig(db *bolt.DB, rt *Runtime) error {
runtime.GOOS,
osKey,
runtime.GOOS,
false,
},
{
"libpod root directory (staticdir)",
filepath.Clean(rt.config.Engine.StaticDir),
staticDirKey,
"",
true,
},
{
"libpod temporary files directory (tmpdir)",
filepath.Clean(rt.config.Engine.TmpDir),
tmpDirKey,
"",
true,
},
{
"storage temporary directory (runroot)",
filepath.Clean(rt.StorageConfig().RunRoot),
runRootKey,
storeOpts.RunRoot,
true,
},
{
"storage graph root directory (graphroot)",
filepath.Clean(rt.StorageConfig().GraphRoot),
graphRootKey,
storeOpts.GraphRoot,
true,
},
{
"storage graph driver",
rt.StorageConfig().GraphDriverName,
graphDriverKey,
storeOpts.GraphDriverName,
false,
},
{
"volume path",
rt.config.Engine.VolumePath,
volPathKey,
"",
true,
},
}

Expand Down Expand Up @@ -222,22 +232,45 @@ func readOnlyValidateConfig(bucket *bolt.Bucket, toCheck dbConfigValidation) (bo
}

dbValue := string(keyBytes)
ourValue := toCheck.runtimeValue

// Tolerate symlinks when possible - most relevant for OStree systems
// and rootless containers, where we want to put containers in /home,
// which is symlinked to /var/home.
if toCheck.isPath {
if dbValue != "" {
// Ignore ENOENT on both, on a fresh system some paths
// may not exist this early in Libpod init.
dbVal, err := filepath.EvalSymlinks(dbValue)
if err != nil && !errors.Is(err, fs.ErrNotExist) {
return false, fmt.Errorf("evaluating symlinks on DB %s path %q: %w", toCheck.name, dbValue, err)
}
dbValue = dbVal
}
if ourValue != "" {
ourVal, err := filepath.EvalSymlinks(ourValue)
if err != nil && !errors.Is(err, fs.ErrNotExist) {
return false, fmt.Errorf("evaluating symlinks on configured %s path %q: %w", toCheck.name, ourValue, err)
}
ourValue = ourVal
}
}

if toCheck.runtimeValue != dbValue {
if ourValue != dbValue {
// If the runtime value is the empty string and default is not,
// check against default.
if toCheck.runtimeValue == "" && toCheck.defaultValue != "" && dbValue == toCheck.defaultValue {
if ourValue == "" && toCheck.defaultValue != "" && dbValue == toCheck.defaultValue {
return true, nil
}

// If the DB value is the empty string, check that the runtime
// value is the default.
if dbValue == "" && toCheck.defaultValue != "" && toCheck.runtimeValue == toCheck.defaultValue {
if dbValue == "" && toCheck.defaultValue != "" && ourValue == toCheck.defaultValue {
return true, nil
}

return true, fmt.Errorf("database %s %q does not match our %s %q: %w",
toCheck.name, dbValue, toCheck.name, toCheck.runtimeValue, define.ErrDBBadConfig)
toCheck.name, dbValue, toCheck.name, ourValue, define.ErrDBBadConfig)
}

return true, nil
Expand Down
54 changes: 37 additions & 17 deletions libpod/sqlite_state.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,7 @@ import (
"database/sql"
"errors"
"fmt"
"io/fs"
"os"
"path/filepath"
goruntime "runtime"
Expand Down Expand Up @@ -316,14 +317,14 @@ func (s *SQLiteState) ValidateDBConfig(runtime *Runtime) (defErr error) {
);`

var (
os, staticDir, tmpDir, graphRoot, runRoot, graphDriver, volumePath string
runtimeOS = goruntime.GOOS
runtimeStaticDir = filepath.Clean(s.runtime.config.Engine.StaticDir)
runtimeTmpDir = filepath.Clean(s.runtime.config.Engine.TmpDir)
runtimeGraphRoot = filepath.Clean(s.runtime.StorageConfig().GraphRoot)
runtimeRunRoot = filepath.Clean(s.runtime.StorageConfig().RunRoot)
runtimeGraphDriver = s.runtime.StorageConfig().GraphDriverName
runtimeVolumePath = filepath.Clean(s.runtime.config.Engine.VolumePath)
dbOS, staticDir, tmpDir, graphRoot, runRoot, graphDriver, volumePath string
runtimeOS = goruntime.GOOS
runtimeStaticDir = filepath.Clean(s.runtime.config.Engine.StaticDir)
runtimeTmpDir = filepath.Clean(s.runtime.config.Engine.TmpDir)
runtimeGraphRoot = filepath.Clean(s.runtime.StorageConfig().GraphRoot)
runtimeRunRoot = filepath.Clean(s.runtime.StorageConfig().RunRoot)
runtimeGraphDriver = s.runtime.StorageConfig().GraphDriverName
runtimeVolumePath = filepath.Clean(s.runtime.config.Engine.VolumePath)
)

// Some fields may be empty, indicating they are set to the default.
Expand Down Expand Up @@ -360,7 +361,7 @@ func (s *SQLiteState) ValidateDBConfig(runtime *Runtime) (defErr error) {

row := tx.QueryRow("SELECT Os, StaticDir, TmpDir, GraphRoot, RunRoot, GraphDriver, VolumeDir FROM DBConfig;")

if err := row.Scan(&os, &staticDir, &tmpDir, &graphRoot, &runRoot, &graphDriver, &volumePath); err != nil {
if err := row.Scan(&dbOS, &staticDir, &tmpDir, &graphRoot, &runRoot, &graphDriver, &volumePath); err != nil {
if errors.Is(err, sql.ErrNoRows) {
if _, err := tx.Exec(createRow, 1, schemaVersion, runtimeOS,
runtimeStaticDir, runtimeTmpDir, runtimeGraphRoot,
Expand All @@ -378,33 +379,52 @@ func (s *SQLiteState) ValidateDBConfig(runtime *Runtime) (defErr error) {
return fmt.Errorf("retrieving DB config: %w", err)
}

checkField := func(fieldName, dbVal, ourVal string) error {
checkField := func(fieldName, dbVal, ourVal string, isPath bool) error {
if isPath {
// Evaluate symlinks. Ignore ENOENT. No guarantee all
// directories exist this early in Libpod init.
if dbVal != "" {
dbValClean, err := filepath.EvalSymlinks(dbVal)
if err != nil && !errors.Is(err, fs.ErrNotExist) {
return fmt.Errorf("cannot evaluate symlinks on DB %s path %q: %w", fieldName, dbVal, err)
}
dbVal = dbValClean
}
if ourVal != "" {
ourValClean, err := filepath.EvalSymlinks(ourVal)
if err != nil && !errors.Is(err, fs.ErrNotExist) {
return fmt.Errorf("cannot evaluate symlinks on our %s path %q: %w", fieldName, ourVal, err)
}
ourVal = ourValClean
}
}

if dbVal != ourVal {
return fmt.Errorf("database %s %q does not match our %s %q: %w", fieldName, dbVal, fieldName, ourVal, define.ErrDBBadConfig)
}

return nil
}

if err := checkField("os", os, runtimeOS); err != nil {
if err := checkField("os", dbOS, runtimeOS, false); err != nil {
return err
}
if err := checkField("static dir", staticDir, runtimeStaticDir); err != nil {
if err := checkField("static dir", staticDir, runtimeStaticDir, true); err != nil {
return err
}
if err := checkField("tmp dir", tmpDir, runtimeTmpDir); err != nil {
if err := checkField("tmp dir", tmpDir, runtimeTmpDir, true); err != nil {
return err
}
if err := checkField("graph root", graphRoot, runtimeGraphRoot); err != nil {
if err := checkField("graph root", graphRoot, runtimeGraphRoot, true); err != nil {
return err
}
if err := checkField("run root", runRoot, runtimeRunRoot); err != nil {
if err := checkField("run root", runRoot, runtimeRunRoot, true); err != nil {
return err
}
if err := checkField("graph driver", graphDriver, runtimeGraphDriver); err != nil {
if err := checkField("graph driver", graphDriver, runtimeGraphDriver, false); err != nil {
return err
}
if err := checkField("volume path", volumePath, runtimeVolumePath); err != nil {
if err := checkField("volume path", volumePath, runtimeVolumePath, true); err != nil {
return err
}

Expand Down
15 changes: 15 additions & 0 deletions test/system/005-info.bats
View file
Original file line number Diff line number Diff line change
Expand Up @@ -183,6 +183,21 @@ host.slirp4netns.executable | $expr_path
fi
}

@test "rootless podman with symlinked $HOME" {
# This is only needed as rootless, but we don't have a skip_if_root
# And it will not hurt to run as root.
skip_if_remote "path validation is only done in libpod, does not effect remote"

new_home=$PODMAN_TMPDIR/home

ln -s /home $new_home

# Just need the command to run cleanly
HOME=$PODMAN_TMPDIR/$HOME run_podman info

rm $new_home
}

@test "podman --root PATH --volumepath info - basic output" {
volumePath=${PODMAN_TMPDIR}/volumesGoHere
if ! is_remote; then
Expand Down

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