[pbs-devel] [PATCH proxmox-backup v2 1/2] fix #5439: allow to reuse existing datastore

[Gabriel Goller <g.goller@proxmox.com>]

Disallow creating datastores in non-empty directories. Allow adding
existing datastores via a 'reuse-datastore' checkmark. This only checks
if all the necessary directories (.chunks + subdirectories and .lock)
are existing and have the correct permissions, then opens the
datastore.

Signed-off-by: Gabriel Goller <g.goller@proxmox.com>
---

v2, thanks @Fabian:
 - also check on frontend for root 
 - forbid datastore creation if dir not empty
 - add reuse-datastore option
 - verify chunkstore directories permissions and owners

 pbs-datastore/src/chunk_store.rs | 49 ++++++++++++++++++++++++++++-
 src/api2/config/datastore.rs     | 54 +++++++++++++++++++++++++-------
 src/api2/node/disks/directory.rs |  1 +
 src/api2/node/disks/zfs.rs       |  1 +
 4 files changed, 93 insertions(+), 12 deletions(-)

diff --git a/pbs-datastore/src/chunk_store.rs b/pbs-datastore/src/chunk_store.rs
index 9f6289c9..077bc316 100644
--- a/pbs-datastore/src/chunk_store.rs
+++ b/pbs-datastore/src/chunk_store.rs
@@ -164,7 +164,7 @@ impl ChunkStore {
     /// Note that this must be used with care, as it's dangerous to create two instances on the
     /// same base path, as closing the underlying ProcessLocker drops all locks from this process
     /// on the lockfile (even if separate FDs)
-    pub(crate) fn open<P: Into<PathBuf>>(
+    pub fn open<P: Into<PathBuf>>(
         name: &str,
         base: P,
         sync_level: DatastoreFSyncLevel,
@@ -563,6 +563,53 @@ impl ChunkStore {
         // unwrap: only `None` in unit tests
         ProcessLocker::try_exclusive_lock(self.locker.clone().unwrap())
     }
+
+    /// Checks permissions and owner of passed path.
+    fn check_permissions<T: AsRef<Path>>(path: T, file_mode: u32) -> Result<(), Error> {
+        match nix::sys::stat::stat(path.as_ref()) {
+            Ok(stat) => {
+                if stat.st_uid != u32::from(pbs_config::backup_user()?.uid)
+                    || stat.st_gid != u32::from(pbs_config::backup_group()?.gid)
+                    || stat.st_mode & 0o700 != file_mode
+                {
+                    bail!(
+                            "unable to open existing chunk store path {:?} - permissions or owner not correct",
+                            path.as_ref(),
+                        );
+                }
+            }
+            Err(err) => {
+                bail!(
+                    "unable to open existing chunk store path {:?} - {err}",
+                    path.as_ref(),
+                );
+            }
+        }
+        Ok(())
+    }
+
+    /// Verify vital files in datastore. Checks the owner and permissions of: the chunkstore, it's
+    /// subdirectories and the lock file.
+    pub fn verify_chunkstore<T: AsRef<Path>>(path: T) -> Result<(), Error> {
+        // Check datastore root path perm/owner
+        ChunkStore::check_permissions(path.as_ref(), 0o700)?;
+
+        let chunk_dir = Self::chunk_dir(path.as_ref());
+        // Check datastore .chunks path perm/owner
+        ChunkStore::check_permissions(&chunk_dir, 0o700)?;
+
+        // Check all .chunks subdirectories
+        for i in 0..64 * 1024 {
+            let mut l1path = chunk_dir.clone();
+            l1path.push(format!("{:04x}", i));
+            ChunkStore::check_permissions(&l1path, 0o700)?;
+        }
+
+        // Check .lock file
+        let lockfile_path = Self::lockfile_path(path.as_ref());
+        ChunkStore::check_permissions(lockfile_path, 0o600)?;
+        Ok(())
+    }
 }
 
 #[test]
diff --git a/src/api2/config/datastore.rs b/src/api2/config/datastore.rs
index 6b742acb..f1e80b2d 100644
--- a/src/api2/config/datastore.rs
+++ b/src/api2/config/datastore.rs
@@ -1,7 +1,7 @@
 use std::path::PathBuf;
 
 use ::serde::{Deserialize, Serialize};
-use anyhow::Error;
+use anyhow::{bail, Error};
 use hex::FromHex;
 use serde_json::Value;
 
@@ -70,23 +70,48 @@ pub(crate) fn do_create_datastore(
     _lock: BackupLockGuard,
     mut config: SectionConfigData,
     datastore: DataStoreConfig,
+    reuse_datastore: bool,
     worker: Option<&dyn WorkerTaskContext>,
 ) -> Result<(), Error> {
     let path: PathBuf = datastore.path.clone().into();
 
+    if path.parent().is_none() {
+        bail!("cannot create datastore in root path");
+    }
+
+    let datastore_empty = std::fs::read_dir(path.clone())?.all(|dir| {
+        dir.map_or(false, |file| {
+            file.file_name().to_str().map_or(false, |name| {
+                (name.starts_with('.')
+                    && !(name == ".chunks" || name == ".lock" || name == ".gc-status"))
+                    || name.starts_with("lost+found")
+            })
+        })
+    });
+
     let tuning: DatastoreTuning = serde_json::from_value(
         DatastoreTuning::API_SCHEMA
             .parse_property_string(datastore.tuning.as_deref().unwrap_or(""))?,
     )?;
-    let backup_user = pbs_config::backup_user()?;
-    let _store = ChunkStore::create(
-        &datastore.name,
-        path,
-        backup_user.uid,
-        backup_user.gid,
-        worker,
-        tuning.sync_level.unwrap_or_default(),
-    )?;
+
+    if !datastore_empty && !reuse_datastore {
+        bail!("Directory is not empty!");
+    } else if !datastore_empty && reuse_datastore {
+        ChunkStore::verify_chunkstore(&path)?;
+
+        let _store =
+            ChunkStore::open(&datastore.name, path, tuning.sync_level.unwrap_or_default())?;
+    } else {
+        let backup_user = pbs_config::backup_user()?;
+        let _store = ChunkStore::create(
+            &datastore.name,
+            path,
+            backup_user.uid,
+            backup_user.gid,
+            worker,
+            tuning.sync_level.unwrap_or_default(),
+        )?;
+    }
 
     config.set_data(&datastore.name, "datastore", &datastore)?;
 
@@ -103,6 +128,12 @@ pub(crate) fn do_create_datastore(
                 type: DataStoreConfig,
                 flatten: true,
             },
+            "reuse-datastore": {
+                type: Boolean,
+                optional: true,
+                default: false,
+                description: "Re-use existing datastore directory."
+            }
         },
     },
     access: {
@@ -112,6 +143,7 @@ pub(crate) fn do_create_datastore(
 /// Create new datastore config.
 pub fn create_datastore(
     config: DataStoreConfig,
+    reuse_datastore: bool,
     rpcenv: &mut dyn RpcEnvironment,
 ) -> Result<String, Error> {
     let lock = pbs_config::datastore::lock_config()?;
@@ -156,7 +188,7 @@ pub fn create_datastore(
         auth_id.to_string(),
         to_stdout,
         move |worker| {
-            do_create_datastore(lock, section_config, config, Some(&worker))?;
+            do_create_datastore(lock, section_config, config, reuse_datastore, Some(&worker))?;
 
             if let Some(prune_job_config) = prune_job_config {
                 do_create_prune_job(prune_job_config, Some(&worker))
diff --git a/src/api2/node/disks/directory.rs b/src/api2/node/disks/directory.rs
index 9f1112a9..25cfe784 100644
--- a/src/api2/node/disks/directory.rs
+++ b/src/api2/node/disks/directory.rs
@@ -217,6 +217,7 @@ pub fn create_datastore_disk(
                     lock,
                     config,
                     datastore,
+                    false,
                     Some(&worker),
                 )?;
             }
diff --git a/src/api2/node/disks/zfs.rs b/src/api2/node/disks/zfs.rs
index 673dc1bf..ad2129fc 100644
--- a/src/api2/node/disks/zfs.rs
+++ b/src/api2/node/disks/zfs.rs
@@ -323,6 +323,7 @@ pub fn create_zpool(
                     lock,
                     config,
                     datastore,
+                    false,
                     Some(&worker),
                 )?;
             }
-- 
2.43.0



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