tape: use specialized encryption key per media-set

src/api2/tape/drive.rs

@@ -1053,7 +1053,9 @@ pub fn catalog_media(
                         MediaCatalog::destroy(status_path, &media_id.label.uuid)?;
                         return Ok(());
                     }
-                    let encrypt_fingerprint = set.encryption_key_fingerprint.clone();
+                    let encrypt_fingerprint = set.encryption_key_fingerprint.clone()
+                        .map(|fp| (fp, set.uuid.clone()));
+
                     drive.set_encryption(encrypt_fingerprint)?;
 
                     set.pool.clone()

src/bin/sg-tape-cmd.rs

@@ -17,6 +17,7 @@ use proxmox::{
         cli::*,
         RpcEnvironment,
     },
+    tools::Uuid,
 };
 
 use proxmox_backup::{
@@ -26,6 +27,7 @@ use proxmox_backup::{
         LINUX_DRIVE_PATH_SCHEMA,
         DRIVE_NAME_SCHEMA,
         TAPE_ENCRYPTION_KEY_FINGERPRINT_SCHEMA,
+        MEDIA_SET_UUID_SCHEMA,
         LinuxTapeDrive,
     },
     tape::{
@@ -193,6 +195,10 @@ fn tape_alert_flags(
                 schema: TAPE_ENCRYPTION_KEY_FINGERPRINT_SCHEMA,
                 optional: true,
             },
+            uuid: {
+                schema: MEDIA_SET_UUID_SCHEMA,
+                optional: true,
+            },
             drive: {
                 schema: DRIVE_NAME_SCHEMA,
                 optional: true,
@@ -212,13 +218,25 @@ fn tape_alert_flags(
 /// Set or clear encryption key
 fn set_encryption(
     fingerprint: Option<Fingerprint>,
+    uuid: Option<Uuid>,
     param: Value,
 ) -> Result<(), Error> {
 
     let result = proxmox::try_block!({
         let mut handle = get_tape_handle(&param)?;
 
-        handle.set_encryption(fingerprint)?;
+        match (fingerprint, uuid) {
+            (Some(fingerprint), Some(uuid)) => {
+                handle.set_encryption(Some((fingerprint, uuid)))?;
+            }
+            (Some(_), None) => {
+                bail!("missing media set uuid");
+            }
+            (None, _) => {
+                handle.set_encryption(None)?;
+            }
+        }
+
         Ok(())
     }).map_err(|err: Error| err.to_string());
 

src/tape/drive/linux_tape.rs

@@ -7,6 +7,7 @@ use anyhow::{bail, format_err, Error};
 use nix::fcntl::{fcntl, FcntlArg, OFlag};
 
 use proxmox::sys::error::SysResult;
+use proxmox::tools::Uuid;
 
 use crate::{
     config,
@@ -535,16 +536,33 @@ impl TapeDriver for LinuxTapeHandle {
     /// Note: Only 'root' user may run RAW SG commands, so we need to
     /// spawn setuid binary 'sg-tape-cmd'. Also, encryption key file
     /// is only readable by root.
-    fn set_encryption(&mut self, key_fingerprint: Option<Fingerprint>) -> Result<(), Error> {
+    fn set_encryption(
+        &mut self,
+        key_fingerprint: Option<(Fingerprint, Uuid)>,
+    ) -> Result<(), Error> {
 
         if nix::unistd::Uid::effective().is_root() {
 
-            if let Some(ref key_fingerprint) = key_fingerprint {
+            if let Some((ref key_fingerprint, ref uuid)) = key_fingerprint {
 
                 let (key_map, _digest) = config::tape_encryption_keys::load_keys()?;
                 match key_map.get(key_fingerprint) {
                     Some(item) => {
-                        return set_encryption(&mut self.file, Some(item.key));
+
+                        // derive specialized key for each media-set
+
+                        let mut tape_key = [0u8; 32];
+
+                        let uuid_bytes: [u8; 16] = uuid.as_bytes().clone();
+
+                        openssl::pkcs5::pbkdf2_hmac(
+                            &item.key,
+                            &uuid_bytes,
+                            10,
+                            openssl::hash::MessageDigest::sha256(),
+                            &mut tape_key)?;
+
+                        return set_encryption(&mut self.file, Some(tape_key));
                     }
                     None => bail!("unknown tape encryption key '{}'", key_fingerprint),
                 }
@@ -556,9 +574,10 @@ impl TapeDriver for LinuxTapeHandle {
         let mut command = std::process::Command::new(
             "/usr/lib/x86_64-linux-gnu/proxmox-backup/sg-tape-cmd");
         command.args(&["encryption"]);
-        if let Some(fingerprint) = key_fingerprint {
+        if let Some((fingerprint, uuid)) = key_fingerprint {
             let fingerprint = crate::tools::format::as_fingerprint(fingerprint.bytes());
             command.args(&["--fingerprint", &fingerprint]);
+            command.args(&["--uuid", &uuid.to_string()]);
         }
         command.args(&["--stdin"]);
         command.stdin(unsafe { std::process::Stdio::from_raw_fd(self.file.as_raw_fd())});

src/tape/drive/mod.rs

@@ -22,8 +22,13 @@ use anyhow::{bail, format_err, Error};
 use ::serde::{Deserialize};
 use serde_json::Value;
 
-use proxmox::tools::io::ReadExt;
-use proxmox::api::section_config::SectionConfigData;
+use proxmox::{
+    tools::{
+        Uuid,
+        io::ReadExt,
+    },
+    api::section_config::SectionConfigData,
+};
 
 use crate::{
     backup::{
@@ -190,7 +195,14 @@ pub trait TapeDriver {
     }
 
     /// Set or clear encryption key
-    fn set_encryption(&mut self, key_fingerprint: Option<Fingerprint>) -> Result<(), Error> {
+    ///
+    /// We use the media_set_uuid to XOR the secret key with the
+    /// uuid (first 16 bytes), so that each media set uses an uique
+    /// key for encryption.
+    fn set_encryption(
+        &mut self,
+        key_fingerprint: Option<(Fingerprint, Uuid)>,
+    ) -> Result<(), Error> {
         if key_fingerprint.is_some() {
             bail!("drive does not support encryption");
         }

src/tape/pool_writer.rs

@@ -231,12 +231,12 @@ impl PoolWriter {
             media.id(),
         )?;
 
-        let encrypt_fingerprint = media
-            .media_set_label()
-            .as_ref()
-            .unwrap()
+        let media_set = media.media_set_label().clone().unwrap();
+
+        let encrypt_fingerprint = media_set
             .encryption_key_fingerprint
-            .clone();
+            .clone()
+            .map(|fp| (fp, media_set.uuid.clone()));
 
         drive.set_encryption(encrypt_fingerprint)?;