cve-update-db-native: avoid incomplete updates

The database update has been done on the original file. In case of
network connection issues, temporary outage of the NVD server or
a similar situation, the function could exit with incomplete data
in the database. This patch solves the issue by performing the update
on a copy of the database. It replaces the main one only if the whole
update was successful.

See https://bugzilla.yoctoproject.org/show_bug.cgi?id=14929

Reported-by: Alberto Pianon <alberto@pianon.eu>
(From OE-Core rev: 8efe99214d8b005f0ecac690ce5ba17b31758f92)

Signed-off-by: Marta Rybczynska <marta.rybczynska@linaro.org>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-core/meta/cve-update-db-native.bb

@@ -21,6 +21,8 @@ CVE_DB_UPDATE_INTERVAL ?= "86400"
 # Timeout for blocking socket operations, such as the connection attempt.
 CVE_SOCKET_TIMEOUT ?= "60"
 
+CVE_DB_TEMP_FILE ?= "${CVE_CHECK_DB_DIR}/temp_nvdcve_1.1.db"
+
 python () {
     if not bb.data.inherits_class("cve-check", d):
         raise bb.parse.SkipRecipe("Skip recipe when cve-check class is not loaded.")
@@ -32,25 +34,15 @@ python do_fetch() {
     """
     import bb.utils
     import bb.progress
-    import sqlite3, urllib, urllib.parse, gzip
-    from datetime import date
+    import shutil
 
     bb.utils.export_proxies(d)
 
-    YEAR_START = 2002
-
     db_file = d.getVar("CVE_CHECK_DB_FILE")
     db_dir = os.path.dirname(db_file)
+    db_tmp_file = d.getVar("CVE_DB_TEMP_FILE")
 
-    cve_socket_timeout = int(d.getVar("CVE_SOCKET_TIMEOUT"))
-
-    if os.path.exists("{0}-journal".format(db_file)):
-        # If a journal is present the last update might have been interrupted. In that case,
-        # just wipe any leftovers and force the DB to be recreated.
-        os.remove("{0}-journal".format(db_file))
-
-        if os.path.exists(db_file):
-            os.remove(db_file)
+    cleanup_db_download(db_file, db_tmp_file)
 
     # The NVD database changes once a day, so no need to update more frequently
     # Allow the user to force-update
@@ -68,9 +60,60 @@ python do_fetch() {
         pass
 
     bb.utils.mkdirhier(db_dir)
+    if os.path.exists(db_file):
+        shutil.copy2(db_file, db_tmp_file)
+
+    if update_db_file(db_tmp_file, d) == True:
+        # Update downloaded correctly, can swap files
+        shutil.move(db_tmp_file, db_file)
+    else:
+        # Update failed, do not modify the database
+        bb.note("CVE database update failed")
+        os.remove(db_tmp_file)
+}
+
+do_fetch[lockfiles] += "${CVE_CHECK_DB_FILE_LOCK}"
+do_fetch[file-checksums] = ""
+do_fetch[vardeps] = ""
+
+def cleanup_db_download(db_file, db_tmp_file):
+    """
+    Cleanup the download space from possible failed downloads
+    """
+
+    # Clean up the updates done on the main file
+    # Remove it only if a journal file exists - it means a complete re-download
+    if os.path.exists("{0}-journal".format(db_file)):
+        # If a journal is present the last update might have been interrupted. In that case,
+        # just wipe any leftovers and force the DB to be recreated.
+        os.remove("{0}-journal".format(db_file))
+
+        if os.path.exists(db_file):
+            os.remove(db_file)
+
+    # Clean-up the temporary file downloads, we can remove both journal
+    # and the temporary database
+    if os.path.exists("{0}-journal".format(db_tmp_file)):
+        # If a journal is present the last update might have been interrupted. In that case,
+        # just wipe any leftovers and force the DB to be recreated.
+        os.remove("{0}-journal".format(db_tmp_file))
+
+    if os.path.exists(db_tmp_file):
+        os.remove(db_tmp_file)
+
+def update_db_file(db_tmp_file, d):
+    """
+    Update the given database file
+    """
+    import bb.utils, bb.progress
+    from datetime import date
+    import urllib, gzip, sqlite3
+
+    YEAR_START = 2002
+    cve_socket_timeout = int(d.getVar("CVE_SOCKET_TIMEOUT"))
 
     # Connect to database
-    conn = sqlite3.connect(db_file)
+    conn = sqlite3.connect(db_tmp_file)
     initialize_db(conn)
 
     with bb.progress.ProgressHandler(d) as ph, open(os.path.join(d.getVar("TMPDIR"), 'cve_check'), 'a') as cve_f:
@@ -88,7 +131,7 @@ python do_fetch() {
             except urllib.error.URLError as e:
                 cve_f.write('Warning: CVE db update error, Unable to fetch CVE data.\n\n')
                 bb.warn("Failed to fetch CVE data (%s)" % e.reason)
-                return
+                return False
 
             if response:
                 for l in response.read().decode("utf-8").splitlines():
@@ -98,7 +141,7 @@ python do_fetch() {
                         break
                 else:
                     bb.warn("Cannot parse CVE metadata, update failed")
-                    return
+                    return False
 
             # Compare with current db last modified date
             cursor = conn.execute("select DATE from META where YEAR = ?", (year,))
@@ -119,7 +162,7 @@ python do_fetch() {
                 except urllib.error.URLError as e:
                     cve_f.write('Warning: CVE db update error, CVE data is outdated.\n\n')
                     bb.warn("Cannot parse CVE data (%s), update failed" % e.reason)
-                    return
+                    return False
             else:
                 bb.debug(2, "Already up to date (last modified %s)" % last_modified)
             # Update success, set the date to cve_check file.
@@ -128,11 +171,7 @@ python do_fetch() {
 
         conn.commit()
         conn.close()
-}
-
-do_fetch[lockfiles] += "${CVE_CHECK_DB_FILE_LOCK}"
-do_fetch[file-checksums] = ""
-do_fetch[vardeps] = ""
+        return True
 
 def initialize_db(conn):
     with conn: