cve-update-nvd2-native: Add an age threshold for incremental update

Add a new variable "CVE_DB_INCR_UPDATE_AGE_THRES", which can be used to
specify the maximum age of the database for doing an incremental update
For older databases, a full re-download is done.

With a value of "0", this forces a full-redownload.

(From OE-Core rev: 665c880ff8be1b18c2abe8fa878643dfa64b7d3d)

Signed-off-by: Yoann Congal <yoann.congal@smile.fr>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit 74c1765111b6610348eae4b7e41d7045ce58ef86)
Signed-off-by: Steve Sakoman <steve@sakoman.com>

meta/recipes-core/meta/cve-update-nvd2-native.bb

@@ -26,6 +26,12 @@ NVDCVE_API_KEY ?= ""
 # Use a negative value to skip the update
 CVE_DB_UPDATE_INTERVAL ?= "86400"
 
+# CVE database incremental update age threshold, in seconds. If the database is
+# older than this threshold, do a full re-download, else, do an incremental
+# update. By default: the maximum allowed value from NVD: 120 days (120*24*60*60)
+# Use 0 to force a full download.
+CVE_DB_INCR_UPDATE_AGE_THRES ?= "10368000"
+
 # Number of attempts for each http query to nvd server before giving up
 CVE_DB_UPDATE_ATTEMPTS ?= "5"
 
@@ -172,18 +178,24 @@ def update_db_file(db_tmp_file, d, database_time):
 
     req_args = {'startIndex' : 0}
 
-    # The maximum range for time is 120 days
-    # Force a complete update if our range is longer
-    if (database_time != 0):
+    incr_update_threshold = int(d.getVar("CVE_DB_INCR_UPDATE_AGE_THRES"))
+    if database_time != 0:
         database_date = datetime.datetime.fromtimestamp(database_time, tz=datetime.timezone.utc)
         today_date = datetime.datetime.now(tz=datetime.timezone.utc)
         delta = today_date - database_date
-        if delta.days < 120:
+        if incr_update_threshold == 0:
+            bb.note("CVE database: forced full update")
+        elif delta < datetime.timedelta(seconds=incr_update_threshold):
             bb.note("CVE database: performing partial update")
+            # The maximum range for time is 120 days
+            if delta > datetime.timedelta(days=120):
+                bb.error("CVE database: Trying to do an incremental update on a larger than supported range")
             req_args['lastModStartDate'] = database_date.isoformat()
             req_args['lastModEndDate'] = today_date.isoformat()
         else:
             bb.note("CVE database: file too old, forcing a full update")
+    else:
+        bb.note("CVE database: no preexisting database, do a full download")
 
     with bb.progress.ProgressHandler(d) as ph, open(os.path.join(d.getVar("TMPDIR"), 'cve_check'), 'a') as cve_f: