feat: Add offline command line option (#1452)

README.md

@@ -29,6 +29,7 @@ Usage:
       -V, --version         show program's version number and exit
       --disable-version-check
                             skips checking for a new version
+      --offline             operate in offline mode							
 
     CVE Data Download:
       -n {json,api}, --nvd {json,api}
@@ -118,6 +119,8 @@ in the terminal and provide it as an input by running `cve-bin-tool -L pkg-list`
 You can use `--config` option to provide configuration file for the tool. You can still override options specified in config file with command line arguments. See our sample config files in the
 [test/config](https://github.com/intel/cve-bin-tool/blob/main/test/config/)
 
+Specifying the `--offline` option when running a scan ensures that cve-bin-tool doesn't attempt to download the latest database files or to check for a newer version of the tool.
+
 The 0.3.1 release is intended to be the last release to officially support
 python 2.7; please switch to python 3.6+ for future releases and to use the
 development tree. You can check [our CI configuration](https://github.com/intel/cve-bin-tool/blob/main/.github/workflows/pythonapp.yml) to see what versions of python we're explicitly testing.

cve_bin_tool/cli.py

@@ -19,6 +19,7 @@
 import platform
 import sys
 import textwrap
+import time
 from collections import ChainMap
 from typing import Dict
 
@@ -219,6 +220,11 @@ def main(argv=None):
         action="store_true",
         help="skips checking for a new version",
     )
+    parser.add_argument(
+        "--offline",
+        action="store_true",
+        help="operate in offline mode",
+    )
 
     merge_report_group = parser.add_argument_group(
         "Merge Report", "Arguments related to Intermediate and Merged Reports"
@@ -303,6 +309,7 @@ def main(argv=None):
         "affected_versions": 0,
         "sbom": "spdx",
         "sbom_file": "",
+        "offline": False,
     }
 
     with ErrorHandler(mode=ErrorMode.NoTrace):
@@ -349,6 +356,15 @@ def main(argv=None):
     if int(args["cvss"]) > 0:
         score = int(args["cvss"])
 
+    # Offline processing
+    if args["offline"]:
+        # Override version check and database update arguments
+        version_check = True
+        db_update = "never"
+    else:
+        version_check = args["disable_version_check"]
+        db_update = args["update"]
+
     # Check for PDF support
     output_format = args["format"]
     if output_format == "pdf" and importlib.util.find_spec("reportlab") is None:
@@ -380,12 +396,10 @@ def main(argv=None):
     # Database update related settings
     # Connect to the database
     cvedb_orig = CVEDB(
-        version_check=not args["disable_version_check"],
+        version_check=not version_check,
         error_mode=error_mode,
         nvd_type=args["nvd"],
-        incremental_update=True
-        if args["update"] == "latest" and args["nvd"]
-        else False,
+        incremental_update=True if db_update == "latest" and args["nvd"] else False,
     )
 
     # if OLD_CACHE_DIR (from cvedb.py) exists, print warning
@@ -394,15 +408,23 @@ def main(argv=None):
             f"Obsolete cache dir {OLD_CACHE_DIR} is no longer needed and can be removed."
         )
 
+    # Check database exists if operating in offline mode.
+    if args["offline"] and not cvedb_orig.check_db_exists():
+        LOGGER.critical("Database does not exist.")
+        LOGGER.info(
+            "Consult the documentation at https://cve-bin-tool.readthedocs.io/en/latest/how_to_guides/offline.html to find out how to setup offline operation."
+        )
+        return -1
+
     # Clear data if -u now is set
-    if args["update"] == "now":
+    if db_update == "now":
         cvedb_orig.clear_cached_data()
 
-    if args["update"] == "latest":
+    if db_update == "latest":
         cvedb_orig.refresh_cache_and_update_db()
 
     # update db if needed
-    if args["update"] != "never":
+    if db_update != "never":
         cvedb_orig.get_cvelist_if_stale()
     else:
         if args["nvd"] == "json":
@@ -417,6 +439,12 @@ def main(argv=None):
         with ErrorHandler(mode=error_mode, logger=LOGGER):
             raise CVEDataMissing("No data in CVE Database")
 
+    # Report time of last database update
+    db_date = time.strftime(
+        "%d %B %Y at %H:%M:%S", time.localtime(cvedb_orig.get_db_update_date())
+    )
+    LOGGER.info(f"CVE database last updated on {db_date}")
+
     cvedb_orig.remove_cache_backup()
 
     # Input validation

cve_bin_tool/cvedb.py

@@ -122,6 +122,9 @@ async def nist_fetch_using_api(self):
         nvd_api.session = None
         return nvd_api.all_cve_entries
 
+    def check_db_exists(self):
+        return os.path.isfile(self.dbpath)
+
     def get_db_update_date(self):
         # last time when CVE data was updated
         self.time_of_last_update = datetime.datetime.fromtimestamp(

doc/how_to_guides/offline.md

@@ -15,12 +15,15 @@ NOTE The tool will error with InsufficientArgs because no directory was specifie
 The way of transfer depends on the environment. The files to be transferred are in "~/.cache/cve-bin-tool"
 
 ## Import the vulnerability database file on the offline system
-The vulnerability database should be copied into ~/.cache/cve-bin-tool
+The vulnerability database should be copied into ~/.cache/cve-bin-tool.
 
-## Run cve-bin-tool with --update never  and --disable-version-check options
-In an offline environment, when running a scan specify `--update never` so that cve-bin-tool doesn't attempt to download the latest database files and `--disable-version-check` so that the cve-bin-tool doesn't attempt to check for a newer version of the tool.
+The cve-bin-tool will fail to operate in offline mode if a vulnerability database is not present on the system.
+
+## Run cve-bin-tool with --offline option
+In an offline environment, specify the `--offline` option when running a scan so that cve-bin-tool doesn't attempt to download the latest database files or check for a newer version of the tool.
+The `--offline` option is equivalent to specifying `--update never` and `--disable-version-check` options.
 
 ## Maintenance Updates
-In an offline environment, it is important to update the vulnerability database on a regular basis as often as you feel appropriate, so that the scanner can continue to detect recently-identified vulnerabilities. If any changes to CVE data is required (e.g. to remove false positives), you might also want to create and copy over a triage data file for usage.
+In an offline environment, it is important to update the vulnerability database on a regular basis as often as you feel appropriate, so that the scanner can continue to detect recently-identified vulnerabilities. If any changes to CVE data is required (e.g. to remove false positives), you might also want to create and copy over a triage data file for usage. The time of the latest database update is reported whenever a scan is performed.
 
 It is important to periodically check if the cve-bin-tool has also been updated as this check cannot be performed within an offline environment.