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;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2015, 2016 Ludovic Courtès <ludo@gnu.org>
;;;
;;; This file is part of GNU Guix.
;;;
;;; GNU Guix is free software; you can redistribute it and/or modify it
;;; under the terms of the GNU General Public License as published by
;;; the Free Software Foundation; either version 3 of the License, or (at
;;; your option) any later version.
;;;
;;; GNU Guix is distributed in the hope that it will be useful, but
;;; WITHOUT ANY WARRANTY; without even the implied warranty of
;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;;; GNU General Public License for more details.
;;;
;;; You should have received a copy of the GNU General Public License
;;; along with GNU Guix. If not, see <http://www.gnu.org/licenses/>.
(define-module (guix cve)
#:use-module (guix utils)
#:use-module (guix http-client)
#:use-module (sxml ssax)
#:use-module (web uri)
#:use-module (srfi srfi-1)
#:use-module (srfi srfi-9)
#:use-module (srfi srfi-19)
#:use-module (ice-9 match)
#:use-module (ice-9 regex)
#:use-module (ice-9 vlist)
#:export (vulnerability?
vulnerability-id
vulnerability-packages
xml->vulnerabilities
current-vulnerabilities
vulnerabilities->lookup-proc))
;;; Commentary:
;;;
;;; This modules provides the tools to fetch, parse, and digest part of the
;;; Common Vulnerabilities and Exposures (CVE) feeds provided by the US NIST
;;; at <https://nvd.nist.gov/download.cfm#CVE_FEED>.
;;;
;;; Code:
(define-record-type <vulnerability>
(vulnerability id packages)
vulnerability?
(id vulnerability-id)
(packages vulnerability-packages))
(define %now
(current-date))
(define %current-year
(date-year %now))
(define %past-year
(- %current-year 1))
(define (yearly-feed-uri year)
"Return the URI for the CVE feed for YEAR."
(string->uri
(string-append "https://static.nvd.nist.gov/feeds/xml/cve/nvdcve-2.0-"
(number->string year) ".xml.gz")))
(define %current-year-ttl
;; According to <https://nvd.nist.gov/download.cfm#CVE_FEED>, feeds are
;; updated "approximately every two hours."
(* 3600 3))
(define %past-year-ttl
;; Update the previous year's database more and more infrequently.
(* 3600 24 2 (date-month %now)))
(define (call-with-cve-port uri ttl proc)
"Pass PROC an input port from which to read the CVE stream."
(let ((port (http-fetch/cached uri #:ttl ttl)))
(dynamic-wind
(const #t)
(lambda ()
(call-with-decompressed-port 'gzip port
(lambda (port)
(setvbuf port _IOFBF 65536)
(proc port))))
(lambda ()
(close-port port)))))
(define %cpe-package-rx
;; For applications: "cpe:/a:VENDOR:PACKAGE:VERSION", or sometimes
;; "cpe/a:VENDOR:PACKAGE:VERSION:PATCH-LEVEL".
(make-regexp "^cpe:/a:([^:]+):([^:]+):([^:]+)((:.+)?)"))
(define (cpe->package-name cpe)
"Converts the Common Platform Enumeration (CPE) string CPE to a package
name, in a very naive way. Return #f if CPE does not look like an application
CPE string."
(and=> (regexp-exec %cpe-package-rx (string-trim-both cpe))
(lambda (matches)
(cons (match:substring matches 2)
(string-append (match:substring matches 3)
(match (match:substring matches 4)
("" "")
(patch-level
;; Drop the colon from things like
;; "cpe:/a:openbsd:openssh:6.8:p1".
(string-drop patch-level 1))))))))
(define %parse-vulnerability-feed
;; Parse the XML vulnerability feed from
;; <https://nvd.nist.gov/download.cfm#CVE_FEED> and return a list of
;; vulnerability objects.
(ssax:make-parser NEW-LEVEL-SEED
(lambda (elem-gi attributes namespaces expected-content
seed)
(match elem-gi
((name-space . 'entry)
(cons (assoc-ref attributes 'id) seed))
((name-space . 'vulnerable-software-list)
(cons '() seed))
((name-space . 'product)
(cons 'product seed))
(x seed)))
FINISH-ELEMENT
(lambda (elem-gi attributes namespaces parent-seed
seed)
(match elem-gi
((name-space . 'entry)
(match seed
(((? string? id) . rest)
;; Some entries have no vulnerable-software-list.
rest)
((products id . rest)
(match (filter-map cpe->package-name products)
(()
;; No application among PRODUCTS.
rest)
(packages
(cons (vulnerability id (reverse packages))
rest))))))
(x
seed)))
CHAR-DATA-HANDLER
(lambda (str _ seed)
(match seed
(('product software-list . rest)
;; Add STR to the vulnerable software list this
;; <product> tag is part of.
(cons (cons str software-list) rest))
(x x)))))
(define (xml->vulnerabilities port)
"Read from PORT an XML feed of vulnerabilities and return a list of
vulnerability objects."
(reverse (%parse-vulnerability-feed port '())))
(define (current-vulnerabilities)
"Return the current list of Common Vulnerabilities and Exposures (CVE) as
published by the US NIST."
(define (read-vulnerabilities uri ttl)
(call-with-cve-port uri ttl
(lambda (port)
;; XXX: The SSAX "error port" is used to send pointless warnings such as
;; "warning: Skipping PI". Turn that off.
(parameterize ((current-ssax-error-port (%make-void-port "w")))
(xml->vulnerabilities port)))))
(append-map read-vulnerabilities
(list (yearly-feed-uri %past-year)
(yearly-feed-uri %current-year))
(list %past-year-ttl
%current-year-ttl)))
(define (vulnerabilities->lookup-proc vulnerabilities)
"Return a lookup procedure built from VULNERABILITIES that takes a package
name and optionally a version number. When the version is omitted, the lookup
procedure returns a list of version/vulnerability pairs; otherwise, it returns
a list of vulnerabilities affection the given package version."
(define table
;; Map package names to lists of version/vulnerability pairs.
(fold (lambda (vuln table)
(match vuln
(($ <vulnerability> id packages)
(fold (lambda (package table)
(match package
((name . version)
(vhash-cons name (cons version vuln)
table))))
table
packages))))
vlist-null
vulnerabilities))
(lambda* (package #:optional version)
(vhash-fold* (if version
(lambda (pair result)
(match pair
((v . vuln)
(if (string=? v version)
(cons vuln result)
result))))
cons)
'()
package table)))
;;; Local Variables:
;;; eval: (put 'call-with-cve-port 'scheme-indent-function 2)
;;; End:
;;; cve.scm ends here
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