285 lines
11 KiB
Scheme
285 lines
11 KiB
Scheme
;;; GNU Guix --- Functional package management for GNU
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;;; Copyright © 2015, 2016, 2017, 2018 Ludovic Courtès <ludo@gnu.org>
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;;;
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;;; This file is part of GNU Guix.
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;;;
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;;; GNU Guix is free software; you can redistribute it and/or modify it
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;;; under the terms of the GNU General Public License as published by
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;;; the Free Software Foundation; either version 3 of the License, or (at
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;;; your option) any later version.
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;;;
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;;; GNU Guix is distributed in the hope that it will be useful, but
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;;; WITHOUT ANY WARRANTY; without even the implied warranty of
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;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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;;; GNU General Public License for more details.
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;;;
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;;; You should have received a copy of the GNU General Public License
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;;; along with GNU Guix. If not, see <http://www.gnu.org/licenses/>.
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(define-module (guix cve)
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#:use-module (guix utils)
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#:use-module (guix http-client)
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#:use-module (sxml ssax)
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#:use-module (web uri)
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#:use-module (srfi srfi-1)
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#:use-module (srfi srfi-9)
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#:use-module (srfi srfi-11)
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#:use-module (srfi srfi-19)
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#:use-module (srfi srfi-26)
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#:use-module (ice-9 match)
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#:use-module (ice-9 regex)
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#:use-module (ice-9 vlist)
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#:export (vulnerability?
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vulnerability-id
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vulnerability-packages
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xml->vulnerabilities
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current-vulnerabilities
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vulnerabilities->lookup-proc))
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;;; Commentary:
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;;;
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;;; This modules provides the tools to fetch, parse, and digest part of the
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;;; Common Vulnerabilities and Exposures (CVE) feeds provided by the US NIST
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;;; at <https://nvd.nist.gov/download.cfm#CVE_FEED>.
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;;;
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;;; Code:
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(define-record-type <vulnerability>
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(vulnerability id packages)
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vulnerability?
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(id vulnerability-id) ;string
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(packages vulnerability-packages)) ;((p1 v1 v2 v3) (p2 v1) ...)
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(define %now
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(current-date))
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(define %current-year
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(date-year %now))
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(define %past-year
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(- %current-year 1))
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(define (yearly-feed-uri year)
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"Return the URI for the CVE feed for YEAR."
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(string->uri
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(string-append "https://nvd.nist.gov/feeds/xml/cve/nvdcve-2.0-"
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(number->string year) ".xml.gz")))
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(define %current-year-ttl
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;; According to <https://nvd.nist.gov/download.cfm#CVE_FEED>, feeds are
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;; updated "approximately every two hours."
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(* 60 30))
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(define %past-year-ttl
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;; Update the previous year's database more and more infrequently.
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(* 3600 24 (date-month %now)))
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(define %cpe-package-rx
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;; For applications: "cpe:/a:VENDOR:PACKAGE:VERSION", or sometimes
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;; "cpe/a:VENDOR:PACKAGE:VERSION:PATCH-LEVEL".
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(make-regexp "^cpe:/a:([^:]+):([^:]+):([^:]+)((:.+)?)"))
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(define (cpe->package-name cpe)
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"Converts the Common Platform Enumeration (CPE) string CPE to a package
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name, in a very naive way. Return two values: the package name, and its
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version string. Return #f and #f if CPE does not look like an application CPE
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string."
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(cond ((regexp-exec %cpe-package-rx (string-trim-both cpe))
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=>
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(lambda (matches)
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(values (match:substring matches 2)
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(string-append (match:substring matches 3)
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(match (match:substring matches 4)
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("" "")
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(patch-level
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;; Drop the colon from things like
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;; "cpe:/a:openbsd:openssh:6.8:p1".
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(string-drop patch-level 1)))))))
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(else
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(values #f #f))))
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(define (cpe->product-alist products)
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"Given PRODUCTS, a list of CPE names, return the subset limited to the
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applications listed in PRODUCTS, with names converted to package names:
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(cpe->product-alist
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'(\"cpe:/a:gnu:libtasn1:4.7\" \"cpe:/a:gnu:libtasn1:4.6\" \"cpe:/a:gnu:cpio:2.11\"))
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=> ((\"libtasn1\" \"4.7\" \"4.6\") (\"cpio\" \"2.11\"))
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"
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(fold (lambda (product result)
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(let-values (((name version) (cpe->package-name product)))
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(if name
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(match result
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(((previous . versions) . tail)
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;; Attempt to coalesce NAME and PREVIOUS.
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(if (string=? name previous)
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(alist-cons name (cons version versions) tail)
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(alist-cons name (list version) result)))
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(()
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(alist-cons name (list version) result)))
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result)))
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'()
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(sort products string<?)))
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(define %parse-vulnerability-feed
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;; Parse the XML vulnerability feed from
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;; <https://nvd.nist.gov/download.cfm#CVE_FEED> and return a list of
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;; vulnerability objects.
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(ssax:make-parser NEW-LEVEL-SEED
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(lambda (elem-gi attributes namespaces expected-content
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seed)
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(match elem-gi
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((name-space . 'entry)
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(cons (assoc-ref attributes 'id) seed))
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((name-space . 'vulnerable-software-list)
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(cons '() seed))
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((name-space . 'product)
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(cons 'product seed))
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(x seed)))
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FINISH-ELEMENT
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(lambda (elem-gi attributes namespaces parent-seed
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seed)
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(match elem-gi
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((name-space . 'entry)
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(match seed
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(((? string? id) . rest)
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;; Some entries have no vulnerable-software-list.
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rest)
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((products id . rest)
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(match (cpe->product-alist products)
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(()
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;; No application among PRODUCTS.
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rest)
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(packages
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(cons (vulnerability id packages)
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rest))))))
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(x
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seed)))
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CHAR-DATA-HANDLER
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(lambda (str _ seed)
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(match seed
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(('product software-list . rest)
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;; Add STR to the vulnerable software list this
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;; <product> tag is part of.
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(cons (cons str software-list) rest))
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(x x)))))
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(define (xml->vulnerabilities port)
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"Read from PORT an XML feed of vulnerabilities and return a list of
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vulnerability objects."
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(reverse (%parse-vulnerability-feed port '())))
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(define vulnerability->sexp
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(match-lambda
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(($ <vulnerability> id packages)
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`(v ,id ,packages))))
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(define sexp->vulnerability
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(match-lambda
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(('v id (packages ...))
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(vulnerability id packages))))
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(define (write-cache input cache)
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"Read vulnerabilities as gzipped XML from INPUT, and write it as a compact
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sexp to CACHE."
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(call-with-decompressed-port 'gzip input
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(lambda (input)
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;; XXX: The SSAX "error port" is used to send pointless warnings such as
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;; "warning: Skipping PI". Turn that off.
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(define vulns
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(parameterize ((current-ssax-error-port (%make-void-port "w")))
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(xml->vulnerabilities input)))
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(write `(vulnerabilities
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1 ;format version
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,(map vulnerability->sexp vulns))
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cache))))
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(define (fetch-vulnerabilities year ttl)
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"Return the list of <vulnerability> for YEAR, assuming the on-disk cache has
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the given TTL (fetch from the NIST web site when TTL has expired)."
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(define (cache-miss uri)
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(format (current-error-port) "fetching CVE database for ~a...~%" year))
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(define (read* port)
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;; Disable read options to avoid populating the source property weak
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;; table, which speeds things up, saves memory, and works around
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;; <https://lists.gnu.org/archive/html/guile-devel/2017-09/msg00031.html>.
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(let ((options (read-options)))
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(dynamic-wind
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(lambda ()
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(read-disable 'positions))
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(lambda ()
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(read port))
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(lambda ()
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(read-options options)))))
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;; Note: We used to keep the original XML files in cache but parsing it
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;; would take typically ~15s for a year of data. Thus, we instead store a
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;; summarized version thereof as an sexp, which can be parsed in 1s or so.
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(let* ((port (http-fetch/cached (yearly-feed-uri year)
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#:ttl ttl
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#:write-cache write-cache
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#:cache-miss cache-miss))
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(sexp (read* port)))
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(close-port port)
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(match sexp
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(('vulnerabilities 1 vulns)
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(map sexp->vulnerability vulns)))))
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(define (current-vulnerabilities)
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"Return the current list of Common Vulnerabilities and Exposures (CVE) as
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published by the US NIST."
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(let ((past-years (unfold (cut > <> 3)
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(lambda (n)
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(- %current-year n))
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1+
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1))
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(past-ttls (unfold (cut > <> 3)
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(lambda (n)
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(* n %past-year-ttl))
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1+
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1)))
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(append-map fetch-vulnerabilities
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(cons %current-year past-years)
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(cons %current-year-ttl past-ttls))))
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(define (vulnerabilities->lookup-proc vulnerabilities)
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"Return a lookup procedure built from VULNERABILITIES that takes a package
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name and optionally a version number. When the version is omitted, the lookup
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procedure returns a list of vulnerabilities; otherwise, it returns a list of
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vulnerabilities affecting the given package version."
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(define table
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;; Map package names to lists of version/vulnerability pairs.
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(fold (lambda (vuln table)
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(match vuln
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(($ <vulnerability> id packages)
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(fold (lambda (package table)
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(match package
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((name . versions)
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(vhash-cons name (cons vuln versions)
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table))))
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table
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packages))))
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vlist-null
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vulnerabilities))
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(lambda* (package #:optional version)
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(vhash-fold* (if version
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(lambda (pair result)
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(match pair
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((vuln . versions)
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(if (member version versions)
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(cons vuln result)
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result))))
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(lambda (pair result)
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(match pair
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((vuln . _)
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(cons vuln result)))))
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'()
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package table)))
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;;; cve.scm ends here
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