;;; GNU Guix --- Functional package management for GNU ;;; Copyright © 2015, 2016, 2017, 2018, 2019, 2020, 2021 Ludovic Courtès ;;; ;;; 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 . (define-module (guix cve) #:use-module (guix utils) #:use-module (guix http-client) #:use-module (guix i18n) #:use-module ((guix diagnostics) #:select (formatted-message)) #:use-module (json) #:use-module (web uri) #:use-module (srfi srfi-1) #:use-module (srfi srfi-9) #:use-module (srfi srfi-19) #:use-module (srfi srfi-26) #:use-module (srfi srfi-34) #:use-module (srfi srfi-35) #:use-module (srfi srfi-71) #:use-module (ice-9 match) #:use-module (ice-9 regex) #:use-module (ice-9 vlist) #:export (json->cve-items cve-item? cve-item-cve cve-item-configurations cve-item-published-date cve-item-last-modified-date cve? cve-id cve-data-type cve-data-format cve-references cve-reference? cve-reference-url cve-reference-tags vulnerability? vulnerability-id vulnerability-packages json->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 . ;;; ;;; Code: (define (string->date* str) (string->date str "~Y-~m-~dT~H:~M~z")) (define-json-mapping cve-item cve-item? json->cve-item (cve cve-item-cve "cve" json->cve) ; (configurations cve-item-configurations ;list of sexps "configurations" configuration-data->cve-configurations) (published-date cve-item-published-date "publishedDate" string->date*) (last-modified-date cve-item-last-modified-date "lastModifiedDate" string->date*)) (define-json-mapping cve cve? json->cve (id cve-id "CVE_data_meta" ;string (cut assoc-ref <> "ID")) (data-type cve-data-type ;'CVE "data_type" string->symbol) (data-format cve-data-format ;'MITRE "data_format" string->symbol) (references cve-references ;list of "references" reference-data->cve-references)) (define-json-mapping cve-reference cve-reference? json->cve-reference (url cve-reference-url) ;string (tags cve-reference-tags ;list of strings "tags" vector->list)) (define (reference-data->cve-references alist) (map json->cve-reference ;; Normally "reference_data" is always present but rejected CVEs such ;; as CVE-2020-10020 can lack it. (vector->list (or (assoc-ref alist "reference_data") '#())))) (define %cpe-package-rx ;; For applications: "cpe:2.3:a:VENDOR:PACKAGE:VERSION", or sometimes ;; "cpe:2.3:a:VENDOR:PACKAGE:VERSION:PATCH-LEVEL". (make-regexp "^cpe:2\\.3:a:([^:]+):([^:]+):([^:]+):([^:]+):")) (define (cpe->package-identifier cpe) "Converts the Common Platform Enumeration (CPE) string CPE to a package identifier, in a very naive way. Return three values: the CPE vendor, the package name, and its version string. Return three #f values if CPE does not look like an application CPE string." (cond ((regexp-exec %cpe-package-rx cpe) => (lambda (matches) (values (match:substring matches 1) (match:substring matches 2) (match (match:substring matches 3) ("*" '_) (version (string-append version (match (match:substring matches 4) ("" "") (patch-level ;; Drop the colon from things like ;; "cpe:2.3:a:openbsd:openssh:6.8:p1". (string-drop patch-level 1))))))))) (else (values #f #f #f)))) (define (cpe-match->cve-configuration alist) "Convert ALIST, a \"cpe_match\" alist, into an sexp representing the package and versions matched. Return #f if ALIST doesn't correspond to an application package." (let ((cpe (assoc-ref alist "cpe23Uri")) (starti (assoc-ref alist "versionStartIncluding")) (starte (assoc-ref alist "versionStartExcluding")) (endi (assoc-ref alist "versionEndIncluding")) (ende (assoc-ref alist "versionEndExcluding"))) ;; Normally "cpe23Uri" is here in each "cpe_match" item, but CVE-2020-0534 ;; has a configuration that lacks it. (and cpe (let ((vendor package version (cpe->package-identifier cpe))) (and package `(,vendor ,package ,(cond ((and (or starti starte) (or endi ende)) `(and ,(if starti `(>= ,starti) `(> ,starte)) ,(if endi `(<= ,endi) `(< ,ende)))) (starti `(>= ,starti)) (starte `(> ,starte)) (endi `(<= ,endi)) (ende `(< ,ende)) (else version)))))))) (define (configuration-data->cve-configurations alist) "Given ALIST, a JSON dictionary for the baroque \"configurations\" element found in CVEs, return an sexp such as (\"binutils\" (< \"2.31\")) that represents matching configurations." (define string->operator (match-lambda ("OR" 'or) ("AND" 'and))) (define (node->configuration node) (let ((operator (string->operator (assoc-ref node "operator")))) (cond ((assoc-ref node "cpe_match") => (lambda (matches) (let ((matches (vector->list matches))) (match (filter-map cpe-match->cve-configuration matches) (() #f) ((one) one) (lst (cons operator lst)))))) ((assoc-ref node "children") ;typically for 'and' => (lambda (children) (match (filter-map node->configuration (vector->list children)) (() #f) ((one) one) (lst (cons operator lst))))) (else #f)))) (let ((nodes (vector->list (assoc-ref alist "nodes")))) (filter-map node->configuration nodes))) (define (json->cve-items json) "Parse JSON, an input port or a string, and return a list of records." (let* ((alist (json->scm json)) (type (assoc-ref alist "CVE_data_type")) (format (assoc-ref alist "CVE_data_format")) (version (assoc-ref alist "CVE_data_version"))) (unless (equal? type "CVE") (raise (condition (&message (message "invalid CVE feed"))))) (unless (equal? format "MITRE") (raise (formatted-message (G_ "unsupported CVE format: '~a'") format))) (unless (equal? version "4.0") (raise (formatted-message (G_ "unsupported CVE data version: '~a'") version))) (map json->cve-item (vector->list (assoc-ref alist "CVE_Items"))))) (define (version-matches? version sexp) "Return true if VERSION, a string, matches SEXP." (match sexp ('_ #t) ((? string? expected) (version-prefix? expected version)) (('or sexps ...) (any (cut version-matches? version <>) sexps)) (('and sexps ...) (every (cut version-matches? version <>) sexps)) (('< max) (version>? max version)) (('<= max) (version>=? max version)) (('> min) (version>? version min)) (('>= min) (version>=? version min)))) (define (vulnerability-matches? vuln vendor hidden-vendors) "Checks if a VENDOR matches at least one of VULN packages. When VENDOR is #f, ignore packages that have a vendor among HIDDEN-VENDORS." (define hidden-vendor? (if (list? hidden-vendors) (cut member <> hidden-vendors) (const #f))) (match vuln (($ id packages) (any (match-lambda ((? (cut string=? <> vendor)) #t) ((? hidden-vendor?) #f) (otherwise (not vendor))) (map car packages))))) ;candidate vendors ;;; ;;; High-level interface. ;;; (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://nvd.nist.gov/feeds/json/cve/1.1/nvdcve-1.1-" (number->string year) ".json.gz"))) (define %current-year-ttl ;; According to , feeds are ;; updated "approximately every two hours." (* 60 30)) (define %past-year-ttl ;; Update the previous year's database more and more infrequently. (* 3600 24 (date-month %now))) (define-record-type (vulnerability id packages) vulnerability? (id vulnerability-id) ;string (packages vulnerability-packages)) ;((v1 p1 sexp1) (v2 p2 sexp2) ...) (define vulnerability->sexp (match-lambda (($ id packages) `(v ,id ,packages)))) (define sexp->vulnerability (match-lambda (('v id (packages ...)) (vulnerability id packages)))) (define (cve-configuration->package-list config) "Parse CONFIG, a config sexp, and return a list of the form (V P SEXP) where V is a CPE vendor, P is a package name and SEXP expresses constraints on the matching versions." (let loop ((config config) (results '())) (match config (('or configs ...) (fold loop results configs)) (('and config _ ...) ;XXX (loop config results)) (((? string? vendor) (? string? package) sexp) (let ((pruned-results (remove (match-lambda ((vendor package _) #t) (otherwise #f)) results))) (match sexp ('_ ;any version (cons `(,vendor ,package _) pruned-results)) (_ (match (assoc-ref (assoc-ref results vendor) package) ((previous) (cons `(,vendor ,package (or ,sexp ,previous)) pruned-results)) (_ (cons `(,vendor ,package ,sexp) results)))))))))) (define (merge-package-lists lst) "Merge the list in LST, each of which has the form (V P SEXP), where V is a CPE vendor, P is the name of a package and SEXP is an sexp that constrains matching versions." (fold (lambda (plist result) ;XXX: quadratic (fold (match-lambda* (((vendor package version) result) (match (assoc-ref result vendor) (((? (cut string=? package <>)) previous) (cons `(,vendor ,package (or ,version ,previous)) (remove (match-lambda ((vendor package _) #t) (otherwise #f)) result))) (_ (cons `(,vendor ,package ,version) result))))) result plist)) '() lst)) (define (cve-item->vulnerability item) "Return a corresponding to ITEM, a record; return #f if ITEM does not list any configuration or if it does not list any \"a\" (application) configuration." (let ((id (cve-id (cve-item-cve item)))) (match (cve-item-configurations item) (() ;no configurations #f) ((configs ...) (vulnerability id (merge-package-lists (map cve-configuration->package-list configs))))))) (define (json->vulnerabilities json) "Parse JSON, an input port or a string, and return the list of vulnerabilities found therein." (filter-map cve-item->vulnerability (json->cve-items json))) (define (write-cache input cache) "Read vulnerabilities as gzipped JSON from INPUT, and write it as a compact sexp to CACHE." (call-with-decompressed-port 'gzip input (lambda (input) (define vulns (json->vulnerabilities input)) (write `(vulnerabilities 2 ;format version ,(map vulnerability->sexp vulns)) cache)))) (define* (fetch-vulnerabilities year ttl #:key (timeout 10)) "Return the list of for YEAR, assuming the on-disk cache has the given TTL (fetch from the NIST web site when TTL has expired)." (define (cache-miss uri) (format (current-error-port) "fetching CVE database for ~a...~%" year)) (define (read* port) ;; Disable read options to avoid populating the source property weak ;; table, which speeds things up, saves memory, and works around ;; . (let ((options (read-options))) (dynamic-wind (lambda () (read-disable 'positions)) (lambda () (read port)) (lambda () (read-options options))))) ;; Note: We used to keep the original JSON files in cache but parsing it ;; would take typically ~15s for a year of data. Thus, we instead store a ;; summarized version thereof as an sexp, which can be parsed in 1s or so. (let* ((port (http-fetch/cached (yearly-feed-uri year) #:ttl ttl #:write-cache write-cache #:cache-miss cache-miss #:timeout timeout)) (sexp (read* port))) (close-port port) (match sexp (('vulnerabilities 1 vulns) (map sexp->vulnerability vulns))))) (define* (current-vulnerabilities #:key (timeout 10)) "Return the current list of Common Vulnerabilities and Exposures (CVE) as published by the US NIST. TIMEOUT specifies the timeout in seconds for connection establishment." (let ((past-years (unfold (cut > <> 3) (lambda (n) (- %current-year n)) 1+ 1)) (past-ttls (unfold (cut > <> 3) (lambda (n) (* n %past-year-ttl)) 1+ 1))) (append-map (cut fetch-vulnerabilities <> <> #:timeout timeout) (cons %current-year past-years) (cons %current-year-ttl past-ttls)))) (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 vulnerabilities; otherwise, it returns a list of vulnerabilities affecting the given package version." (define table ;; Map package names to lists of version/vulnerability pairs. (fold (lambda (vuln table) (match vuln (($ id packages) (fold (lambda (package table) (match package ((vendor name versions) (vhash-cons name (cons vuln `(,versions)) table)))) table packages)))) vlist-null vulnerabilities)) (lambda* (package #:optional version #:key (vendor #f) (hidden-vendors '())) (vhash-fold* (lambda (pair result) (match pair ((vuln sexp) (if (and (or (and (not vendor) (null? hidden-vendors)) (vulnerability-matches? vuln vendor hidden-vendors)) (or (not version) (version-matches? version sexp))) (cons vuln result) result)))) '() package table))) ;;; cve.scm ends here