gnu: Graphviz: Fix CVE-2020-18032.

* gnu/packages/patches/graphviz-CVE-2020-18032.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.
* gnu/packages/graphviz.scm (graphviz)[replacement]: New field.
(graphviz/fixed): New variable.

gnu/local.mk

@@ -1164,6 +1164,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/gpodder-disable-updater.patch		\
   %D%/packages/patches/gpsbabel-fix-i686-test.patch		\
   %D%/packages/patches/grantlee-merge-theme-dirs.patch		\
+  %D%/packages/patches/graphviz-CVE-2020-18032.patch		\
   %D%/packages/patches/grep-timing-sensitive-test.patch		\
   %D%/packages/patches/grocsvs-dont-use-admiral.patch		\
   %D%/packages/patches/gromacs-tinyxml2.patch			\

gnu/packages/graphviz.scm

@@ -62,6 +62,7 @@ (define-module (gnu packages graphviz)
 (define-public graphviz
   (package
     (name "graphviz")
+    (replacement graphviz/fixed)
     (version "2.42.3")
     (source (origin
               (method url-fetch)
@@ -126,6 +127,15 @@ (define-public graphviz
 interfaces for other technical domains.")
     (license license:epl1.0)))
 
+(define-public graphviz/fixed
+  (hidden-package
+    (package
+      (inherit graphviz)
+      (source (origin
+                (inherit (package-source graphviz))
+                (patches (append (search-patches "graphviz-CVE-2020-18032.patch")
+                                 (origin-patches (package-source graphviz)))))))))
+
 ;; Older Graphviz needed for pygraphviz.  See
 ;; https://github.com/pygraphviz/pygraphviz/issues/175
 (define-public graphviz-2.38

gnu/packages/patches/graphviz-CVE-2020-18032.patch

@@ -0,0 +1,49 @@
+Fix CVE-2020-18032:
+
+https://cve.mitre.org/cgi-bin/cvename.cgi?name=2020-18032
+https://gitlab.com/graphviz/graphviz/-/issues/1700
+
+Patch copied from upstream source repository:
+
+https://gitlab.com/graphviz/graphviz/-/commit/784411ca3655c80da0f6025ab20634b2a6ff696b
+
+From 784411ca3655c80da0f6025ab20634b2a6ff696b Mon Sep 17 00:00:00 2001
+From: Matthew Fernandez <matthew.fernandez@gmail.com>
+Date: Sat, 25 Jul 2020 19:31:01 -0700
+Subject: [PATCH] fix: out-of-bounds write on invalid label
+
+When the label for a node cannot be parsed (due to it being malformed), it falls
+back on the symbol name of the node itself. I.e. the default label the node
+would have had if it had no label attribute at all. However, this is applied by
+dynamically altering the node's label to "\N", a shortcut for the symbol name of
+the node. All of this is fine, however if the hand written label itself is
+shorter than the literal string "\N", not enough memory would have been
+allocated to write "\N" into the label text.
+
+Here we account for the possibility of error during label parsing, and assume
+that the label text may need to be overwritten with "\N" after the fact. Fixes
+issue #1700.
+---
+ lib/common/shapes.c | 5 +++--
+ 1 file changed, 3 insertions(+), 2 deletions(-)
+
+diff --git a/lib/common/shapes.c b/lib/common/shapes.c
+index 0a0635fc3..9dca9ba6e 100644
+--- a/lib/common/shapes.c
++++ b/lib/common/shapes.c
+@@ -3546,9 +3546,10 @@ static void record_init(node_t * n)
+     reclblp = ND_label(n)->text;
+     len = strlen(reclblp);
+     /* For some forgotten reason, an empty label is parsed into a space, so
+-     * we need at least two bytes in textbuf.
++     * we need at least two bytes in textbuf, as well as accounting for the
++     * error path involving "\\N" below.
+      */
+-    len = MAX(len, 1);
++    len = MAX(MAX(len, 1), (int)strlen("\\N"));
+     textbuf = N_NEW(len + 1, char);
+     if (!(info = parse_reclbl(n, flip, TRUE, textbuf))) {
+ 	agerr(AGERR, "bad label format %s\n", ND_label(n)->text);
+-- 
+2.31.1
+