sys-devel/bc: add support for --sandbox & USE=forced-sandbox

The dc tool has an ! command which allows for arbitrary system() calls
which is not ideal for processing arbitrary user scripts.  First add
support for a --sandbox flag at runtime (like sed/gawk gnu tools),
then add a USE=forced-sandbox option so people can lock it down.

The patches have been sent to upstream, but considering how slow the
bc project tends to move, and their lack of a project site/git repo,
going to merge this now and just wait for upstream feedback.

3 files changed, 189 insertions, 0 deletions

diff --git a/sys-devel/bc/bc-1.07.1-r2.ebuild b/sys-devel/bc/bc-1.07.1-r2.ebuild
new file mode 100644
index 000000000000..78cc0f0805f4
--- /dev/null
+++ b/sys-devel/bc/bc-1.07.1-r2.ebuild
@@ -0,0 +1,65 @@
+# Copyright 1999-2018 Gentoo Foundation
+# Distributed under the terms of the GNU General Public License v2
+
+EAPI="6"
+
+inherit flag-o-matic toolchain-funcs
+
+DESCRIPTION="Handy console-based calculator utility"
+HOMEPAGE="https://www.gnu.org/software/bc/bc.html"
+SRC_URI="mirror://gnu/bc/${P}.tar.gz"
+
+LICENSE="GPL-2 LGPL-2.1"
+SLOT="0"
+KEYWORDS="~alpha ~amd64 ~arm ~arm64 ~hppa ~ia64 ~m68k ~mips ~ppc ~ppc64 ~s390 ~sh ~sparc ~x86 ~ppc-aix ~x64-cygwin ~amd64-fbsd ~x86-fbsd ~amd64-linux ~x86-linux ~ppc-macos ~x64-macos ~x86-macos ~m68k-mint ~sparc-solaris ~sparc64-solaris ~x64-solaris ~x86-solaris"
+IUSE="forced-sandbox libedit readline static"
+
+RDEPEND="
+	!readline? ( libedit? ( dev-libs/libedit:= ) )
+	readline? (
+		>=sys-libs/readline-4.1:0=
+		>=sys-libs/ncurses-5.2:=
+	)
+"
+DEPEND="
+	${RDEPEND}
+	sys-apps/ed
+	sys-devel/flex
+	virtual/yacc
+"
+
+PATCHES=(
+	"${FILESDIR}/${PN}-1.07.1-sandbox.patch"
+)
+
+src_prepare() {
+	default
+
+	# A patch to make this into a configure option has been sent upstream,
+	# but lets avoid regenerating all the autotools just for this.
+	if use forced-sandbox ; then
+		sed -i '/dc_sandbox_enabled = 0/s:0:1:' dc/dc.c || die
+	fi
+}
+
+src_configure() {
+	local myconf=(
+		$(use_with readline)
+	)
+	if use readline ; then
+		myconf+=( --without-libedit )
+	else
+		myconf+=( $(use_with libedit) )
+	fi
+	use static && append-ldflags -static
+
+	econf "${myconf[@]}"
+
+	# Do not regen docs -- configure produces a small fragment that includes
+	# the version info which causes all pages to regen (newer file). #554774
+	touch -r doc doc/*
+}
+
+src_compile() {
+	emake AR="$(tc-getAR)"
+}
diff --git a/sys-devel/bc/files/bc-1.07.1-sandbox.patch b/sys-devel/bc/files/bc-1.07.1-sandbox.patch
new file mode 100644
index 000000000000..ec5c406645b2
--- /dev/null
+++ b/sys-devel/bc/files/bc-1.07.1-sandbox.patch
@@ -0,0 +1,121 @@
+this has been sent upstream, but they don't have a mailing list or project site
+to link to.  oh well.
+
+From e641584767c3c7cc1ff544805acc2562fc56cda9 Mon Sep 17 00:00:00 2001
+From: Mike Frysinger <vapier@chromium.org>
+Date: Mon, 17 Sep 2018 18:57:57 -0400
+Subject: [PATCH 1/2] dc: add a --sandbox option
+
+Other GNU projects (like sed & gawk) have a --sandbox flag whereby
+access to files and system() are disabled.  This allows people to
+run arbitrary scripts without worrying about them "escaping" and
+executing arbitrary commands on the system.
+---
+ dc/dc.c     | 9 ++++++++-
+ dc/dc.h     | 3 +++
+ dc/misc.c   | 6 ++++++
+ doc/dc.1    | 5 +++++
+ doc/dc.texi | 4 ++++
+ 5 files changed, 26 insertions(+), 1 deletion(-)
+
+diff --git a/dc/dc.c b/dc/dc.c
+index 6a2bb2639235..592a76be71da 100644
+--- a/dc/dc.c
++++ b/dc/dc.c
+@@ -54,6 +54,7 @@
+ #endif
+ 
+ const char *progname;	/* basename of program invocation */
++int dc_sandbox_enabled;	/* whether sandbox mode is enabled */
+ 
+ static void
+ bug_report_info DC_DECLVOID()
+@@ -80,6 +81,7 @@ usage DC_DECLARG((f))
+ Usage: %s [OPTION] [file ...]\n\
+   -e, --expression=EXPR    evaluate expression\n\
+   -f, --file=FILE          evaluate contents of file\n\
++  -S, --sandbox            disable the ! (system) command\n\
+   -h, --help               display this help and exit\n\
+   -V, --version            output version information and exit\n\
+ \n\
+@@ -252,6 +254,7 @@ main DC_DECLARG((argc, argv))
+ 	static struct option const long_opts[] = {
+ 		{"expression", required_argument, NULL, 'e'},
+ 		{"file", required_argument, NULL, 'f'},
++		{"sandbox", no_argument, NULL, 'S'},
+ 		{"help", no_argument, NULL, 'h'},
+ 		{"version", no_argument, NULL, 'V'},
+ 		{NULL, 0, NULL, 0}
+@@ -260,12 +263,13 @@ main DC_DECLARG((argc, argv))
+ 	int c;
+ 
+ 	progname = r1bindex(*argv, '/');
++	dc_sandbox_enabled = 0;
+ 	dc_math_init();
+ 	dc_string_init();
+ 	dc_register_init();
+ 	dc_array_init();
+ 
+-	while ((c = getopt_long(argc, argv, "hVe:f:", long_opts, (int *)0)) != EOF) {
++	while ((c = getopt_long(argc, argv, "hVe:f:S", long_opts, (int *)0)) != EOF) {
+ 		switch (c) {
+ 		case 'e':
+ 			{	dc_data string = dc_makestring(optarg, strlen(optarg));
+@@ -279,6 +283,9 @@ main DC_DECLARG((argc, argv))
+ 			try_file(optarg);
+ 			did_eval = 1;
+ 			break;
++		case 'S':
++			dc_sandbox_enabled = 1;
++			break;
+ 		case 'h':
+ 			usage(stdout);
+ 			return flush_okay();
+diff --git a/dc/dc.h b/dc/dc.h
+index 6a871ad612a5..a148df467a92 100644
+--- a/dc/dc.h
++++ b/dc/dc.h
+@@ -76,4 +76,7 @@ typedef struct {
+ /* This is dc's only global variable: */
+ extern const char *progname;	/* basename of program invocation */
+ 
++/* Whether to run in sandbox mode. */
++extern int dc_sandbox_enabled;
++
+ #endif /* not DC_DEFS_H */
+diff --git a/dc/misc.c b/dc/misc.c
+index cd23602fce32..115be90b03bf 100644
+--- a/dc/misc.c
++++ b/dc/misc.c
+@@ -131,6 +131,12 @@ dc_system DC_DECLARG((s))
+ 	char *tmpstr;
+ 	size_t len;
+ 
++	if (dc_sandbox_enabled) {
++		fprintf(stderr, "%s: ! command disabled in sandbox mode\n",
++				progname);
++		exit(EXIT_FAILURE);
++	}
++
+ 	p = strchr(s, '\n');
+ 	if (p != NULL) {
+ 		len = (size_t) (p - s);
+diff --git a/doc/dc.1 b/doc/dc.1
+index 1c666493e00a..7c4b6fffd616 100644
+--- a/doc/dc.1
++++ b/doc/dc.1
+@@ -84,6 +84,11 @@ to the set of commands to be run while processing the input.
+ Add the commands contained in the file
+ .I script-file
+ to the set of commands to be run while processing the input.
++.TP
++.B -S
++.TP
++.B --sandbox
++Run in sandbox mode where access to \fB!\fR for the system function.
+ .PP
+ If any command-line parameters remain after processing the above,
+ these parameters are interpreted as the names of input files to
+-- 
+2.17.1
+
diff --git a/sys-devel/bc/metadata.xml b/sys-devel/bc/metadata.xml
index 56c124413057..5bdfef6846f9 100644
--- a/sys-devel/bc/metadata.xml
+++ b/sys-devel/bc/metadata.xml
@@ -5,4 +5,7 @@
 	<email>base-system@gentoo.org</email>
 	<name>Gentoo Base System</name>
 </maintainer>
+<use>
+	<flag name="forced-sandbox">Always enable --sandbox mode for simpler/secure runtime (disables the ! command in dc)</flag>
+</use>
 </pkgmetadata>