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https://github.com/ThomasDickey/original-mawk/issues/49
From ae3a324a5af1350aa1a6f648e10b9d6656d9fde4 Mon Sep 17 00:00:00 2001
From: Mike Frysinger <vapier@chromium.org>
Date: Tue, 7 Nov 2017 00:41:36 -0500
Subject: [PATCH 1/2] add a -W sandbox mode
This is like gawk's sandbox mode where arbitrary code execution and
file redirection are locked down. This way awk can be a more secure
input/output mode.
---
bi_funct.c | 3 +++
init.c | 8 ++++++++
man/mawk.1 | 4 ++++
mawk.h | 2 +-
scan.c | 6 ++++++
5 files changed, 22 insertions(+), 1 deletion(-)
diff --git a/bi_funct.c b/bi_funct.c
index 7742308c72a5..b524ac8dac8b 100644
--- a/bi_funct.c
+++ b/bi_funct.c
@@ -908,6 +908,9 @@ bi_system(CELL *sp GCC_UNUSED)
#ifdef HAVE_REAL_PIPES
int ret_val;
+ if (sandbox_flag)
+ rt_error("'system' function not allowed in sandbox mode");
+
TRACE_FUNC("bi_system", sp);
if (sp->type < C_STRING)
diff --git a/init.c b/init.c
index 0ab17b003f20..f7babb337e04 100644
--- a/init.c
+++ b/init.c
@@ -40,6 +40,7 @@ typedef enum {
W_RANDOM,
W_SPRINTF,
W_POSIX_SPACE,
+ W_SANDBOX,
W_USAGE
} W_OPTIONS;
@@ -96,6 +97,7 @@ initialize(int argc, char **argv)
int dump_code_flag; /* if on dump internal code */
short posix_space_flag;
+short sandbox_flag;
#ifdef DEBUG
int dump_RE = 1; /* if on dump compiled REs */
@@ -153,6 +155,7 @@ usage(void)
" -W random=number set initial random seed.",
" -W sprintf=number adjust size of sprintf buffer.",
" -W posix_space do not consider \"\\n\" a space.",
+ " -W sandbox disable system() and I/O redirection.",
" -W usage show this message and exit.",
};
size_t n;
@@ -255,6 +258,7 @@ parse_w_opt(char *source, char **next)
DATA(RANDOM),
DATA(SPRINTF),
DATA(POSIX_SPACE),
+ DATA(SANDBOX),
DATA(USAGE)
};
#undef DATA
@@ -389,6 +393,10 @@ process_cmdline(int argc, char **argv)
posix_space_flag = 1;
break;
+ case W_SANDBOX:
+ sandbox_flag = 1;
+ break;
+
case W_RANDOM:
if (haveValue(optNext)) {
int x = atoi(optNext + 1);
diff --git a/man/mawk.1 b/man/mawk.1
index a3c794167dc9..0915d9d7ed5d 100644
--- a/man/mawk.1
+++ b/man/mawk.1
@@ -150,6 +150,10 @@ forces
\fB\*n\fP
not to consider '\en' to be space.
.TP
+\-\fBW \fRsandbox
+runs in a restricted mode where system(), input redirection (e.g. getline),
+output redirection (e.g. print and printf), and pipelines are disabled.
+.TP
\-\fBW \fRrandom=\fInum\fR
calls \fBsrand\fP with the given parameter
(and overrides the auto-seeding behavior).
diff --git a/mawk.h b/mawk.h
index 2d04be1adb34..a6ccc0071ecc 100644
--- a/mawk.h
+++ b/mawk.h
@@ -63,7 +63,7 @@ extern int dump_RE;
#define USE_BINMODE 0
#endif
-extern short posix_space_flag, interactive_flag;
+extern short posix_space_flag, interactive_flag, sandbox_flag;
/*----------------
* GLOBAL VARIABLES
diff --git a/scan.c b/scan.c
index 3a8fc9181ab8..c1833b8b7315 100644
--- a/scan.c
+++ b/scan.c
@@ -455,6 +455,8 @@ yylex(void)
un_next();
if (getline_flag) {
+ if (sandbox_flag)
+ rt_error("redirection not allowed in sandbox mode");
getline_flag = 0;
ct_ret(IO_IN);
} else
@@ -462,6 +464,8 @@ yylex(void)
case SC_GT: /* '>' */
if (print_flag && paren_cnt == 0) {
+ if (sandbox_flag)
+ rt_error("redirection not allowed in sandbox mode");
print_flag = 0;
/* there are 3 types of IO_OUT
-- build the error string in string_buff */
@@ -488,6 +492,8 @@ yylex(void)
un_next();
if (print_flag && paren_cnt == 0) {
+ if (sandbox_flag)
+ rt_error("pipe execution not allowed in sandbox mode");
print_flag = 0;
yylval.ival = PIPE_OUT;
string_buff[0] = '|';
--
2.13.5
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