From 26ecdf53960658771c0fc582f72a4025e2887f75 Mon Sep 17 00:00:00 2001
From: Phil Sutter <phil@nwl.cc>
Date: Tue, 18 Jan 2022 22:39:08 +0100
Subject: xshared: Fix response to unprivileged users

Expected behaviour in both variants is:

* Print help without error, append extension help if -m and/or -j
  options are present
* Indicate lack of permissions in an error message for anything else

With iptables-nft, this was broken basically from day 1. Shared use of
do_parse() then somewhat broke legacy: it started complaining about
inability to create a lock file.

Fix this by making iptables-nft assume extension revision 0 is present
if permissions don't allow to verify. This is consistent with legacy.

Second part is to exit directly after printing help - this avoids having
to make the following code "nop-aware" to prevent privileged actions.

Conflict: NA
Reference:
https://git.netfilter.org/iptables/commit/?id=26ecdf53960658771c0fc582f72a4025e2887f75
Signed-off-by: Phil Sutter <phil@nwl.cc>
Reviewed-by: Florian Westphal <fw@strlen.de>
---
 iptables/nft.c                                |  5 ++
 .../testcases/iptables/0008-unprivileged_0    | 59 +++++++++++++++++++
 iptables/xtables.c                            |  2 +-
 3 files changed, 65 insertions(+), 1 deletion(-)
 create mode 100644 iptables/tests/shell/testcases/iptables/0008-unprivileged_0

diff --git a/iptables/nft.c b/iptables/nft.c
index bde4ca7..c9a4940 100644
--- a/iptables/nft.c
+++ b/iptables/nft.c
@@ -3245,6 +3245,11 @@ int nft_compatible_revision(const char *name, uint8_t rev, int opt)
 err:
 	mnl_socket_close(nl);
 
+    /* pretend revision 0 is valid if not permitted to check -
+    * this is required for printing extension help texts as user */
+    if (ret < 0 && errno == EPERM && rev == 0)
+        return 1;
+
 	return ret < 0 ? 0 : 1;
 }
 
diff --git a/iptables/tests/shell/testcases/iptables/0008-unprivileged_0 b/iptables/tests/shell/testcases/iptables/0008-unprivileged_0
new file mode 100644
index 0000000..0914c88
--- /dev/null
+++ b/iptables/tests/shell/testcases/iptables/0008-unprivileged_0
@@ -0,0 +1,59 @@
+#!/bin/bash
+# iptables may print match/target specific help texts
+# help output should work for unprivileged users
+
+run() {
+   echo "running: $*" >&2
+   runuser -u nobody -- "$@"
+}
+
+grep_or_rc() {
+   declare -g rc
+   grep -q "$*" && return 0
+   echo "missing in output: $*" >&2
+   return 1
+}
+
+out=$(run $XT_MULTI iptables --help)
+let "rc+=$?"
+grep_or_rc "iptables -h (print this help information)" <<< "$out"
+let "rc+=$?"
+
+out=$(run $XT_MULTI iptables -m limit --help)
+let "rc+=$?"
+grep_or_rc "limit match options:" <<< "$out"
+let "rc+=$?"
+
+out=$(run $XT_MULTI iptables -p tcp --help)
+let "rc+=$?"
+grep_or_rc "tcp match options:" <<< "$out"
+let "rc+=$?"
+
+out=$(run $XT_MULTI iptables -j DNAT --help)
+let "rc+=$?"
+grep_or_rc "DNAT target options:" <<< "$out"
+let "rc+=$?"
+
+out=$(run $XT_MULTI iptables -p tcp -j DNAT --help)
+let "rc+=$?"
+grep_or_rc "tcp match options:" <<< "$out"
+let "rc+=$?"
+out=$(run $XT_MULTI iptables -p tcp -j DNAT --help)
+let "rc+=$?"
+grep_or_rc "DNAT target options:" <<< "$out"
+let "rc+=$?"
+
+
+run $XT_MULTI iptables -L 2>&1 | \
+       grep_or_rc "Permission denied"
+let "rc+=$?"
+
+run $XT_MULTI iptables -A FORWARD -p tcp --dport 123 2>&1 | \
+       grep_or_rc "Permission denied"
+let "rc+=$?"
+
+run $XT_MULTI iptables -A FORWARD -j DNAT --to-destination 1.2.3.4 2>&1 | \
+       grep_or_rc "Permission denied"
+let "rc+=$?"
+
+exit $rc
diff --git a/iptables/xtables.c b/iptables/xtables.c
index 9779bd8..a16bba7 100644
--- a/iptables/xtables.c
+++ b/iptables/xtables.c
@@ -645,7 +645,7 @@ void do_parse(struct nft_handle *h, int argc, char *argv[],
 
 			printhelp(cs->matches);
 			p->command = CMD_NONE;
-			return;
+			exit(0);
 
 			/*
 			 * Option selection
-- 
2.23.0