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114 lines
4.6 KiB
114 lines
4.6 KiB
11 months ago
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From c971d99ffc43df89ca4e15cd81f9e44f4139ba91 Mon Sep 17 00:00:00 2001
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11 months ago
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From: Lennart Poettering <lennart@poettering.net>
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Date: Mon, 31 Aug 2020 19:37:13 +0200
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Subject: [PATCH] pager: set $LESSSECURE whenver we invoke a pager
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Some extra safety when invoked via "sudo". With this we address a
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genuine design flaw of sudo, and we shouldn't need to deal with this.
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But it's still a good idea to disable this surface given how exotic it
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is.
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Prompted by #5666
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(cherry picked from commit 612ebf6c913dd0e4197c44909cb3157f5c51a2f0)
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11 months ago
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Related: #2175624
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11 months ago
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---
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man/less-variables.xml | 8 ++++++++
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man/systemctl.xml | 1 +
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man/systemd.xml | 2 ++
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src/basic/pager.c | 23 +++++++++++++++++++++--
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4 files changed, 32 insertions(+), 2 deletions(-)
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diff --git a/man/less-variables.xml b/man/less-variables.xml
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index a3faa38997..9dad4247da 100644
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--- a/man/less-variables.xml
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+++ b/man/less-variables.xml
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@@ -36,5 +36,13 @@
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the invoking terminal is determined to be UTF-8 compatible).</para></listitem>
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</varlistentry>
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+ <varlistentry id='lesssecure'>
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+ <term><varname>$SYSTEMD_LESSSECURE</varname></term>
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+
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+ <listitem><para>Takes a boolean argument. Overrides the <varname>$LESSSECURE</varname> environment
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+ variable when invoking the pager, which controls the "secure" mode of less (which disables commands
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+ such as <literal>|</literal> which allow to easily shell out to external command lines). By default
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+ less secure mode is enabled, with this setting it may be disabled.</para></listitem>
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+ </varlistentry>
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</variablelist>
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</refsect1>
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diff --git a/man/systemctl.xml b/man/systemctl.xml
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index a71e6c7c4f..abc386e6fb 100644
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--- a/man/systemctl.xml
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+++ b/man/systemctl.xml
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@@ -2010,6 +2010,7 @@ Jan 12 10:46:45 example.com bluetoothd[8900]: gatt-time-server: Input/output err
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<xi:include href="less-variables.xml" xpointer="pager"/>
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<xi:include href="less-variables.xml" xpointer="less"/>
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<xi:include href="less-variables.xml" xpointer="lesscharset"/>
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+ <xi:include href="less-variables.xml" xpointer="lesssecure"/>
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</refsect1>
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<refsect1>
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diff --git a/man/systemd.xml b/man/systemd.xml
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index 17ab59beb5..66ae4d841d 100644
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--- a/man/systemd.xml
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+++ b/man/systemd.xml
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@@ -862,6 +862,8 @@
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</listitem>
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</varlistentry>
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+ <xi:include href="less-variables.xml" xpointer="lesssecure"/>
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+
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<varlistentry>
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<term><varname>$LISTEN_PID</varname></term>
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<term><varname>$LISTEN_FDS</varname></term>
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diff --git a/src/basic/pager.c b/src/basic/pager.c
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index f241261119..4efb01c483 100644
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--- a/src/basic/pager.c
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+++ b/src/basic/pager.c
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@@ -11,6 +11,7 @@
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#include <unistd.h>
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#include "copy.h"
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+#include "env-util.h"
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#include "fd-util.h"
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#include "locale-util.h"
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#include "log.h"
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@@ -94,8 +95,7 @@ int pager_open(bool no_pager, bool jump_to_end) {
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if (setenv("LESS", less_opts, 1) < 0)
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_exit(EXIT_FAILURE);
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- /* Initialize a good charset for less. This is
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- * particularly important if we output UTF-8
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+ /* Initialize a good charset for less. This is particularly important if we output UTF-8
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* characters. */
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less_charset = getenv("SYSTEMD_LESSCHARSET");
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if (!less_charset && is_locale_utf8())
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@@ -104,6 +104,25 @@ int pager_open(bool no_pager, bool jump_to_end) {
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setenv("LESSCHARSET", less_charset, 1) < 0)
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_exit(EXIT_FAILURE);
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+ /* People might invoke us from sudo, don't needlessly allow less to be a way to shell out
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+ * privileged stuff. */
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+ r = getenv_bool("SYSTEMD_LESSSECURE");
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+ if (r == 0) { /* Remove env var if off */
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+ if (unsetenv("LESSSECURE") < 0) {
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+ log_error_errno(errno, "Failed to uset environment variable LESSSECURE: %m");
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+ _exit(EXIT_FAILURE);
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+ }
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+ } else {
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+ /* Set env var otherwise */
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+ if (r < 0)
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+ log_warning_errno(r, "Unable to parse $SYSTEMD_LESSSECURE, ignoring: %m");
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+
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+ if (setenv("LESSSECURE", "1", 1) < 0) {
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+ log_error_errno(errno, "Failed to set environment variable LESSSECURE: %m");
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+ _exit(EXIT_FAILURE);
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+ }
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+ }
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+
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if (pager) {
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execlp(pager, pager, NULL);
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execl("/bin/sh", "sh", "-c", pager, NULL);
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