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From a2ef8d00c53ec9cbd05c4ae2f09b50761130e7ce Mon Sep 17 00:00:00 2001 |
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From: Mathias Kettner <mk@mathias-kettner.de> |
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Date: Mon, 26 May 2014 10:38:16 +0200 |
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Subject: [PATCH] Fix security issue with mk-job on Linux |
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|
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By use of symlinks or hardlinks normal users could inject files to be read |
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with root permissions. This was due to the fact that <tt>/var/lib/check_mk_agent/job</tt> |
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was installed with the permissions <tt>1777</tt>, just as <tt>/tmp</tt>. That way |
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a normal user could have placed a symlink to a file there that is only readable |
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by <tt>root</tt>. The content of that file would then appear in the agent output. |
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|
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This has been fixed by not longer using <tt>/var/lib/check_mk_agent/job</tt> directly, |
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but by creating a separate subdirectory below that for each user. This is done by |
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a new version of <tt>/usr/bin/mk-job</tt>, so please make sure that if you update |
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the agent that you also update <tt>mk-job</tt>. |
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|
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Also you now have to create job subdirectories for non-<tt>root</tt> jobs manually. |
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If you have a job running as user <tt>foo</tt>, then do: |
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|
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C+: |
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RP:mkdir -p /var/lib/check_mk_agent/job |
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RP:chown foo.foo /var/lib/check_mk_agent/job |
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C-: |
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--- |
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diff --git a/ChangeLog b/ChangeLog |
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index 0c9d45e..6ede67a 100644 |
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--- a/ChangeLog |
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+++ b/ChangeLog |
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@@ -56,6 +56,8 @@ |
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NOTE: Please refer to the migration notes! |
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* 0920 blade_bays: now also detects if blade server is switched off |
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* 0977 check_traceroute: new active check for checking presence and absence of routes... |
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+ * 0978 Fix security issue with mk-job on Linux... |
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+ NOTE: Please refer to the migration notes! |
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* 0777 FIX: special agent emcvnx: did not work with security file authentication... |
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* 0786 FIX: zfsget: fixed compatibility with older Solaris agents... |
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* 0809 FIX: brocade_fcport: Fixed recently introduced problem with port speed detection |
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diff --git a/agents/check_mk_agent.linux b/agents/check_mk_agent.linux |
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index 1c9400a..15e416c 100755 |
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--- a/agents/check_mk_agent.linux |
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+++ b/agents/check_mk_agent.linux |
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@@ -495,10 +495,20 @@ then |
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done |
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fi |
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|
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-# Get statistics about monitored jobs |
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-if cd /var/lib/check_mk_agent/job; then |
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+# Get statistics about monitored jobs. Below the job directory there |
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+# is a sub directory per user that ran a job. That directory must be |
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+# owned by the user so that a symlink or hardlink attack for reading |
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+# arbitrary files can be avoided. |
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+if pushd /var/lib/check_mk_agent/job >/dev/null; then |
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echo '<<<job>>>' |
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- head -n -0 -v * |
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+ for username in * |
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+ do |
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+ if [ -d "$username" ] && cd "$username" ; then |
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+ su "$username" -c "head -n -0 -v *" |
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+ cd .. |
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+ fi |
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+ done |
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+ popd > /dev/null |
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fi |
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|
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# Gather thermal information provided e.g. by acpi |
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diff --git a/agents/mk-job b/agents/mk-job |
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index e1df542..04da0c8 100755 |
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--- a/agents/mk-job |
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+++ b/agents/mk-job |
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@@ -39,12 +39,18 @@ if [ $# -lt 2 ]; then |
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exit 1 |
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fi |
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|
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-OUTPUT_PATH=/var/lib/check_mk_agent/job |
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+MYSELF=$(id -nu) |
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+OUTPUT_PATH=/var/lib/check_mk_agent/job/$MYSELF |
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IDENT=$1 |
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shift |
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|
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if [ ! -d "$OUTPUT_PATH" ]; then |
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- mkdir -p "$OUTPUT_PATH" |
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+ if [ "$MYSELF" = root ] ; then |
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+ mkdir -p "$OUTPUT_PATH" |
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+ else |
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+ echo "ERROR: Missing output directory $OUTPUT_PATH for non-root user '$MYSELF'." >&2 |
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+ exit 1 |
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+ fi |
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fi |
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|
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if ! type $1 >/dev/null 2>&1; then |
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-- |
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1.7.10.4 |
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