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From 9bee0dffaebbc53b9762df7a6d84a553969e7b00 Mon Sep 17 00:00:00 2001
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From: rpm-build <rpm-build>
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Date: Fri, 3 Feb 2017 09:36:26 +0100
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Subject: [PATCH 3/8] Drop root priviledges before opening first savefile if
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running with -Z root
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---
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tcpdump.1.in | 7 ++++++-
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tcpdump.c | 30 ++++++++++++++++++++++++++++++
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2 files changed, 36 insertions(+), 1 deletion(-)
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diff --git a/tcpdump.1.in b/tcpdump.1.in
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index f04a579..ca5cff2 100644
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--- a/tcpdump.1.in
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+++ b/tcpdump.1.in
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@@ -249,6 +249,9 @@ have the name specified with the
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flag, with a number after it, starting at 1 and continuing upward.
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The units of \fIfile_size\fP are millions of bytes (1,000,000 bytes,
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not 1,048,576 bytes).
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+
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+Note that when used with \fB\-Z\fR option (enabled by default), privileges
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+are dropped before opening first savefile.
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.TP
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.B \-d
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Dump the compiled packet-matching code in a human readable form to
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@@ -860,7 +863,9 @@ but before opening any savefiles for output, change the user ID to
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and the group ID to the primary group of
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.IR user .
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.IP
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-This behavior can also be enabled by default at compile time.
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+This behavior is enabled by default (\fB\-Z tcpdump\fR), and can
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+be disabled by \fB\-Z root\fR.
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+
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.IP "\fI expression\fP"
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.RS
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selects which packets will be dumped.
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diff --git a/tcpdump.c b/tcpdump.c
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index 73bf138..29f7f87 100644
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--- a/tcpdump.c
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+++ b/tcpdump.c
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@@ -1133,6 +1133,7 @@ main(int argc, char **argv)
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cap_rights_t rights;
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int cansandbox;
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#endif /* HAVE_CAPSICUM */
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+ int chown_flag = 0;
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int Oflag = 1; /* run filter code optimizer */
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int yflag_dlt = -1;
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const char *yflag_dlt_name = NULL;
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@@ -1843,6 +1844,19 @@ main(int argc, char **argv)
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}
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capng_apply(CAPNG_SELECT_BOTH);
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#endif /* HAVE_LIBCAP_NG */
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+ /* If user is running tcpdump as root and wants to write to the savefile,
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+ * we will check if -C is set and if it is, we will drop root
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+ * privileges right away and consequent call to>pcap_dump_open()
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+ * will most likely fail for the first file. If -C flag is not set we
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+ * will create file as root then change ownership of file to proper
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+ * user(default tcpdump) and drop root privileges.
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+ */
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+ if (WFileName)
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+ if (Cflag && (username || chroot_dir))
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+ droproot(username, chroot_dir);
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+ else
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+ chown_flag = 1;
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+ else
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if (username || chroot_dir)
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droproot(username, chroot_dir);
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@@ -1881,6 +1895,22 @@ main(int argc, char **argv)
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MakeFilename(dumpinfo.CurrentFileName, WFileName, 0, 0);
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p = pcap_dump_open(pd, dumpinfo.CurrentFileName);
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+
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+ /* Change ownership of file and drop root privileges */
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+ if (chown_flag) {
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+ struct passwd *pwd;
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+
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+ pwd = getpwnam(username);
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+ if (!pwd)
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+ error("Couldn't find user '%s'", username);
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+
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+ if (strcmp(WFileName, "-") && chown(dumpinfo.CurrentFileName, pwd->pw_uid, pwd->pw_gid) < 0)
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+ error("Couldn't change ownership of savefile");
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+
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+ if (username || chroot_dir)
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+ droproot(username, chroot_dir);
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+ }
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+
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#ifdef HAVE_LIBCAP_NG
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/* Give up CAP_DAC_OVERRIDE capability.
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* Only allow it to be restored if the -C or -G flag have been
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--
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2.9.3
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