From 9bee0dffaebbc53b9762df7a6d84a553969e7b00 Mon Sep 17 00:00:00 2001

From: rpm-build <rpm-build>

Date: Fri, 3 Feb 2017 09:36:26 +0100

Subject: [PATCH 3/8] Drop root priviledges before opening first savefile if

 running with -Z root

---

 tcpdump.1.in |  7 ++++++-

 tcpdump.c    | 30 ++++++++++++++++++++++++++++++

 2 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/tcpdump.1.in b/tcpdump.1.in

index f04a579..ca5cff2 100644

--- a/tcpdump.1.in

+++ b/tcpdump.1.in

@@ -249,6 +249,9 @@ have the name specified with the

 flag, with a number after it, starting at 1 and continuing upward.

 The units of \fIfile_size\fP are millions of bytes (1,000,000 bytes,

 not 1,048,576 bytes).

+

+Note that when used with \fB\-Z\fR option (enabled by default), privileges

+are dropped before opening the first savefile.

 .TP

 .B \-d

 Dump the compiled packet-matching code in a human readable form to

@@ -860,7 +863,9 @@ but before opening any savefiles for output, change the user ID to

 and the group ID to the primary group of

 .IR user .

 .IP

-This behavior can also be enabled by default at compile time.

+This behavior is enabled by default (\fB\-Z tcpdump\fR), and can

+be disabled by \fB\-Z root\fR.

+

 .IP "\fI expression\fP"

 .RS

 selects which packets will be dumped.

@@ -366,6 +366,10 @@ If no time format is specified, each new file will overwrite the previous.

 If used in conjunction with the

 .B \-C

 option, filenames will take the form of `\fIfile\fP<count>'.

+.IP

+Note that when used with 

+.B \-Z 

+option (enabled by default), privileges are dropped before opening the first savefile.

 .TP

 .B \-h

 .PD 0

diff --git a/tcpdump.c b/tcpdump.c

index 73bf138..29f7f87 100644

--- a/tcpdump.c

+++ b/tcpdump.c

@@ -1133,6 +1133,7 @@ main(int argc, char **argv)

 	cap_rights_t rights;

 	int cansandbox;

 #endif	/* HAVE_CAPSICUM */

+	int chown_flag = 0;

 	int Oflag = 1;			/* run filter code optimizer */

 	int yflag_dlt = -1;

 	const char *yflag_dlt_name = NULL;

@@ -1843,6 +1844,19 @@ main(int argc, char **argv)

 		}

 		capng_apply(CAPNG_SELECT_BOTH);

 #endif /* HAVE_LIBCAP_NG */

+	/* If user is running tcpdump as root and wants to write to the savefile,

+	 * we will check if -C is set and if it is, we will drop root

+	 * privileges right away and consequent call to>pcap_dump_open()

+	 * will most likely fail for the first file. If -C flag is not set we

+	 * will create file as root then change ownership of file to proper

+	 * user(default tcpdump) and drop root privileges.

+	 */

+	if (WFileName)

+		if ((Cflag || Gflag) && (username || chroot_dir))

+			droproot(username, chroot_dir);

+		else

+			chown_flag = 1;

+	else

 		if (username || chroot_dir)

 			droproot(username, chroot_dir);

@@ -1881,6 +1895,22 @@ main(int argc, char **argv)

 		  MakeFilename(dumpinfo.CurrentFileName, WFileName, 0, 0);

 		p = pcap_dump_open(pd, dumpinfo.CurrentFileName);

+

+	/* Change ownership of file and drop root privileges */

+	if (chown_flag) {

+		struct passwd *pwd;

+

+		pwd = getpwnam(username);

+		if (!pwd)

+			error("Couldn't find user '%s'", username);

+

+		if (strcmp(WFileName, "-") && chown(dumpinfo.CurrentFileName, pwd->pw_uid, pwd->pw_gid) < 0)

+			error("Couldn't change ownership of savefile");

+

+		if (username || chroot_dir)

+			droproot(username, chroot_dir);

+    }

+

 #ifdef HAVE_LIBCAP_NG

 		/* Give up CAP_DAC_OVERRIDE capability.

 		 * Only allow it to be restored if the -C or -G flag have been

-- 

2.9.3