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<PRE>
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ssldump - dump SSL traffic on a network
</PRE>
<H2>SYNOPSIS</H2><PRE>
<B>ssldump</B> [ <B>-vtaTnsAxXhHVNdq</B> ] [ <B>-r</B> <I>dumpfile</I> ] [ <B>-i</B> <I>interface</I> ] [ <B>-k</B> <I>keyfile</I> ] [ <B>-p</B> <I>password</I> ] [ <I>expression</I> ]
</PRE>
<H2>DESCRIPTION</H2><PRE>
<I>ssldump</I> is an SSL/TLS network protocol analyzer. It iden-
tifies TCP connections on the chosen network interface and
attempts to interpret them as SSL/TLS traffic. When it
identifies SSL/TLS traffic, it decodes the records and
displays them in a textual form to stdout. If provided
with the appropriate keying material, it will also decrypt
the connections and display the application data traffic.
ssldump has been tested on FreeBSD, Linux, Solaris, and
HP/UX. Since it's based on PCAP, it should work on most
platforms. However, unlike tcpdump, ssldump needs to be
able to see both sides of the data transmission so you may
have trouble using it with network taps such as SunOS nit
that don't permit you to see transmitted data. <B>Under</B>
<B>SunOS</B> <B>with</B> <B>nit</B> <B>or</B> <B>bpf:</B> To run <I>tcpdump</I> you must have read
access to <I>/dev/nit</I> or <I>/dev/bpf*</I>. <B>Under</B> <B>Solaris</B> <B>with</B> <B>dlpi:</B>
You must have read access to the network pseudo device,
e.g. <I>/dev/le</I>. <B>Under</B> <B>HP-UX</B> <B>with</B> <B>dlpi:</B> You must be root or
it must be installed setuid to root. <B>Under</B> <B>IRIX</B> <B>with</B>
<B>snoop:</B> You must be root or it must be installed setuid to
root. <B>Under</B> <B>Linux:</B> You must be root or it must be
installed setuid to root. <B>Under</B> <B>Ultrix</B> <B>and</B> <B>Digital</B> <B>UNIX:</B>
Once the super-user has enabled promiscuous-mode operation
using <B>pfconfig(8)</B>, any user may run <B>ssldump</B> <B>Under</B> <B>BSD:</B> You
must have read access to <I>/dev/bpf*</I>.
</PRE>
<H2>OPTIONS</H2><PRE>
<B>-a</B> Print bare TCP ACKs (useful for observing Nagle behav-
ior)
<B>-A</B> Print all record fields (by default ssldump chooses
the most interesting fields)
<B>-d</B> Display the application data traffic. This usually
means decrypting it, but when -d is used ssldump
will also decode application data traffic _before_
the SSL session initiates. This allows you to see
HTTPS CONNECT behavior as well as SMTP STARTTLS. As
a side effect, since ssldump can't tell whether
plaintext is traffic before the initiation of an
SSL connection or just a regular TCP connection,
this allows you to use ssldump to sniff any TCP
connection. ssldump will automatically detect
ASCII data and display it directly to the screen.
<B>-e</B> Print absolute timestamps instead of relative
timestamps
<B>-r</B> Read data from <I>file</I> instead of from the network.
The old -f option still works but is deprecated and
will probably be removed with the next version. <B>-H</B>
Print the full SSL packet header.
<B>-k</B> Use <I>keyfile</I> as the location of the SSL keyfile
(OpenSSL format) ssldump automatically looks in
./server.pem.
<B>-n</B> Don't try to resolve host names from IP addresses
<B>-N</B> Attempt to parse ASN.1 when it appears, such as in
certificates and DNs.
<B>-p</B> Use <I>password</I> as the SSL keyfile password default is
"password".
<B>-q</B> Don't decode any record fields beyond a single sum-
mary line. (quiet mode).
<B>-x</B> Print each record in hex, as well as decoding it.
<B>-X</B> When the -d option is used, binary data is automat-
ically printed in two columns with a hex dump on
the left and the printable characters on the right.
-X suppresses the display of the printable charac-
ters, thus making it easier to cut and paste the
hext data into some other program. <B>-y</B> Decorate the
output for processing with troff. Not very useful
for the average user.
<I>expression</I>
Selects what packets ssldump will examine. Techni-
cally speaking, ssldump supports the full expres-
sion syntax from PCAP and tcpdump. In fact, the
description here is cribbed from the tcpdump man
page. However, since ssldump needs to examine full
TCP streams, most of the tcpdump expressions will
select traffic mixes that ssldump will simply
ignore. Only the expressions which don't result in
incomplete TCP streams are listed here.
The <I>expression</I> consists of one or more <I>primitives.</I>
Primitives usually consist of an <I>id</I> (name or num-
ber) preceded by one or more qualifiers. There are
three different kinds of qualifier:
are <B>host</B>, <B>net</B> and <B>port</B>. E.g., `host foo',
`net 128.3', `port 20'. If there is no type
qualifier, <B>host</B> is assumed.
<I>dir</I> qualifiers specify a particular transfer
direction to and/or from <I>id.</I> Possible
directions are <B>src</B>, <B>dst</B>, <B>src</B> <B>or</B> <B>dst</B> and <B>src</B>
<B>and</B> <B>dst</B>. E.g., `src foo', `dst net 128.3',
`src or dst port ftp-data'. If there is no
dir qualifier, <B>src</B> <B>or</B> <B>dst</B> is assumed. For
`null' link layers (i.e. point to point pro-
tocols such as slip) the <B>inbound</B> and <B>out-</B>
<B>bound</B> qualifiers can be used to specify a
desired direction.
More complex filter expressions are built up by
using the words <B>and</B>, <B>or</B> and <B>not</B> to combine primi-
tives. E.g., `host foo and not port ftp and not
port ftp-data'. To save typing, identical quali-
fier lists can be omitted. E.g., `tcp dst port ftp
or ftp-data or domain' is exactly the same as `tcp
dst port ftp or tcp dst port ftp-data or tcp dst
port domain'.
Allowable primitives are:
<B>dst</B> <B>host</B> <I>host</I>
True if the IPv4/v6 destination field of the
packet is <I>host</I>, which may be either an
address or a name.
<B>src</B> <B>host</B> <I>host</I>
True if the IPv4/v6 source field of the
packet is <I>host</I>.
<B>host</B> <I>host</I>
True if either the IPv4/v6 source or desti-
nation of the packet is <I>host</I>. Any of the
above host expressions can be prepended with
the keywords, <B>ip</B>, <B>arp</B>, <B>rarp</B>, or <B>ip6</B> as in:
<B>ip</B> <B>host</B> <I>host</I>
which is equivalent to:
<B>ether</B> <B>proto</B> <I>\ip</I> <B>and</B> <B>host</B> <I>host</I>
If <I>host</I> is a name with multiple IP
addresses, each address will be checked for
a match.
<B>ether</B> <B>dst</B> <I>ehost</I>
True if the ethernet destination address is
<I>ehost</I>. <I>Ehost</I> may be either a name from
/etc/ethers or a number (see <B>ethers(3N)</B> for
numeric format).
True if the ethernet source address is
<I>ehost</I>.
<B>ether</B> <B>host</B> <I>ehost</I>
True if either the ethernet source or desti-
nation address is <I>ehost</I>.
<B>gateway</B> <I>host</I>
True if the packet used <I>host</I> as a gateway.
I.e., the ethernet source or destination
address was <I>host</I> but neither the IP source
nor the IP destination was <I>host</I>. <I>Host</I> must
be a name and must be found in both
/etc/hosts and /etc/ethers. (An equivalent
expression is
<B>ether</B> <B>host</B> <I>ehost</I> <B>and</B> <B>not</B> <B>host</B> <I>host</I>
which can be used with either names or num-
bers for <I>host</I> <I>/</I> <I>ehost</I>.) This syntax does
not work in IPv6-enabled configuration at
this moment.
<B>dst</B> <B>net</B> <I>net</I>
True if the IPv4/v6 destination address of
the packet has a network number of <I>net</I>. <I>Net</I>
may be either a name from /etc/networks or a
network number (see <I>networks(4)</I> for
details).
<B>src</B> <B>net</B> <I>net</I>
True if the IPv4/v6 source address of the
packet has a network number of <I>net</I>.
<B>net</B> <I>net</I>
True if either the IPv4/v6 source or desti-
nation address of the packet has a network
number of <I>net</I>.
<B>net</B> <I>net</I> <B>mask</B> <I>mask</I>
True if the IP address matches <I>net</I> with the
specific netmask. May be qualified with <B>src</B>
or <B>dst</B>. Note that this syntax is not valid
for IPv6 <I>net</I>.
<B>net</B> <I>net</I>/<I>len</I>
True if the IPv4/v6 address matches <I>net</I> a
netmask <I>len</I> bits wide. May be qualified
with <B>src</B> or <B>dst</B>.
<B>dst</B> <B>port</B> <I>port</I>
True if the packet is ip/tcp, ip/udp,
ip6/tcp or ip6/udp and has a destination
port value of <I>port</I>. The <I>port</I> can be a num-
both the port number and protocol are
checked. If a number or ambiguous name is
used, only the port number is checked (e.g.,
<B>dst</B> <B>port</B> <B>513</B> will print both tcp/login traf-
fic and udp/who traffic, and <B>port</B> <B>domain</B>
will print both tcp/domain and udp/domain
traffic).
<B>src</B> <B>port</B> <I>port</I>
True if the packet has a source port value
of <I>port</I>.
<B>port</B> <I>port</I>
True if either the source or destination
port of the packet is <I>port</I>. Any of the
above port expressions can be prepended with
the keywords, <B>tcp</B> or <B>udp</B>, as in:
<B>tcp</B> <B>src</B> <B>port</B> <I>port</I>
which matches only tcp packets whose source
port is <I>port</I>.
Primitives may be combined using:
A parenthesized group of primitives and
operators (parentheses are special to the
Shell and must be escaped).
Negation (`<B>!</B>' or `<B>not</B>').
Concatenation (`<B>&amp;&amp;</B>' or `<B>and</B>').
Alternation (`<B>||</B>' or `<B>or</B>').
Negation has highest precedence. Alternation and
concatenation have equal precedence and associate
left to right. Note that explicit <B>and</B> tokens, not
juxtaposition, are now required for concatenation.
If an identifier is given without a keyword, the
most recent keyword is assumed. For example,
<B>not</B> <B>host</B> <B>vs</B> <B>and</B> <B>ace</B>
is short for
<B>not</B> <B>host</B> <B>vs</B> <B>and</B> <B>host</B> <B>ace</B>
which should not be confused with
<B>not</B> <B>(</B> <B>host</B> <B>vs</B> <B>or</B> <B>ace</B> <B>)</B>
Expression arguments can be passed to ssldump as
either a single argument or as multiple arguments,
whichever is more convenient. Generally, if the
expression contains Shell metacharacters, it is
easier to pass it as a single, quoted argument.
Multiple arguments are concatenated with spaces
To listen to traffic on interface <I>le0</I> port <I>443</I>
<B>ssldump</B> <B>-i</B> <B>le0</B> <B>port</B> <B>443</B>
To listen to traffic to the server <I>romeo</I> on port <I>443</I>.
<B>ssldump</B> <B>-i</B> <B>le0</B> <B>port</B> <B>443</B> <B>and</B> <B>host</B> <B>romeo</B>
To decrypt traffic to to host <I>romeo</I> <I>server.pem</I> and the
password <I>foobar</I>
<B>ssldump</B> <B>-Ad</B> <B>-k</B> <B>~/server.pem</B> <B>-p</B> <B>foobar</B> <B>-i</B> <B>le0</B> <B>host</B> <B>romeo</B>
</PRE>
<H2>OUTPUT FORMAT</H2><PRE>
All output is printed to standard out.
ssldump prints an indication of every new TCP connection
using a line like the following
<B>New</B> <B>TCP</B> <B>connection</B> <B>#2:</B> <B>iromeo.rtfm.com(2302)</B> <B>&lt;-&gt;</B> <B>sr1.rtfm.com(4433)</B>
The host which send the first SYN is printed on the left
and the host which responded is printed on the right.
Ordinarily, this means that the SSL client will be printed
on the left with the SSL server on the right. In this case
we have a connection from <I>iromeo.rtfm.com</I> (port <I>2303</I>) to
<I>sr1.rtfm.com</I> (port <I>4433</I>). To allow the user to disentangle
traffic from different connections, each connection is
numbered. This is connection <I>2</I>.
The printout of each SSL record begins with a record line.
This line contains the connection and record number, a
timestamp, and the record type, as in the following:
<B>2</B> <B>3</B> <B>0.2001</B> <B>(0.0749)</B> <B>S&gt;C</B> <B>Handshake</B> <B>Certificate</B>
This is record <I>3</I> on connection <I>2</I>. The first timestamp is
the time since the beginning of the connection. The second
is the time since the previous record. Both are in sec-
onds.
The next field in the record line is the direction that
the record was going. <I>C&gt;S</I> indicates records transmitted
from client to server and <I>S&gt;C</I> indicates records transmit-
ted from server to client. ssldump assumes that the host
to transmit the first SYN is the SSL client (this is
nearly always correct).
The next field is the record type, one of <I>Handshake</I>,
<I>IAlert</I>, <I>ChangeCipherSpec</I>, or <I>application</I><B>_</B><I>data</I>. Finally,
ssldump may print record-specific data on the rest of the
line. For <I>Handshake</I> records, it prints the handshake mes-
sage. Thus, this record is a <I>Certificate</I> message.
ssldump chooses certain record types for further decoding.
<I>ClientHello</I> - version, offered cipher suites, session id
if provided)
<I>ServerHello</I> - version, session_id, chosen cipher suite,
compression method
<I>Alert</I> - type and level (if obtainable)
Fuller decoding of the various records can be obtained by
using the <B>-A</B> , <B>-d</B> , <B>-k</B> and <B>-p</B> flags.
</PRE>
<H2>DECRYPTION</H2><PRE>
ssldump can decrypt traffic between two hosts if the fol-
lowing two conditions are met:
1. ssldump has the keys.
2. Static RSA was used.
In any other case, once encryption starts, ssldump will
only be able to determine the record type. Consider the
following section of a trace.
<B>1</B> <B>5</B> <B>0.4129</B> <B>(0.1983)</B> <B>C&gt;S</B> <B>Handshake</B> <B>ClientKeyExchange</B>
<B>1</B> <B>6</B> <B>0.4129</B> <B>(0.0000)</B> <B>C&gt;S</B> <B>ChangeCipherSpec</B>
<B>1</B> <B>7</B> <B>0.4129</B> <B>(0.0000)</B> <B>C&gt;S</B> <B>Handshake</B>
<B>1</B> <B>8</B> <B>0.5585</B> <B>(0.1456)</B> <B>S&gt;C</B> <B>ChangeCipherSpec</B>
<B>1</B> <B>9</B> <B>0.6135</B> <B>(0.0550)</B> <B>S&gt;C</B> <B>Handshake</B>
<B>1</B> <B>10</B> <B>2.3121</B> <B>(1.6986)</B> <B>C&gt;S</B> <B>application_data</B>
<B>1</B> <B>11</B> <B>2.5336</B> <B>(0.2214)</B> <B>C&gt;S</B> <B>application_data</B>
<B>1</B> <B>12</B> <B>2.5545</B> <B>(0.0209)</B> <B>S&gt;C</B> <B>application_data</B>
<B>1</B> <B>13</B> <B>2.5592</B> <B>(0.0046)</B> <B>S&gt;C</B> <B>application_data</B>
<B>1</B> <B>14</B> <B>2.5592</B> <B>(0.0000)</B> <B>S&gt;C</B> <B>Alert</B>
Note that the <I>ClientKeyExchange</I> message type is printed
but the rest of the <I>Handshake</I> messages do not have types.
These are the <I>Finished</I> messages, but because they are
encrypted ssldump only knows that they are of type <I>Hand-</I>
<I>shake</I>. Similarly, had the <I>Alert</I> in record 14 happened
during the handshake, it's type and level would have been
printed. However, since it is encrypted we can only tell
that it is an alert.
</PRE>
<H2>BUGS</H2><PRE>
Please send bug reports to ssldump@rtfm.com.
The TCP reassembler is not perfect. No attempt is made to
reassemble IP fragments and the 3-way handshake and close
handshake are imperfectly implemented. In practice, this
turns out not to be much of a problem.
Support is provided for only for Ethernet and loopback
interfaces because that's all that I have. If you have
another kind of network you will need to modify pcap_cb in
base/pcap-snoop.c. If you have direct experience with ssldump
on other networks, please send me patches.
ssldump doesn't implement session caching and therefore
can't decrypt resumed sessions.
</PRE>
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