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 Using the SSL Debugging Tool

Using the SSL Debugging Tool

Newsgroup: netscape.public.mozilla.crypto
Writer: Sean Cotter
Yell at the manager: Bob Lord

The SSL Debugging Tool is an SSL-aware command-line proxy. It watches TCP connections and displays the data going by. If a connection is SSL, the data display includes interpreted SSL records and handshaking.

Availability

This tool is known to build on Solaris 2.5.1 (SunOS 5.5.1) and Windows NT 4.0.

Description

The ssltap command opens a socket on a rendezvous port and waits for an incoming connection from the client side. Once this connection arrives, the tool makes another connection to the specified host name and port on the server side. It passes any data sent by the client to the server and vice versa. The tool also displays the data to the shell window from which it was called. It can do this for plain HTTP connections or any TCP protocol, as well as for SSL streams, as described here.

The tool cannot and does not decrypt any encrypted message data. You use the tool to look at the plain text and binary data that are part of the handshake procedure, before the secure connection is established.

Syntax

To run the SSL Debugging Tool, type this command in a command shell:

ssltap [-vhfsxl] [-p port] hostname:port

Options

The command does not require any options other than hostname:port, but you normally use them to control the connection interception and output. The options for the command are the following:

-v

Print a version string for the tool.

-h

Turn on hex/ASCII printing. Instead of outputting raw data, the command interprets each record as a numbered line of hex values, followed by the same data as ASCII characters. The two parts are separated by a vertical bar. Nonprinting characters are replaced by dots.

-f

Turn on fancy printing. Output is printed in colored HTML. Data sent from the client to the server is in blue; the server's reply is in red. When used with looping mode, the different connections are separated with horizontal lines. You can use this option to upload the output into a browser.

-s

Turn on SSL parsing and decoding. The tool does not automatically detect SSL sessions. If you are intercepting an SSL connection, use this option so that the tool can detect and decode SSL structures.

If the tool detects a certificate chain, it saves the DER-encoded certificates into files in the current directory. The files are named cert.0x, where x is the sequence number of the certificate.

If the -s option is used with -h, two separate parts are printed for each record: the plain hex/ASCII output, and the parsed SSL output.

-x

Turn on hex/ASCII printing of undecoded data inside parsed SSL records. Used only with the -s option. This option uses the same output format as the -h option.

-l

Turn on looping; that is, continue to accept connections rather than stopping after the first connection is complete.

-p port

Change the default rendezvous port (1924) to another port. The following are well-known port numbers:

HTTP   80

HTTPS   443

SMTP   25

FTP   21

IMAP   143

IMAPS   993 (IMAP over SSL)

NNTP   119

NNTPS   563 (NNTP over SSL)

Examples

You can use the SSL Debugging Tool to intercept any connection information. Although you can run the tool at its most basic by issuing the ssltap command with no options other than hostname:port, the information you get in this way is not very useful.

For example, assume your development machine is called intercept. The simplest way to use the debugging tool is to execute the following command from a command shell:

ssltap www.netscape.com:80
The program waits for an incoming connection on the default port 1924. In your browser window, enter the URL http://intercept:1924. The browser retrieves the requested page from the server at www.netscape.com, but the page is intercepted and passed on to the browser by the debugging tool on intercept.

On its way to the browser, the data is printed to the command shell from which you issued the command. Data sent from the client to the server is surrounded by the following symbols:

--> [ data ]

Data sent from the server to the client is surrounded by the following symbols:

<-- [ data ]

The raw data stream is sent to standard output and is not interpreted in any way. This can result in peculiar effects, such as sounds, flashes, and even crashes of the command shell window. To output a basic, printable interpretation of the data, use the -h option, or, if you are looking at an SSL connection, the -s option.

You will notice that the page you retrieved looks incomplete in the browser. This is because, by default, the tool closes down after the first connection is complete, so the browser is not able to load images. To make the tool continue to accept connections, switch on looping mode with the -l option.

The following examples show the output from commonly used combinations of options.

Example 1

The s and x options in this example turn on SSL parsing and show undecoded values in hex/ASCII format. The output is routed to a text file.

Command 
ssltap.exe -sx -p 444 interzone.mcom.com:443 > sx.txt
Output 
Connected to interzone.mcom.com:443
--> [
alloclen = 66 bytes
   [ssl2]  ClientHelloV2 {
            version = {0x03, 0x00}
            cipher-specs-length = 39 (0x27)
            sid-length = 0 (0x00)
            challenge-length = 16 (0x10)
            cipher-suites = {
                (0x010080) SSL2/RSA/RC4-128/MD5
                  (0x020080) SSL2/RSA/RC4-40/MD5
                  (0x030080) SSL2/RSA/RC2CBC128/MD5
                  (0x040080) SSL2/RSA/RC2CBC40/MD5
                  (0x060040) SSL2/RSA/DES64CBC/MD5
                  (0x0700c0) SSL2/RSA/3DES192EDE-CBC/MD5
                  (0x000004) SSL3/RSA/RC4-128/MD5
                  (0x00ffe0) SSL3/RSA-FIPS/3DES192EDE-CBC/SHA
                  (0x00000a) SSL3/RSA/3DES192EDE-CBC/SHA
                  (0x00ffe1) SSL3/RSA-FIPS/DES64CBC/SHA
                  (0x000009) SSL3/RSA/DES64CBC/SHA
                  (0x000003) SSL3/RSA/RC4-40/MD5
                  (0x000006) SSL3/RSA/RC2CBC40/MD5
                  }
            session-id = { }
            challenge = { 0xec5d 0x8edb 0x37c9 0xb5c9 0x7b70 0x8fe9 0xd1d3
0x2592 }
}
]
<-- [
SSLRecord {
   0: 16 03 00 03  e5                                   |.....
   type    = 22 (handshake)
   version = { 3,0 }
   length  = 997 (0x3e5)
   handshake {
   0: 02 00 00 46                                      |...F
      type = 2 (server_hello)
      length = 70 (0x000046)
            ServerHello {
            server_version = {3, 0}
            random = {...}
   0: 77 8c 6e 26  6c 0c ec c0  d9 58 4f 47  d3 2d 01 45  |
wn&amp;l.ì..XOG.-.E
   10: 5c 17 75 43  a7 4c 88 c7  88 64 3c 50  41 48 4f 7f  |
\.uC§L.Ç.d&lt;PAHO.
                  session ID = {
                  length = 32
                contents = {..}
   0: 14 11 07 a8  2a 31 91 29  11 94 40 37  57 10 a7 32  | ...¨*1.)..@7W.§2
   10: 56 6f 52 62  fe 3d b3 65  b1 e4 13 0f  52 a3 c8 f6  | VoRbþ=³e±...R£È.
         }
               cipher_suite = (0x0003) SSL3/RSA/RC4-40/MD5
         }
   0: 0b 00 02 c5                                      |...Å
      type = 11 (certificate)
      length = 709 (0x0002c5)
            CertificateChain {
            chainlength = 706 (0x02c2)
               Certificate {
            size = 703 (0x02bf)
               data = { saved in file 'cert.001' }
            }
         }
   0: 0c 00 00 ca                                      |....
         type = 12 (server_key_exchange)
         length = 202 (0x0000ca)
   0: 0e 00 00 00                                      |....
         type = 14 (server_hello_done)
         length = 0 (0x000000)
   }
}
]
--> [
SSLRecord {
   0: 16 03 00 00  44                                   |....D
   type    = 22 (handshake)
   version = { 3,0 }
   length  = 68 (0x44)
   handshake {
   0: 10 00 00 40                                      |...@
   type = 16 (client_key_exchange)
   length = 64 (0x000040)
         ClientKeyExchange {
            message = {...}
         }
   }
}
]
--> [
SSLRecord {
   0: 14 03 00 00  01                                   |.....
   type    = 20 (change_cipher_spec)
   version = { 3,0 }
   length  = 1 (0x1)
   0: 01                                               |.
}
SSLRecord {
   0: 16 03 00 00  38                                   |....8
   type    = 22 (handshake)
   version = { 3,0 }
   length  = 56 (0x38)
               < encrypted >
}
]
<-- [
SSLRecord {
   0: 14 03 00 00  01                                   |.....
   type    = 20 (change_cipher_spec)
   version = { 3,0 }
   length  = 1 (0x1)
   0: 01                                               |.
}
]
<-- [
SSLRecord {
   0: 16 03 00 00  38                                   |....8
   type    = 22 (handshake)
   version = { 3,0 }
   length  = 56 (0x38)
                  < encrypted >
}
]
--> [
SSLRecord {
   0: 17 03 00 01  1f                                   |.....
   type    = 23 (application_data)
   version = { 3,0 }
   length  = 287 (0x11f)
               < encrypted >
}
]
<-- [
SSLRecord {
   0: 17 03 00 00  a0                                   |....
   type    = 23 (application_data)
   version = { 3,0 }
   length  = 160 (0xa0)
               < encrypted >
}
]
<-- [
SSLRecord {
0: 17 03 00 00  df                                   |....ß
   type    = 23 (application_data)
   version = { 3,0 }
   length  = 223 (0xdf)
               < encrypted >
}
SSLRecord {
   0: 15 03 00 00  12                                   |.....
   type    = 21 (alert)
   version = { 3,0 }
   length  = 18 (0x12)
               < encrypted >
}
]
Server socket closed.

Example 2

The -s option turns on SSL parsing. Because the -x option is not used in this example, undecoded values are output as raw data. The output is routed to a text file.

Command 
ssltap.exe -s  -p 444 interzone.mcom.com:443 > s.txt

Output 

Connected to interzone.mcom.com:443
--> [
alloclen = 63 bytes
   [ssl2]  ClientHelloV2 {
            version = {0x03, 0x00}
            cipher-specs-length = 36 (0x24)
            sid-length = 0 (0x00)
            challenge-length = 16 (0x10)
            cipher-suites = {
                  (0x010080) SSL2/RSA/RC4-128/MD5
                  (0x020080) SSL2/RSA/RC4-40/MD5
                  (0x030080) SSL2/RSA/RC2CBC128/MD5
                  (0x060040) SSL2/RSA/DES64CBC/MD5
                  (0x0700c0) SSL2/RSA/3DES192EDE-CBC/MD5
                  (0x000004) SSL3/RSA/RC4-128/MD5
                  (0x00ffe0) SSL3/RSA-FIPS/3DES192EDE-CBC/SHA
                  (0x00000a) SSL3/RSA/3DES192EDE-CBC/SHA
                  (0x00ffe1) SSL3/RSA-FIPS/DES64CBC/SHA
                  (0x000009) SSL3/RSA/DES64CBC/SHA
                  (0x000003) SSL3/RSA/RC4-40/MD5
                  }
               session-id = { }
            challenge = { 0x713c 0x9338 0x30e1 0xf8d6 0xb934 0x7351 0x200c
0x3fd0 }
]
<-- [
SSLRecord {
   type    = 22 (handshake)
   version = { 3,0 }
   length  = 997 (0x3e5)
   handshake {
         type = 2 (server_hello)
         length = 70 (0x000046)
            ServerHello {
            server_version = {3, 0}
            random = {...}
            session ID = {
               length = 32
               contents = {..}
               }
               cipher_suite = (0x0003) SSL3/RSA/RC4-40/MD5
            }
         type = 11 (certificate)
         length = 709 (0x0002c5)
            CertificateChain {
               chainlength = 706 (0x02c2)
               Certificate {
                  size = 703 (0x02bf)
                  data = { saved in file 'cert.001' }
               }
            }
         type = 12 (server_key_exchange)
         length = 202 (0x0000ca)
         type = 14 (server_hello_done)
         length = 0 (0x000000)
   }
}
]
--> [
SSLRecord {
   type    = 22 (handshake)
   version = { 3,0 }
   length  = 68 (0x44)
   handshake {
         type = 16 (client_key_exchange)
         length = 64 (0x000040)
            ClientKeyExchange {
               message = {...}
            }
   }
}
]
--> [
SSLRecord {
   type    = 20 (change_cipher_spec)
   version = { 3,0 }
   length  = 1 (0x1)
}
SSLRecord {
   type    = 22 (handshake)
   version = { 3,0 }
   length  = 56 (0x38)
               < encrypted >
}
]
<-- [
SSLRecord {
   type    = 20 (change_cipher_spec)
   version = { 3,0 }
   length  = 1 (0x1)
}
]
<-- [
SSLRecord {
   type    = 22 (handshake)
   version = { 3,0 }
   length  = 56 (0x38)
               < encrypted >
}
]
--> [
SSLRecord {
   type    = 23 (application_data)
   version = { 3,0 }
   length  = 287 (0x11f)
               < encrypted >
}
]
[
SSLRecord {
   type    = 23 (application_data)
   version = { 3,0 }
   length  = 160 (0xa0)
               < encrypted >
}
]
<-- [
SSLRecord {
   type    = 23 (application_data)
   version = { 3,0 }
   length  = 223 (0xdf)
               < encrypted >
}
SSLRecord {
   type    = 21 (alert)
   version = { 3,0 }
   length  = 18 (0x12)
               < encrypted >
}
]
Server socket closed.

Example 3

In this example, the -h option turns hex/ASCII format. There is no SSL parsing or decoding. The output is routed to a text file.

Command 
ssltap.exe -h  -p 444 interzone.mcom.com:443 > h.txt
Output 
Connected to interzone.mcom.com:443
--> [
   0: 80 40 01 03  00 00 27 00  00 00 10 01  00 80 02 00  | .@....'.........
   10: 80 03 00 80  04 00 80 06  00 40 07 00  c0 00 00 04  | .........@......
   20: 00 ff e0 00  00 0a 00 ff  e1 00 00 09  00 00 03 00  | ........á.......
   30: 00 06 9b fe  5b 56 96 49  1f 9f ca dd  d5 ba b9 52  | ..þ[V.I.\xd9 ...º¹R
   40: 6f 2d                                            |o-
]
<-- [
   0: 16 03 00 03  e5 02 00 00  46 03 00 7f  e5 0d 1b 1d  | ........F.......
   10: 68 7f 3a 79  60 d5 17 3c  1d 9c 96 b3  88 d2 69 3b  | h.:y`..&lt;..³.Òi;
   20: 78 e2 4b 8b  a6 52 12 4b  46 e8 c2 20  14 11 89 05  | x.K.¦R.KFè. ...
   30: 4d 52 91 fd  93 e0 51 48  91 90 08 96  c1 b6 76 77  | MR.ý..QH.....¶vw
   40: 2a f4 00 08  a1 06 61 a2  64 1f 2e 9b  00 03 00 0b  | *ô..¡.a¢d......
   50: 00 02 c5 00  02 c2 00 02  bf 30 82 02  bb 30 82 02  | ..Å......0...0..
   60: 24 a0 03 02  01 02 02 02  01 36 30 0d  06 09 2a 86  | $ .......60...*.
   70: 48 86 f7 0d  01 01 04 05  00 30 77 31  0b 30 09 06  | H.÷......0w1.0..
   80: 03 55 04 06  13 02 55 53  31 2c 30 2a  06 03 55 04  | .U....US1,0*..U.
   90: 0a 13 23 4e  65 74 73 63  61 70 65 20  43 6f 6d 6d  | ..#Netscape Comm
   a0: 75 6e 69 63  61 74 69 6f  6e 73 20 43  6f 72 70 6f  | unications Corpo
   b0: 72 61 74 69  6f 6e 31 11  30 0f 06 03  55 04 0b 13  | ration1.0...U...
   c0: 08 48 61 72  64 63 6f 72  65 31 27 30  25 06 03 55  | .Hardcore1'0%..U
   d0: 04 03 13 1e  48 61 72 64  63 6f 72 65  20 43 65 72  | ....Hardcore Cer
   e0: 74 69 66 69  63 61 74 65  20 53 65 72  76 65 72 20  | tificate Server
   f0: 49 49 30 1e  17 0d 39 38  30 35 31 36  30 31 30 33  | II0...9805160103
<additional data lines>
]
<additional records in same format>
Server socket closed.

Example 4

In this example, the -s option turns on SSL parsing, and the -h options turns on hex/ASCII format. Both formats are shown for each record. The output is routed to a text file.

Command 
ssltap.exe -hs -p 444 interzone.mcom.com:443 > hs.txt
Output 
Connected to interzone.mcom.com:443
--> [
   0: 80 3d 01 03  00 00 24 00  00 00 10 01  00 80 02 00  | .=....$.........
   10: 80 03 00 80  04 00 80 06  00 40 07 00  c0 00 00 04  | .........@......
   20: 00 ff e0 00  00 0a 00 ff  e1 00 00 09  00 00 03 03  | ........á.......
   30: 55 e6 e4 99  79 c7 d7 2c  86 78 96 5d  b5 cf e9     |U..yÇ\xb0 ,.x.]µÏé
alloclen = 63 bytes
   [ssl2]  ClientHelloV2 {
            version = {0x03, 0x00}
            cipher-specs-length = 36 (0x24)
            sid-length = 0 (0x00)
            challenge-length = 16 (0x10)
            cipher-suites = {
                  (0x010080) SSL2/RSA/RC4-128/MD5
                  (0x020080) SSL2/RSA/RC4-40/MD5
                  (0x030080) SSL2/RSA/RC2CBC128/MD5
                  (0x040080) SSL2/RSA/RC2CBC40/MD5
                  (0x060040) SSL2/RSA/DES64CBC/MD5
                  (0x0700c0) SSL2/RSA/3DES192EDE-CBC/MD5
                  (0x000004) SSL3/RSA/RC4-128/MD5
                  (0x00ffe0) SSL3/RSA-FIPS/3DES192EDE-CBC/SHA
                  (0x00000a) SSL3/RSA/3DES192EDE-CBC/SHA
                  (0x00ffe1) SSL3/RSA-FIPS/DES64CBC/SHA
                  (0x000009) SSL3/RSA/DES64CBC/SHA
                  (0x000003) SSL3/RSA/RC4-40/MD5
                  }
            session-id = { }
            challenge = { 0x0355 0xe6e4 0x9979 0xc7d7 0x2c86 0x7896 0x5db

0xcfe9 }
}
]
<additional records in same formats>
Server socket closed.

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Last modified January 18, 2000.