EECS 598-2 / Winter 2000
Homework Assignment #4

SSH/Smartcard Integration
2/20/2000, Naomaru Itoi (itoi@eecs.umich.edu)
Revised 3/9/2000
Deadline: 3/14/2000

Problem Description
The following steps do not have to be carried out in this order.

1. Install SSH
   Copy /afs/engin.umich.edu/class/w00/eecs598/002/software/src/src/ssh-1.2.27.tar.gz to your directory, configure, compile and install on your operating system (Solaris 2.6, RedHat 6.1, or OpenBSD 2.6).
2. Generate a public / private key pair, place the public key on your home directory in iceaxe.
3. Use sample binary /afs/engin.umich.edu/class/w00/eecs598/002/software/bin/(OS name)/ssh to print out your private key with -K option (e.g., ssh -K login.umich.edu).

   Caution
   

   Make sure to copy your public key (.ssh/identity.pub) into .ssh/authorized_keys in the host you want to log in.

   For example, I generated a key pair on prom.engin, therefore prom has my private key (identity) and my public key (identity.pub) in ~/.ssh. I copied the public key to soso.eecs:~/.ssh/authorized_keys.

   prom% ./ssh -K soso.eecs.umich.edu
   setting printKey flag...
   
   ------------printing key
   p:
   ...
   q:
   ...
   1/p mod q:
   ...
   dp:
   ...
   dq:
   ...
   n:
   ...
   
   ----------------------printing key done
   

4. Card initialization
   Write your private key to the card with jR command in pay.
   Caution
   

   Note that jR command writes the private key to a key number 0x10. When you load this key in your applet by setKeyInstance(), you have to specify this number.

   Write your n of the public key to the file 3f.00/73.68 (sh) on card by sending create APDU and write binary APDU from pay. It should look like this:

   % pay> jR (private key (p, q, 1/p mod q, dp, dq) from ssh -K)
   % pay> f 3f.00
   /* create file "sh" */
   % pay> ic f0 E0 00 00 10
   01 00 73 68 02 01 00 00 FF 00 00 00 00 00 00 00
   /* select */
   % pay> f 73.68
   /* write to "sh" */
   % pay> ic f0 d6 00 00 80
   (public key (n) from ssh -K)
   

5. ssh modification
   
   • Add -s option to enable smartcard authentication.
   • Identify RSA decryption operation in ssh. Replace it with a call to smartcard. Implement the equivalent functionality on the card.
   • Identify the part reading n from a private key file. Replace it with a call to smartcard. Implement the equivalent functionality on the card.
   Now your ssh client (with -s option) should let you log on to iceaxe (or whatever) without typing the password.

   Caution
   

   • Large integers are represented by a data structure called MP_INT on SSH, and its byte order is different from one on Cyberflex Access. Use functions in /afs/engin.umich.edu/u/i/t/itoi/eecs598/software/ssh_sc.c to convert MP_INT on SSH to/from buffer on Cyberflex.

Submission
Please place the binary of the modified SSH client (ssh) and the applet (Ssh.bin) in your class directory (/afs/engin.umich.edu/class/w00/eecs598/002/uniqname), and send me e-mail with where your files are, and a couple of paragraphs that explain what your program does.
Your programs must be called "ssh", "Ssh.java", and "Ssh.bin".
I welcome Solaris, Linux, and OpenBSD binaries. If it is absolutely necessary, I will accept others, e.g., Windows binary.

Reference

• Schluberger Cyberflex Access Programming Guide
• /afs/engin.umich.edu/class/w00/eecs598/002/software/src/example/Wallet.java
  You may reuse it.
• Textbook
• ISO 7816-4 spec
• sc7816 library API (/afs/engin.umich.edu/class/w00/eecs598/002/software/src/sc7816/README)
• source files in /afs/engin.umich.edu/class/w00/eecs598/002/software/src/sc7816.
  You may reuse them.

Congratulation, homework #4 is done. As always, send questions to smartcards@umich.edu (I really like receiving questions at smartcards@umich than itoi@eecs because other students can share the information), or talk to us at IRC #smartcards. Obviously, doing more development on ssh/smartcard is more than welcome. For example, ssh with the smartcard on a remote host is an interesting project. If you are interested in doing more, talk to us about potential course projects. Good luck. :)