## PuTTYcard

The idea behind PuTTYcard was to extend the capabilities of PuTTY without adding dependencies to PuTTY. Therefore all smart card routines were realized within a seperate DLL (namely PuTTYcard.dll). Pageant.exe would try to open this DLL. If it could not find it, it would behave like a "normal" Pageant.

This only needed about 20 lines of codes within the source of pageant.exe and I was hoping that the PuTTY team would include this into future PuTTY-packages. They did not :-(

Therefore I merged the source code of PuTTYcard.dll with the source code of pageant.exe and released a smart card enabled version of pageant.exe. If you are interested you may download it at http://smartcard-auth.de/ssh-en.html.

You must register your public key if you want to use some features (for example secure PIN entry). If you used PuTTYcard in the past or are willing to test my smart card enabled version of pageant.exe with a new card or a new card reader I will send you a free licence. Just let me know at pk@….

## PuTTYcard

PuTTYcard is an extension to PuTTY, the free SSH-client from Simon Tatham. With this extension PuTTY can use RSA-keys from external devices, ie. smart cards, usb-tokens.

If pageant is called with one argument, it will interpret this argument as the name of a key-file. Pageant will then load this ppk-file into its keylist, or if another instance of Pageant is already running into the keylist of that instance.

The pageant-version from PuTTYcard-0.58-V1.2.zip (can be downloaded from OpenSCs contrib area) will do exactly the same thing with one exception. If the first line of the ppk-file has the form:

    PuTTYcard,<path to DLL>,<arguments for the DLL>

then Pageant will NOT read the key from the ppk-file. Instead it loads the DLL and calls a function from that DLL passing the arguments from the ppk-file to this function.

The function may then fetch a public RSA key from any source. Possbile choices are: files, smart cards, PKCS11 libraries, Cryptographic Service Providers, etc.

PuTTYcard-0.58-V1.2.zip contains PuTTYiso7816.dll. This DLL will load an RSA key from any ISO-7816-8 compatible smart card. PuTTYiso7816 need additional information from the ppk-file, namely the location of the RSA key on your specific smartcard.

This information is given as 4 hexadecimal numbers, i.e. your ppk-file should look like

    PuTTYcard,PuTTYiso7816.dll,<path>,AA,BB,CCCC

<path> is the DF on your smart card that contains the RSA-key. This must be specified as a 4,8,12 or 16digit hexadecimal number. Do NOT prefix the path with 3F00. AA is the key-reference of the private key, BB is the pin-reference of the pin that protects your private key. CCCC is the ID of a file on your card that contains your public key. This file must either contain the public key as two ASN1-encoded records or it must be a certificate file from which the pulic key will be extracted.

### How do I find the above mentiones numbers?

One of the first actions of PuTTYcard is to change its working DF to the DF given by the <path>-argument. The remaining information (private and public key, PIN and maybe a certificate) will then be read from that DF. Try pkcs15-tool -k to list all of your keys and that should give you the information you need.

Here's the output for my Netkey E4 card:

    $ pkcs15-tool -k
    Private RSA Key [Signatur-Schlüssel]
            Com. Flags  : 1
            Usage       : [0x204], sign, nonRepudiation
            Access Flags: [0x1D], sensitive, alwaysSensitive, neverExtract, local
            ModLength   : 1024
            Key ref     : 128
            Native      : yes
            Path        : DF015331
            Auth ID     : 04
            ID          : 01

    Private RSA Key [Authentifizierungs-Schlüssel]
            Com. Flags  : 1
            Usage       : [0x207], encrypt, decrypt, sign, nonRepudiation
            Access Flags: [0x1D], sensitive, alwaysSensitive, neverExtract, local
            ModLength   : 1024
            Key ref     : 130
            Native      : yes
            Path        : DF015371
            Auth ID     : 04
            ID          : 02

    Private RSA Key [Verschlüsselungs-Schlüssel]
            Com. Flags  : 1
            Usage       : [0x207], encrypt, decrypt, sign, nonRepudiation
            Access Flags: [0x1D], sensitive, alwaysSensitive, neverExtract, local
            ModLength   : 1024
            Key ref     : 129
            Native      : yes
            Path        : DF0153B1
            Auth ID     : 03
            ID          : 03

This card has three keys all of which are stored in DF DF01. This is your <path>-value. Do not include the last component of the path from the pkcs15-tool-output as this is the ID of the private key itself.

The next information you need is the key reference. This value is included as a decimal number in the above output (ie. 128, 130 and 129). This value must be converted to a 2-digit hexadcimal number. Let's use the second key, so your AA-value is 82.

Your private key is protected by a PIN and the pkcs15-tool -k-output contains the Auth-ID of this PIN. Here it is 04. This is not your PIN-reference. Use pkcs15-tool --list-pins to list all your PINs and use the PIN-reference of the PIN that has the same Id as the Auth-Id of your key.

    $ pkcs15-tool --list-pins
    PIN [globale PIN]
            Com. Flags: 0x3
            ID        : 01
            Flags     : [0x51], case-sensitive, initialized, unblockingPin
            Length    : min_len:6, max_len:16, stored_len:16
            Pad char  : 0x00
            Reference : 0
            Type      : ascii-numeric
            Path      : 5000
            Tries left: 3

    PIN [globale PUK]
            Com. Flags: 0x3
            ID        : 02
            Flags     : [0xD1], case-sensitive, initialized, unblockingPin, soPin
            Length    : min_len:8, max_len:16, stored_len:16
            Pad char  : 0x00
            Reference : 1
            Type      : ascii-numeric
            Path      : 5001
            Tries left: 3

    PIN [lokale PIN0]
            Com. Flags: 0x3
            ID        : 03
            Flags     : [0x13], case-sensitive, local, initialized
            Length    : min_len:6, max_len:16, stored_len:16
            Pad char  : 0x00
            Reference : 128
            Type      : ascii-numeric
            Path      : DF015080
            Tries left: 3

    PIN [lokale PIN1]
            Com. Flags: 0x3
            ID        : 04
            Flags     : [0xD3], case-sensitive, local, initialized, unblockingPin, soPin
            Length    : min_len:6, max_len:16, stored_len:16
            Pad char  : 0x00
            Reference : 129
            Type      : ascii-numeric
            Path      : DF015081
            Tries left: 3

Again the PIN-reference is given in decimal (here it is 129) and must be converted to a 2-digit hexdecimal number, namely 81. This is your BB-value.

Finally you need the file-ID of the public key or a certificate file from which he public key could be extracted.

So either use pkcs15-tool --list-public-keys or pkcs15-tool -c. With my Netkey card pkcs15-tool --list-public-keys does not show any keys. This is because my Netkey card contains the public key, but it cannot be used for cryptographic operations. From other sources (ie. card doku) I know that the public key is stored in file DF01:4571, so one possible CCCC-value is 4571.

If I list all my certificates I get:

    $ pkcs15-tool -c
    X.509 Certificate [Telesec Signatur Zertifikat]
            Flags    : 0
            Authority: no
            Path     : DF01C000
            ID       : 01

    X.509 Certificate [User Signatur Zertifikat 1]
            Flags    : 2
            Authority: no
            Path     : DF014331
            ID       : 01

    X.509 Certificate [User Signatur Zertifikat 2]
            Flags    : 2
            Authority: no
            Path     : DF014332
            ID       : 01

    X.509 Certificate [Telesec Authentifizierungs Zertifikat]
            Flags    : 0
            Authority: no
            Path     : DF01C100
            ID       : 02

    X.509 Certificate [User Authentifizierungs Zertifikat 1]
            Flags    : 2
            Authority: no
            Path     : DF014371
            ID       : 02

    X.509 Certificate [Telesec Verschlüsselungs Zertifikat]
            Flags    : 0
            Authority: no
            Path     : DF01C200
            ID       : 03

    X.509 Certificate [User Verschlüsselungs Zertifikat 1]
            Flags    : 2
            Authority: no
            Path     : DF0143B1
            ID       : 03

A certificate contains the right public key, if it has the same ID as the private key (here 02). My card has two such certificates namely DF01:C100 and DF01:4371 so two other possible CCCC-values are C100 and 4371

On a Netkey card a private key may be protected by more than one PIN. So instead of PIN-reference 81 (which references local PIN1) I may alternatively use PIN-reference 00 (which references global PIN0)

So all of the following six lines will work:

    PuTTYcard,PuTTYiso7816.dll,DF01,82,81,4571
    PuTTYcard,PuTTYiso7816.dll,DF01,82,81,C100
    PuTTYcard,PuTTYiso7816.dll,DF01,82,81,4371
    PuTTYcard,PuTTYiso7816.dll,DF01,82,00,4571
    PuTTYcard,PuTTYiso7816.dll,DF01,82,00,C100
    PuTTYcard,PuTTYiso7816.dll,DF01,82,00,4371