Signed Tcl Scripts [Cisco IOS Software Releases 12.4 T]

Table Of Contents

Signed Tcl Scripts

Contents

Prerequisites for Signed Tcl Scripts

Restrictions for Signed Tcl Scripts

Information About Signed Tcl Scripts

Cisco IOS PKI

RSA Key Pair

Certificate and Trustpoint

How to Configure Signed Tcl Scripts

Generating a Key Pair

Generating a Certificate

Signing the Tcl Scripts

Verifying the Signature

Converting the Signature into Nonbinary Data

Configuring the Router with a Certificate

Verifying the Trustpoint

Verifying the Signed Tcl Script

What to Do Next

Configuration Examples for Signed Tcl Script

Generating a Key Pair: Example

Generating a Certificate: Example

Signing the Tcl Scripts: Example

Verifying the Signature: Example

Converting the Signature with Nonbinary Data: Example

Configuring the Router with a Certificate: Example

Additional References

Related Documents

Standards

MIBs

RFCs

Technical Assistance

Command Reference

scripting tcl secure-mode

scripting tcl trustpoint name

scripting tcl trustpoint untrusted

tclsafe

Feature Information for Signed Tcl Scripts

Glossary

Signed Tcl Scripts

First Published: July 19, 2007

Last Update: November 30, 2007

The Signed Tcl Scripts feature allows you to create a certificate to generate a digital signature and sign a Tool Command Language (Tcl) script with that digital signature. This feature also allows you to work with existing scripts and certificates. The digital signature is verified for authentication and then run with trusted access to the Tcl interpreter. If the script does not contain the digital signature, the script may run in a limited mode for untrusted scripts, or may not run at all.

Finding Feature Information in This Module

Your Cisco IOS software release may not support all of the features documented in this module. To reach links to specific feature documentation in this module and to see a list of the releases in which each feature is supported, use the "Feature Information for Signed Tcl Scripts" section.

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Contents

•Prerequisites for Signed Tcl Scripts

•Restrictions for Signed Tcl Scripts

•Information About Signed Tcl Scripts

•How to Configure Signed Tcl Scripts

•Configuration Examples for Signed Tcl Script

•Additional References

•Command Reference

•Feature Information for Signed Tcl Scripts

•Glossary

Prerequisites for Signed Tcl Scripts

For this feature to work, the Cisco IOS public key infrastructure (PKI) configuration trustpoint commands must be enabled.

For further details, see the "Related Documents" section.

Restrictions for Signed Tcl Scripts

For this feature to work, you must be running the following:

•Cisco IOS Crypto image

•OpenSSL Version 0.9.7a or above

•Expect

Information About Signed Tcl Scripts

The Signed Tcl Scripts feature introduces security for the Tcl scripts. This feature allows you to create a certificate to generate a digital signature and sign a Tcl script with that digital signature. This certificate examines the Tcl scripts prior to running them. The script is checked for a digital signature from Cisco. In addition, third parties may also sign a script with a digital signature. You may wish to sign your own internally developed Tcl scripts or you could use a script developed by a third party. If the script contains the correct digital signature, it is believed to be authentic and runs with full access to the Tcl interpreter. If the script does not contain the digital signature, the script may be run in a limited mode, known as Safe Tcl mode, or may not run at all.

To create and use signed Tcl scripts, you should understand the following concepts:

•Cisco IOS PKI

•RSA Key Pair

•Certificate and Trustpoint

Cisco IOS PKI

Cisco IOS PKI provides certificate management to support security protocols such as IP security (IPsec), secure shell (SSH), and secure socket layer (SSL). A PKI is composed of the following entities:

•Peers communicating on a secure network

•At least one certification authority (CA) that grants and maintains certificates

•Digital certificates, which contain information such as the certificate validity period, peer identity information, encryption keys that are used for secure communication, and the signature of the issuing CA

•An optional registration authority (RA) to offload the CA by processing enrollment requests

•A distribution mechanism (such as Lightweight Directory Access Protocol [LDAP] or HTTP) for certificate revocation lists (CRLs)

PKI provides you with a scalable, secure mechanism for distributing, managing, and revoking encryption and identity information in a secured data network. Every routing device participating in the secured communication is enrolled in the PKI in a process where the routing device generates a Rivest, Shamir, and Adelman (RSA) key pair (one private key and one public key) and has its identity validated by a trusted routing device (also known as a CA or trustpoint).

After each routing device enrolls in a PKI, every peer (also known as an end host) in a PKI is granted a digital certificate that has been issued by a CA. When peers must negotiate a secured communication session, they exchange digital certificates. Based on the information in the certificate, a peer can validate the identity of another peer and establish an encrypted session with the public keys contained in the certificate.

RSA Key Pair

An RSA key pair consists of a public key and a private key. When setting up your PKI, you must include the public key in the certificate enrollment request. After the certificate has been granted, the public key is included in the certificate so that peers can use it to encrypt data that is sent to the router. The private key is kept on the router and used both to decrypt the data sent by peers and to digitally sign transactions when negotiating with peers.

RSA key pairs contain a key modulus value. The modulus determines the size of the RSA key. The larger the modulus, the more secure the RSA key. However, keys with large modulus values take longer to generate, and encryption and decryption operations take longer with larger keys.

Certificate and Trustpoint

A certification authority (CA), also known as a trustpoint, manages certificate requests and issues certificates to participating network devices. These services (managing certificate requests and issuing certificates) provide centralized key management for the participating devices and are explicitly trusted by the receiver to validate identities and to create digital certificates. Before any PKI operations can begin, the CA generates its own public key pair and creates a self-signed CA certificate; thereafter, the CA can sign certificate requests and begin peer enrollment for the PKI.

You can use a CA provided by a third-party CA vendor, or you can use an internal CA, which is the Cisco IOS Certificate Server.

How to Configure Signed Tcl Scripts

This section contains the following tasks:

•Generating a Key Pair (required)

•Generating a Certificate (required)

•Signing the Tcl Scripts (required)

•Verifying the Signature (required)

•Converting the Signature into Nonbinary Data (required)

•Configuring the Router with a Certificate (required)

•Verifying the Trustpoint (optional)

•Verifying the Signed Tcl Script (optional)

•What to Do Next

Generating a Key Pair

The key pair consists of a private key and a public key. The private key is intended to be kept private, accessible only to the creator. The public key is generated from the private key and is intended to be known to the public.

To generate a key pair, use the openssl genrsa command and then the openssl rsa command.

SUMMARY STEPS

1. openssl genrsa -out private-key-file bit-length

2. ls -l

3. openssl rsa -in private-key-file -pubout -out public-key-file

4. ls -l

DETAILED STEPS

Step 1 openssl genrsa -out private-key-file bit-length

This command generates a private key that is bit-length bits long and writes the key to the private-key-file file.

Host% openssl genrsa -out privkey.pem 2048
Generating RSA private key, 2048 bit long modulus
.........+++
...............................................................................+++
e is 65537 (0x10001)
Step 2 ls -l

This command displays detailed information about each file in the current directory, including the permissions, owners, size, and when last modified.
Host% ls -l 
total 8
-rw-r--r--   1 janedoe eng12       1679 Jun 12 14:55 privkey.pem
The privkey.pem file contains the private key generated using the openssl genrsa command.

Step 3 openssl rsa -in private-key-file -pubout -out public-key-file

This command generates a public key based on the specified private key in the private-key-file file and writes the public key to the public-key-file file.
Host% openssl rsa -in privkey.pem -pubout -out pubkey.pem 
writing RSA key
Step 4 ls -l

This command displays detailed information about each file in the current directory, including the permissions, owners, size, and when last modified.
Host% ls -l 
total 16
-rw-r--r--   1 janedoe eng12       1679 Jun 12 14:55 privkey.pem
-rw-r--r--   1 janedoe eng12        451 Jun 12 14:57 pubkey.pem
The pubkey.pem file contains the public key generated from the private key using the openssl rsa command.

Generating a Certificate

Perform this task to generate a certificate. To generate an X.509 certificate, use the openssl req command.

SUMMARY STEPS

1. openssl req -new -x509 -key private-key-file -out certificate-file -days number

2. ls -l

DETAILED STEPS

Step 1 openssl req -new -x509 -key private-key-file -out certificate-file -days expiration-days

This command creates an X.509 certificate, with full access to a private key that is stored in the private-key-file file, and stores the certificate in the certificate-file file. The certificate is configured to expire in expiration-days days.

To complete the command, enter the following Distinguished Name (DN) information when prompted:

•Country name

•State or province name

•Organization name

•Organizational unit name

•Common name

•Email address

At each prompt, text enclosed in square brackets indicates the default value that will be used if you do not enter a value before you press Enter.

This example shows how to create an X.509 certificate that has full access to the private key in the privkey.pem file. The certificate is written to the cert.pem file and will expire 1095 days after the creation date.
Host% openssl req -new -x509 -key privkey.pem -out cert.pem -days 1095 
You are about to be asked to enter information that will be incorporated
into your certificate request.
What you are about to enter is what is called a Distinguished Name or a DN.
There are quite a few fields but you can leave some blank
For some fields there will be a default value, If you enter '.', the field will be left 
blank.
-----
Country Name (2 letter code) [GB]:US 
State or Province Name (full name) [Berkshire]:California 
Locality Name (eg, city) [Newbury]:San Jose 
Organization Name (eg, company) [My Company Ltd]:Cisco Systems, Inc. 
Organizational Unit Name (eg, section) []:DEPT_ACCT 
Common Name (eg, your name or your server's hostname) []:Jane 
Email Address []:janedoe@company.com 
Step 2 ls -l

This command displays detailed information about each file in the current directory, including the permissions, owners, size, and when last modified.
Host% ls -l 
total 24
-rw-r--r--   1 janedoe eng12       1659 Jun 12 15:01 cert.pem
-rw-r--r--   1 janedoe eng12       1679 Jun 12 14:55 privkey.pem
-rw-r--r--   1 janedoe eng12        451 Jun 12 14:57 pubkey.pem
The cert.pem file contains the X.509 certificate created using the openssl req command.

Signing the Tcl Scripts

Perform this task to sign the Tcl scripts. You will need to sign the Tcl file and output in OpenSSL document in pkcs7 (PKCS#7) format.

To sign the Tcl file, use the openssl smime command with the -sign keyword.

SUMMARY STEPS

1. openssl smime -sign -in tcl-file -out signed-message-file -signer certificate-file -inkey private-key-file -outform DER -binary

2. ls -l

DETAILED STEPS

Step 1 openssl smime -sign -in tcl-file -out signed-tcl-file -signer certificate-file -inkey private-key-file -outform DER -binary

This command signs the Tcl filename tcl-file using the certificate stored in certificate-file and the private key stored in private-key-file file and then writes the signed Tcl file in DER PKCS#7 format to the signed-tcl-file file.
Host% openssl smime -sign -in hello -out hello.pk7 -signer cert.pem -inkey privkey.pem 
-outform DER -binary
Step 2 ls -l

This command displays detailed information about each file in the current directory, including the permissions, owners, size, and when last modified.
Host% ls -l 
total 40
-rw-r--r--   1 janedoe eng12       1659 Jun 12 15:01 cert.pem
-rw-r--r--   1 janedoe eng12        115 Jun 13 10:16 hello
-rw-r--r--   1 janedoe eng12       1876 Jun 13 10:16 hello.pk7
-rw-r--r--   1 janedoe eng12       1679 Jun 12 14:55 privkey.pem
-rw-r--r--   1 janedoe eng12        451 Jun 12 14:57 pubkey.pem
The hello.pk7 file contains the signed Tcl file created by the openssl smime command from the unsigned Tcl file named hello and using the X.509 certificate in the cert.pem file.

Verifying the Signature

Perform this task to verify that the signature matches the data, use the openssl smime command with the -verify keyword. The original Tcl content must be provided in the input file, because the file does not have the original content.

SUMMARY STEPS

1. openssl smime -verify -in signed-tcl-file -CAfile certificate-file -inform DER -content tcl-file

2. ls -l

DETAILED STEPS

Step 1 openssl smime -verify -in signed-tcl-file -CAfile certificate-file -inform DER -content tcl-file

This command verifies the signed Tcl file stored in DER PKCS#7 format in signed-tcl-file using the trusted Certificate Authority (CA) certificates in certificate-file and then writes the detached content to the file tcl-file.

The following example shows how to verify the signature with the input file hello.pk7:
Host% openssl smime -verify -in hello.pk7 -CAfile cert.pem -inform DER -content hello 
puts hello
puts "argc = $argc"
puts "argv = $argv"
puts "argv0 = $argv0"
puts "tcl_interactive = $tcl_interactive"
Verification successful
Note The SSL command page describes -in filename as the input message to be encrypted or signed or the MIME message to be decrypted or verified. For more information, go to http://www.openssl.org/.

Step 2 ls -l

This command displays detailed information about each file in the current directory, including the permissions, owners, size, and when last modified.
Host% ls -l 
total 40
-rw-r--r--   1 janedoe eng12       1659 Jun 13 10:18 cert.pem
-rw-r--r--   1 janedoe eng12        115 Jun 13 10:17 hello
-rw-r--r--   1 janedoe eng12       1876 Jun 13 10:16 hello.pk7
-rw-r--r--   1 janedoe eng12       1679 Jun 12 14:55 privkey.pem
-rw-r--r--   1 janedoe eng12        451 Jun 12 14:57 pubkey.pem
The hello file contains the content detached from the signed Tcl file hello.pk7 by running the openssl smime command with the -verify keyword. If the verification was successful, the signer's certificates are written to the X.509 certificate in the cert.pem file.

Converting the Signature into Nonbinary Data

Perform this task to convert the signature from binary to nonbinary data.

SUMMARY STEPS

1. xxd -ps signed-tcl-file > nonbinary-signature-file

2. Create a script that will display #Cisco Tcl Signature V1.0 then insert the comment character # at the beginning of each line of the input file.

3. Run the script, supplying the name of the file containing the nonbinary signature file (nonbinary-signature-file file) as the input argument.

4. ls -l

5. cat signed-tcl-file commented-nonbinary-signature-file > signed-tcl-script

6. cat signed-tcl-script

DETAILED STEPS

Step 1 xxd -ps signed-tcl-file > nonbinary-signature-file

This command converts the signature in signed-tcl-file from binary to nonbinary data and stores it as a hexadecimal dump in the file nonbinary-signature-file.
Host% xxd -ps hello.pk7 > hello.hex 
Step 2 Create a script that displays #Cisco Tcl Signature V1.0 in the first line and inserts a comment character (#) at the beginning of each line of the input file and writes each line to a file whose name is formed by appending the text string "_sig" to the name of the input file.

In this example the cat command is used to display the contents of the script file named my_append.
Host% cat my_append 
#!/usr/bin/env expect
set my_first {#Cisco Tcl Signature V1.0}
set newline {}
set my_file [lindex $argv 0]
set my_new_file ${my_file}_sig
set my_new_handle [open $my_new_file w]
set my_handle [open $my_file r]
puts $my_new_handle $newline
puts $my_new_handle $my_first
foreach line [split [read $my_handle] "\n"]  {
   set new_line {#}
   append new_line $line
   puts $my_new_handle $new_line
}
close $my_new_handle
close $my_handle
Step 3 Run the script, supplying the name of the file containing the nonbinary signature file (nonbinary-signature-file) as the input argument.

In this example, the my_append script is run with the nonbinary signature file hello.hex specified as input. The output file will be named hello.hex_sig.
Host% my_append hello.hex 
Step 4 ls -l

This command displays detailed information about each file in the current directory, including the permissions, owners, size, and when last modified.
Host% ls -l 
total 80
-rw-r--r--   1 janedoe eng12       1659 Jun 13 10:18 cert.pem
-rw-r--r--   1 janedoe eng12        115 Jun 13 10:17 hello
-rw-r--r--   1 janedoe eng12       3815 Jun 13 10:20 hello.hex
-rw-r--r--   1 janedoe eng12       3907 Jun 13 10:22 hello.hex_sig
-rw-r--r--   1 janedoe eng12       1876 Jun 13 10:16 hello.pk7
-rwxr--r--   1 janedoe eng12        444 Jun 13 10:22 my_append
-rw-r--r--   1 janedoe eng12       1679 Jun 12 14:55 privkey.pem
-rw-r--r--   1 janedoe eng12        451 Jun 12 14:57 pubkey.pem
The hello.hex file contains nonbinary data (stored as a hexadecimal dump) converted from the binary signature in the signed Tcl file hello.pk7. The my_append file contains the script that inserts a comment character at the beginning of each line of the input file. The hello.hex_sig file is the file created by running the my_append script on the nonbinary signature file.

Step 5 cat signed-tcl-file commented-nonbinary-signature-file > signed-tcl-script

This command appends the contents of the nonbinary signature file (commented-nonbinary-signature-file) to the signed Tcl file stored in DER PKCS#7 format (in the signed-tcl-file file). The concatenated output is written to the file signed-tcl-script.
Host% cat hello hello.hex_sig > hello.tcl 
Step 6 cat signed-tcl-script

This command displays the contents of the file signed-tcl-script, which is the concatenation of content detached from the signed Tcl file and the nonbinary signature file.
Host% cat hello.tcl 
puts hello
puts "argc = $argc"
puts "argv = $argv"
puts "argv0 = $argv0"
puts "tcl_interactive = $tcl_interactive"
#Cisco Tcl Signature V1.0
#3082075006092a864886f70d010702a08207413082073d020101310b3009
#06052b0e03021a0500300b06092a864886f70d010701a08204a13082049d
#30820385a003020102020100300d06092a864886f70d0101040500308195
#310b3009060355040613025553311330110603550408130a43616c69666f
#726e69613111300f0603550407130853616e204a6f7365311c301a060355
#040a1313436973636f2053797374656d732c20496e632e310e300c060355
#040b13054e53535447310d300b060355040313044a6f686e3121301f0609
#2a864886f70d01090116126a6c6175746d616e40636973636f2e636f6d30
#1e170d3037303631323232303134335a170d313030363131323230313433
#5a308195310b3009060355040613025553311330110603550408130a4361
#6c69666f726e69613111300f0603550407130853616e204a6f7365311c30
#1a060355040a1313436973636f2053797374656d732c20496e632e310e30
#0c060355040b13054e53535447310d300b060355040313044a6f686e3121
#301f06092a864886f70d01090116126a6c6175746d616e40636973636f2e
#636f6d30820122300d06092a864886f70d01010105000382010f00308201
#0a0282010100a751eb5ec1f3009738c88a55987c07b759c36f3386342283
#67ea20a89d9483ae85e0c63eeded8ab3eb7a08006689f09136f172183665
#c971099ba54e77ab47706069bbefaaab8c50184396350e4cc870c4c3f477
#88c55c52e2cf411f05b59f0eaec0678ff5cc238fdce2263a9fc6b6c244b8
#ffaead865c19c3d3172674a13b24c8f2c01dd8b1bd491c13e84e29171b85
#f28155d81ac8c69bb25ca23c2921d85fbf745c106e7aff93c72316cbc654
#4a34ea88174a8ba7777fa60662974e1fbac85a0f0aeac925dba6e5e850b8
#7caffce2fe8bb04b61b62f532b5893c081522d538005df81670b931b0ad0
#e1e76ae648f598a9442d5d0976e67c8d55889299147d0203010001a381f5
#3081f2301d0603551d0e04160414bc34132be952ff8b9e1af3b93140a255
#e54a667c3081c20603551d230481ba3081b78014bc34132be952ff8b9e1a
#f3b93140a255e54a667ca1819ba48198308195310b300906035504061302
#5553311330110603550408130a43616c69666f726e69613111300f060355
#0407130853616e204a6f7365311c301a060355040a1313436973636f2053
#797374656d732c20496e632e310e300c060355040b13054e53535447310d
#300b060355040313044a6f686e3121301f06092a864886f70d0109011612
#6a6c6175746d616e40636973636f2e636f6d820100300c0603551d130405
#30030101ff300d06092a864886f70d010104050003820101000c83c1b074
#6720929c9514af6d5df96f0a95639f047c40a607c83d8362507c58fa7f84
#aa699ec5e5bef61b2308297a0662c653ff446acfbb6f5cb2dd162d939338
#a5e4d78a5c45021e5d4dbabb8784efbf50cab0f5125d164487b31f5cf933
#a9f68f82cd111cbab1739d7f372ec460a7946882874b0a0f22dd53acbd62
#a944a15e52e54a24341b3b8a820f23a5bc7ea7b2278bb56838b8a4051926
#af9c167274ff8449003a4e012bcf4f4b3e280f85209249a390d14df47435
#35efabce720ea3d56803a84a2163db4478ae19d7d987ef6971c8312e280a
#aac0217d4fe620c6582a48faa8ea5e3726a99012e1d55f8d61b066381f77
#4158d144a43fb536c77d6a318202773082027302010130819b308195310b
#3009060355040613025553311330110603550408130a43616c69666f726e
#69613111300f0603550407130853616e204a6f7365311c301a060355040a
#1313436973636f2053797374656d732c20496e632e310e300c060355040b
#13054e53535447310d300b060355040313044a6f686e3121301f06092a86
#4886f70d01090116126a6c6175746d616e40636973636f2e636f6d020100
#300906052b0e03021a0500a081b1301806092a864886f70d010903310b06
#092a864886f70d010701301c06092a864886f70d010905310f170d303730
#3631333137313634385a302306092a864886f70d01090431160414372cb3
#72dc607990577fd0426104a42ee4158d2b305206092a864886f70d01090f
#31453043300a06082a864886f70d0307300e06082a864886f70d03020202
#0080300d06082a864886f70d0302020140300706052b0e030207300d0608
#2a864886f70d0302020128300d06092a864886f70d010101050004820100
#72db6898742f449b26d3ac18f43a1e7178834fb05ad13951bf042e127eea
#944b72b96f3b8ecf7eb52f3d0e383bf63651750223efe69eae04287c9dae
#b1f31209444108b31d34e46654c6c3cc10b5baba887825c224ec6f376d49
#00ff7ab2d9f88402dab9a2c2ab6aa3ecceeaf5a594bdc7d3a822c55e7daa
#aa0c2b067e06967f22a20e406fe21d9013ecc6bd9cd6d402c2749f8bea61
#9f8f87acfbc9e10d6ce91502e34629adca6ee855419afafe6a8233333e14
#ad4c107901d1f2bca4d7ffaadddbc54192a25da662f8b8509782c76977b8
#94879453fbb00486ccc55f88db50fcc149bae066916b350089cde51a6483
#2ec14019611720fc5bbe2400f24225fc
Configuring the Router with a Certificate

Perform this task to configure the router with a certificate.

Prerequisites

You must already have a Cisco IOS Crypto image; otherwise you cannot configure a certificate.

SUMMARY STEPS

1. enable

2. configure terminal

3. crypto pki trustpoint name

4. enrollment terminal

5. exit

6. crypto pki authenticate name

7. Enter the base-encoded CA certificate.

8. scripting tcl secure-mode

9. scripting tcl trustpoint name name

10. (Optional) scripting tcl trustpoint untrusted {execute| safe-execute | terminate}

11. exit

12. (Optional) tclsafe

DETAILED STEPS

Step 1 enable

Enables privileged EXEC mode. Enter your password if prompted.
Router> enable
Step 2 configure terminal

Enters global configuration mode.
Router# configure terminal
Step 3 crypto pki trustpoint name

Declares the router is to use the Certificate Authority (CA) mytrust and enters ca-trustpoint configuration mode.
Router(config)# crypto pki trustpoint mytrust 
Step 4 enrollment terminal

Specifies manual cut-and-paste certificate enrollment. When this command is enabled, the router displays the certificate request on the console terminal, allowing you to enter the issued certificate on the terminal.
Router(ca-trustpoint)# enrollment terminal 
Step 5 exit

Exits ca-trustpoint configuration mode and returns to global configuration mode.
Router(ca-trustpoint)# exit
Step 6 crypto pki authenticate name

Retrieves the CA certificate and authenticates it. Check the certificate fingerprint if prompted.

Note Because the CA signs its own certificate, you should manually authenticate the public key of the CA by contacting the CA administrator when you perform this command.
Router(config)# crypto pki authenticate mytrust 
Step 7 At the prompt, enter the base-encoded CA certificate.
Enter the base 64 encoded CA certificate.
End with a blank line or the word "quit" on a line by itself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Certificate has the following attributes:
       Fingerprint MD5: 1E327DBB 330936EB 2FB8EACB 4FD1133E 
      Fingerprint SHA1: EE7FF9F4 05148842 B9D50FAC D76FDC9C E0703246 
% Do you accept this certificate? [yes/no]: yes
Trustpoint CA certificate accepted.
% Certificate successfully imported
Step 8 scripting tcl secure-mode

Enables signature verification of the interactive Tcl scripts.

Router(config)# scripting tcl secure-mode
Step 9 scripting tcl trustpoint name name

Associates an existing configured trustpoint name with a certificate to verify Tcl scripts.

Router(config)# scripting tcl trustpoint name mytrust
Step 10 scripting tcl trustpoint untrusted {execute | safe-execute | terminate}

(Optional) Allows the interactive Tcl scripts to run regardless of the scripts failing in the signature check or in untrusted mode using one of the three keywords: execute, safe-execute, or terminate.

•execute—Executes Tcl scripts even if the signature verification fails. If the execute keyword is configured, signature verification is not at all performed.

Note Use of this keyword is usually not recommended because the signature verification is not at all performed.

The execute keyword is provided for internal testing purposes and to provide flexibility. For example, in a situation where a certificate has expired but the other configurations are valid and you want to work with the existing configuration, then you can use the execute keyword to work around the expired certificate.

•safe-execute—Allows the script to run in safe mode. You can use the tclsafe command and also enter the interactive Tcl shell safe mode to explore the safe mode Tcl commands that are available. In order to get a better understanding of what is available in this limited safe mode, use the tclsafe Exec command to explore the options.

•terminate—Stops any script from running and reverts to default behavior. The default policy is to terminate. When the last trustpoint name is removed, the untrusted action is also removed. The untrusted action cannot be entered until at least one trustpoint name is configured for Tcl.

The following example shows how to execute the Tcl script in safe mode using the safe-execute keyword when the signature verification fails.

Router(config)# scripting tcl trustpoint untrusted safe-execute
Step 11 exit

Exits global configuration mode and returns to privileged EXEC mode.

Router(config)# exit
Step 12 tclsafe

(Optional) Enables the interactive Tcl shell untrusted safe mode. This allows you to manually run Tcl commands from the Cisco IOS command-line interface (CLI) in untrusted safe mode.

Router# tclsafe
Verifying the Trustpoint

To display the trustpoints that are configured in the router, use the show crypto pki trustpoints command.

SUMMARY STEPS

1. enable

2. show crypto pki trustpoints

DETAILED STEPS

Step 1 enable

This command enables privileged EXEC mode.
Router> enable 
Step 2 show crypto pki trustpoints

This command displays the trustpoints that are configured in the router.
Router# show crypto pki trustpoints 
Trustpoint mytrust:
    Subject Name: 
    ea=janedoe@cisco.com
    cn=Jane
    ou=DEPT_ACCT
    o=Cisco
    l=San Jose
    st=California
    c=US
          Serial Number: 00
    Certificate configured.
Verifying the Signed Tcl Script

To verify that the Signed Tcl Script is properly running, use the debug crypto pki transactions command and the tclsh flash command.

SUMMARY STEPS

1. enable

2. debug crypto pki transactions

3. tclsh flash:signed-tcl-file

DETAILED STEPS

Step 1 enable

This command enables privileged EXEC mode.
Router> enable 
Step 2 debug crypto pki transactions

This command display debugging messages for the trace of interaction (message type) between the CA and the router.
Router# debug crypto pki transactions 
Crypto PKI Trans debugging is on 
Step 3 tclsh flash:signed-tcl-file

This command executes the Tcl script in Tcl shell.

Note The file should be a signed Tcl file.
Router# tclsh flash:hello.tcl 
hello
argc = 0
argv = 
argv0 = flash:hello.tcl
tcl_interactive = 0
Router#
*Apr 21 04:46:18.563: CRYPTO_PKI: locked trustpoint mytrust, refcount is 1
*Apr 21 04:46:18.563: The PKCS #7 message has 0 verified signers.
*Apr 21 04:46:18.563: CRYPTO_PKI: Success on PKCS7 verify!
*Apr 21 04:46:18.563: CRYPTO_PKI: unlocked trustpoint mytrust, refcount is 0
What to Do Next

•To get an overview of Crypto, go to "Part 5: Implementing and Managing a PKI" section of the Cisco IOS Security Configuration Guide, Release 12.4T.

Configuration Examples for Signed Tcl Script

This section provided the following configuration examples:

•Generating a Key Pair: Example

•Generating a Certificate: Example

•Signing the Tcl Scripts: Example

•Verifying the Signature: Example

•Converting the Signature with Nonbinary Data: Example

•Configuring the Router with a Certificate: Example

Generating a Key Pair: Example

Generate a Private Key: Example
Host% openssl genrsa -out privkey.pem 2048
Generating RSA private key, 2048 bit long modulus
.........+++
...............................................................................+++
e is 65537 (0x10001)
Host% ls -l
total 8
-rw-r--r--   1 janedoe eng12       1679 Jun 12 14:55 privkey.pem
Host%
Generate a Public Key from the Private Key
Host% openssl rsa -in privkey.pem -pubout -out pubkey.pem
writing RSA key
Host% ls -l 
total 16
-rw-r--r--   1 janedoe eng12       1679 Jun 12 14:55 privkey.pem
-rw-r--r--   1 janedoe eng12        451 Jun 12 14:57 pubkey.pem
Generating a Certificate: Example
Host% openssl req -new -x509 -key privkey.pem -out cert.pem -days 1095
You are about to be asked to enter information that will be incorporated
into your certificate request.
What you are about to enter is what is called a Distinguished Name or a DN.
There are quite a few fields but you can leave some blank
For some fields there will be a default value, If you enter '.', the field will be left 
blank.
-----
Country Name (2 letter code) [GB]:US
State or Province Name (full name) [Berkshire]:California
Locality Name (eg, city) [Newbury]:San Jose
Organization Name (eg, company) [My Company Ltd]:Cisco Systems, Inc.
Organizational Unit Name (eg, section) []:DEPT_ACCT
Common Name (eg, your name or your server's hostname) []:Jane
Email Address []:janedoe@company.com
Host% ls -l
total 24
-rw-r--r--   1 janedoe eng12       1659 Jun 12 15:01 cert.pem
-rw-r--r--   1 janedoe eng12       1679 Jun 12 14:55 privkey.pem
-rw-r--r--   1 janedoe eng12        451 Jun 12 14:57 pubkey.pem
Signing the Tcl Scripts: Example
Host% openssl smime -sign -in hello -out hello.pk7 -signer cert.pem -inkey privkey.pem 
-outform DER -binary
Host% ls -l
total 40
-rw-r--r--   1 janedoe eng12       1659 Jun 12 15:01 cert.pem
-rw-r--r--   1 janedoe eng12        115 Jun 13 10:16 hello
-rw-r--r--   1 janedoe eng12       1876 Jun 13 10:16 hello.pk7
-rw-r--r--   1 janedoe eng12       1679 Jun 12 14:55 privkey.pem
-rw-r--r--   1 janedoe eng12        451 Jun 12 14:57 pubkey.pem
Verifying the Signature: Example
Host% openssl smime -verify -in hello.pk7 -CAfile cert.pem -inform DER -content hello
puts hello
puts "argc = $argc"
puts "argv = $argv"
puts "argv0 = $argv0"
puts "tcl_interactive = $tcl_interactive"
Verification successful
Converting the Signature with Nonbinary Data: Example
#Cisco Tcl Signature V1.0
Then append the signature file to the end of the file.
Host% xxd -ps hello.pk7 > hello.hex
Host% cat my_append
#!/usr/bin/env expect
set my_first {#Cisco Tcl Signature V1.0}
set newline {}
set my_file [lindex $argv 0]
set my_new_file ${my_file}_sig
set my_new_handle [open $my_new_file w]
set my_handle [open $my_file r]
puts $my_new_handle $newline
puts $my_new_handle $my_first
foreach line [split [read $my_handle] "\n"]  {
   set new_line {#}
   append new_line $line
   puts $my_new_handle $new_line
}
close $my_new_handle
close $my_handle
Host% my_append hello.hex
Host% ls -l
total 80
-rw-r--r--   1 janedoe eng12       1659 Jun 12 15:01 cert.pem
-rw-r--r--   1 janedoe eng12        115 Jun 13 10:16 hello
-rw-r--r--   1 janedoe eng12       3815 Jun 13 10:20 hello.hex
-rw-r--r--   1 janedoe eng12       3907 Jun 13 10:22 hello.hex_sig
-rw-r--r--   1 janedoe eng12       1876 Jun 13 10:16 hello.pk7
-rwxr--r--   1 janedoe eng12        444 Jun 13 10:22 my_append
-rw-r--r--   1 janedoe eng12       1679 Jun 12 14:55 privkey.pem
-rw-r--r--   1 janedoe eng12        451 Jun 12 14:57 pubkey.pem
Host% cat hello hello.hex_sig > hello.tcl
Host% cat hello.tcl
puts hello
puts "argc = $argc"
puts "argv = $argv"
puts "argv0 = $argv0"
puts "tcl_interactive = $tcl_interactive"
#Cisco Tcl Signature V1.0
#3082075006092a864886f70d010702a08207413082073d020101310b3009
#06052b0e03021a0500300b06092a864886f70d010701a08204a13082049d
#30820385a003020102020100300d06092a864886f70d0101040500308195
#310b3009060355040613025553311330110603550408130a43616c69666f
#726e69613111300f0603550407130853616e204a6f7365311c301a060355
#040a1313436973636f2053797374656d732c20496e632e310e300c060355
#040b13054e53535447310d300b060355040313044a6f686e3121301f0609
#2a864886f70d01090116126a6c6175746d616e40636973636f2e636f6d30
#1e170d3037303631323232303134335a170d313030363131323230313433
#5a308195310b3009060355040613025553311330110603550408130a4361
#6c69666f726e69613111300f0603550407130853616e204a6f7365311c30
#1a060355040a1313436973636f2053797374656d732c20496e632e310e30
#0c060355040b13054e53535447310d300b060355040313044a6f686e3121
#301f06092a864886f70d01090116126a6c6175746d616e40636973636f2e
#636f6d30820122300d06092a864886f70d01010105000382010f00308201
#0a0282010100a751eb5ec1f3009738c88a55987c07b759c36f3386342283
#67ea20a89d9483ae85e0c63eeded8ab3eb7a08006689f09136f172183665
#c971099ba54e77ab47706069bbefaaab8c50184396350e4cc870c4c3f477
#88c55c52e2cf411f05b59f0eaec0678ff5cc238fdce2263a9fc6b6c244b8
#ffaead865c19c3d3172674a13b24c8f2c01dd8b1bd491c13e84e29171b85
#f28155d81ac8c69bb25ca23c2921d85fbf745c106e7aff93c72316cbc654
#4a34ea88174a8ba7777fa60662974e1fbac85a0f0aeac925dba6e5e850b8
#7caffce2fe8bb04b61b62f532b5893c081522d538005df81670b931b0ad0
#e1e76ae648f598a9442d5d0976e67c8d55889299147d0203010001a381f5
#3081f2301d0603551d0e04160414bc34132be952ff8b9e1af3b93140a255
#e54a667c3081c20603551d230481ba3081b78014bc34132be952ff8b9e1a
#f3b93140a255e54a667ca1819ba48198308195310b300906035504061302
#5553311330110603550408130a43616c69666f726e69613111300f060355
#0407130853616e204a6f7365311c301a060355040a1313436973636f2053
#797374656d732c20496e632e310e300c060355040b13054e53535447310d
#300b060355040313044a6f686e3121301f06092a864886f70d0109011612
#6a6c6175746d616e40636973636f2e636f6d820100300c0603551d130405
#30030101ff300d06092a864886f70d010104050003820101000c83c1b074
#6720929c9514af6d5df96f0a95639f047c40a607c83d8362507c58fa7f84
#aa699ec5e5bef61b2308297a0662c653ff446acfbb6f5cb2dd162d939338
#a5e4d78a5c45021e5d4dbabb8784efbf50cab0f5125d164487b31f5cf933
#a9f68f82cd111cbab1739d7f372ec460a7946882874b0a0f22dd53acbd62
#a944a15e52e54a24341b3b8a820f23a5bc7ea7b2278bb56838b8a4051926
#af9c167274ff8449003a4e012bcf4f4b3e280f85209249a390d14df47435
#35efabce720ea3d56803a84a2163db4478ae19d7d987ef6971c8312e280a
#aac0217d4fe620c6582a48faa8ea5e3726a99012e1d55f8d61b066381f77
#4158d144a43fb536c77d6a318202773082027302010130819b308195310b
#3009060355040613025553311330110603550408130a43616c69666f726e
#69613111300f0603550407130853616e204a6f7365311c301a060355040a
#1313436973636f2053797374656d732c20496e632e310e300c060355040b
#13054e53535447310d300b060355040313044a6f686e3121301f06092a86
#4886f70d01090116126a6c6175746d616e40636973636f2e636f6d020100
#300906052b0e03021a0500a081b1301806092a864886f70d010903310b06
#092a864886f70d010701301c06092a864886f70d010905310f170d303730
#3631333137313634385a302306092a864886f70d01090431160414372cb3
#72dc607990577fd0426104a42ee4158d2b305206092a864886f70d01090f
#31453043300a06082a864886f70d0307300e06082a864886f70d03020202
#0080300d06082a864886f70d0302020140300706052b0e030207300d0608
#2a864886f70d0302020128300d06092a864886f70d010101050004820100
#72db6898742f449b26d3ac18f43a1e7178834fb05ad13951bf042e127eea
#944b72b96f3b8ecf7eb52f3d0e383bf63651750223efe69eae04287c9dae
#b1f31209444108b31d34e46654c6c3cc10b5baba887825c224ec6f376d49
#00ff7ab2d9f88402dab9a2c2ab6aa3ecceeaf5a594bdc7d3a822c55e7daa
#aa0c2b067e06967f22a20e406fe21d9013ecc6bd9cd6d402c2749f8bea61
#9f8f87acfbc9e10d6ce91502e34629adca6ee855419afafe6a8233333e14
#ad4c107901d1f2bca4d7ffaadddbc54192a25da662f8b8509782c76977b8
#94879453fbb00486ccc55f88db50fcc149bae066916b350089cde51a6483
#2ec14019611720fc5bbe2400f24225fc
Configuring the Router with a Certificate: Example
crypto pki trustpoint mytrust
 enrollment terminal
!
!
crypto pki authentication mytrust
crypto pki certificate chain mytrust
 certificate ca 00
  308204B8 308203A0 A0030201 02020100 300D0609 2A864886 F70D0101 04050030 
  819E310B 30090603 55040613 02555331 13301106 03550408 130A4361 6C69666F 
  726E6961 3111300F 06035504 07130853 616E204A 6F736531 1C301A06 0355040A 
  13134369 73636F20 53797374 656D732C 20496E63 2E310E30 0C060355 040B1305 
  4E535354 47311630 14060355 0403130D 4A6F686E 204C6175 746D616E 6E312130 
  1F06092A 864886F7 0D010901 16126A6C 6175746D 616E4063 6973636F 2E636F6D 
  301E170D 30363131 31373137 35383031 5A170D30 39313131 36313735 3830315A 
  30819E31 0B300906 03550406 13025553 31133011 06035504 08130A43 616C6966 
  6F726E69 61311130 0F060355 04071308 53616E20 4A6F7365 311C301A 06035504 
  0A131343 6973636F 20537973 74656D73 2C20496E 632E310E 300C0603 55040B13 
  054E5353 54473116 30140603 55040313 0D4A6F68 6E204C61 75746D61 6E6E3121 
  301F0609 2A864886 F70D0109 0116126A 6C617574 6D616E40 63697363 6F2E636F 
  6D308201 22300D06 092A8648 86F70D01 01010500 0382010F 00308201 0A028201 
  0100BC6D A933028A B31BF827 7258BB87 A1600CF0 21090F04 2080BECC 5818688B 
  74D231DF F0C365C1 07D6E206 D7651FA8 C7B230A2 3B0011E4 EA2B6A4C 1F3F27FB 
  9AF449D8 FA8900BB 3E567F77 5412881B AAD9525E 3EC1D3B1 EBCE8155 D74866F1 
  0940F6D1 3A2613CD F6B3595E F468B315 6DDEFF07 BBC5D521 B560AF72 D6D5FDA7 
  D9D9C99D 31E3B380 5DEB7039 A1A29EF9 46ED536E 4D768048 12D48C24 59B08973 
  481AD75D E741CD9E BE06EA16 9B514AE3 91184A56 A0E51B7D 4465D730 1AB3C7DD 
  62CA1AC9 DF30C39A 41316B8E 72289113 98080354 C7297AD7 89B627F8 ED40D924 
  ADF48383 1B332C7F 73C58686 6279E2A4 4BF41644 3E60F131 090D3F5D 25F0C025 
  43CB0203 010001A3 81FE3081 FB301D06 03551D0E 04160414 F7F4E80E F6CC4772 
  5F278C44 6B85F8EE 8345AB99 3081CB06 03551D23 0481C330 81C08014 F7F4E80E 
  F6CC4772 5F278C44 6B85F8EE 8345AB99 A181A4A4 81A13081 9E310B30 09060355 
  04061302 55533113 30110603 55040813 0A43616C 69666F72 6E696131 11300F06 
  03550407 13085361 6E204A6F 7365311C 301A0603 55040A13 13436973 636F2053 
  79737465 6D732C20 496E632E 310E300C 06035504 0B13054E 53535447 31163014 
  06035504 03130D4A 6F686E20 4C617574 6D616E6E 3121301F 06092A86 4886F70D 
  01090116 126A6C61 75746D61 6E406369 73636F2E 636F6D82 0100300C 0603551D 
  13040530 030101FF 300D0609 2A864886 F70D0101 04050003 82010100 6D12CFF8 
  31078DF6 94FE5CF0 8F83639B 414F32D8 069D23E2 37E182BE 7C31EC14 E87AF216 
  61A6CCD3 37656934 4BE4157A 400E182B EC390D1A DC130A56 B8F35BFB D2234556 
  24152FE8 A736B670 58CC684E 750D08AE C7739907 917B7A72 3D26BEC7 9F554CF1 
  5E5EF499 ABA11124 55966616 AC9C52B2 B1082DEA D962CBAF E476C575 A9DDFBFA 
  C4AE63F6 1D5C9F76 7B4B9CA7 52CE65C9 E65C04FC 4B7642D6 0D1A8AF4 38194B7A 
  CA307EC9 51DCB847 8B8C27FB 98ACEE60 0B80DC3F 36E4E252 BD731F5F 0E781E26 
  C1CA4120 9B0B689B BA654250 97B22A76 CC126B77 C7779AAA D3F93C3F DCF46006 
  2B7F7F8C 150AF889 BBEC62F1 E53B4F3B A3626CD6 05B8AB3D F8A6A361
   quit
archive
 log config
scripting tcl trustpoint name mytrust
scripting tcl secure-mode
!
!
end
Additional References

The following sections provide references related to the Signed Tcl Scripts feature.

Related Documents

Related Topic

Document Title

Cisco IOS PKI Overview: Understanding and Planning a PKI

Implementing and Managing a PKI

Cisco IOS Security Configuration Guide, Release 12.4

PKI commands: complete command syntax, command mode, command history, defaults, usage guidelines, and examples.

Cisco IOS Security Command Reference, Release 12.4

Standards

Standard

Title

None

—

MIBs

MIB

MIBs Link

None

To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:

http://www.cisco.com/go/mibs

RFCs

RFC

Title

None

—

Technical Assistance

Description

Link

The Cisco Support website provides extensive online resources, including documentation and tools for troubleshooting and resolving technical issues with Cisco products and technologies.

To receive security and technical information about your products, you can subscribe to various services, such as the Product Alert Tool (accessed from Field Notices), the Cisco Technical Services Newsletter, and Really Simple Syndication (RSS) Feeds.

Access to most tools on the Cisco Support website requires a Cisco.com user ID and password.

http://www.cisco.com/techsupport

Command Reference

This section documents only commands that are new.

•scripting tcl secure-mode

•scripting tcl trustpoint name

•scripting tcl trustpoint untrusted

•tclsafe

scripting tcl secure-mode

To enable signature verification of the interactive Tool Command Language (Tcl) scripts, use the scripting tcl secure-mode command in global configuration mode. To disable signature verification of the interactive Tcl scripts, use the no form of this command.

scripting tcl secure-mode
no scripting tcl secure-mode
Syntax Description

This command has no arguments or keywords.

Command Default

The signature verification of the interactive Tcl scripts is disabled.

Command Modes

Global configuration (config)

Command History

Release

Modification

12.4(15)T

This command was introduced.

Usage Guidelines

Use the scripting tcl secure-mode command to enable signature verification of all Tcl scripts run on the router. By default, the signature verification of the interactive Tcl scripts is disabled. You must enable the signature verification in order to verify whether the Tcl scripts match their digital signature. That would indicate they have not been altered since the digital signature was generated. If the script does not contain the digital signature, the script may run in a limited mode for untrusted script (that is, a script that has failed signature verification) or may not run at all. After receiving the results from the signature verification, the scripts are executed.

A Cisco IOS Crypto image software is required to enable this command and configure the Signed Tcl Scripts feature. The Crypto configuration commands enable the Cisco x.509 certificate storage. The scripting tcl secure-mode command can be enabled after the Crypto configuration trustpoint commands are enabled.

The scripting tcl trustpoint name command must be configured with the scripting tcl secure-mode command to verify the integrity of Tcl script signatures run on the router. Both commands must be configured to fully operate the feature; otherwise, a syslog message is generated:
*Jun 13 17:35:14.219: %SYS-6-SCRIPTING_TCL_INVALID_OR_MISSING_SIGNATURE: tcl signing 
validation failed on script signed with trustpoint name mytrust, cannot run the signed TCL 
script.
In addition, the crypto pki trustpoint name command provided should contain a certificate that matches the certificate that was originally used to generate the digital signature on the Tcl script.

Examples

The following example shows how to enable signature verification of the interactive Tcl scripts:
Router(config)# crypto pki trustpoint mytrust
Router(ca-trustpoint)# enrolment terminal
Router(ca-trustpoint)# exit
Router(config)# crypto pki authenticate mytrust
Enter the base 64 encoded CA certificate.
End with a blank line or the word "quit" on a line by itself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Certificate has the following attributes:
       Fingerprint MD5: 1E327DBB 330936EB 2FB8EACB 4FD1133E 
      Fingerprint SHA1: EE7FF9F4 05148842 B9D50FAC D76FDC9C E0703246 
% Do you accept this certificate? [yes/no]: yes
Trustpoint CA certificate accepted.
% Certificate successfully imported
Router(config)# scripting tcl secure-mode 
Router(config)# scripting tcl trustpoint name mytrust
Related Commands

Command

Description

scripting tcl trustpoint name

Associates an existing configured trustpoint name with a certificate to verify Tcl scripts.

scripting tcl trustpoint name

To associate an existing configured trustpoint name with a certificate to verify Tool Command Language (Tcl) scripts, use the scripting tcl trustpoint name command in global configuration mode. To remove an existing configured trustpoint name, use the no form of this command.

scripting tcl trustpoint name name
no scripting tcl trustpoint name name
Syntax Description

name

Name of the configured trustpoint name associated with a certificate. Only one name can be associated with one certificate.

Command Default

A trustpoint name is not associated with a certificate to verify the Tcl scripts.

Command Modes

Global configuration (config)

Command History

Release

Modification

12.4(15)T

This command was introduced.

Usage Guidelines

Use the scripting tcl trustpoint name command to associate an existing configured trustpoint name with a certificate to verify Tcl scripts. This way, Tcl identifies which certificate is used for verifying the Tcl scripts. The name must match an existing configured trustpoint name, otherwise, the command is rejected with an error message on the console. You can enter the command multiple times and configure multiple trustpoint names. Once you enter the command, you cannot modify the trustpoint name. However, you can remove the trustpoint name using the no form of the command. You must individually remove each name. When the last name is removed, no signature checking is performed, and the untrusted script (that is, a script that has failed signature verification) action configured by the scripting tcl trustpoint untrusted command is also removed.

A Cisco IOS Crypto image software is required to enable this command and configure the Signed Tcl Scripts feature. The Crypto configuration commands enable the Cisco x.509 certificate storage. The scripting tcl trustpoint name command can be enabled after the Crypto configuration trustpoint commands are enabled.

The scripting tcl secure-mode command must be configured with the scripting tcl trustpoint name command to verify the integrity of Tcl script signatures run on the router. Both commands must be configured to fully operate this feature; otherwise, a syslog message is generated:
*Jun 13 17:53:31.659: %SYS-6-SCRIPTING_TCL_SECURE_TRUSTPOINT: scripting tcl secure-mode is 
enabled, however no scripting tcl trustpoint names configured, cannot verify signed TCL 
script.
In addition, the crypto pki trustpoint name command provided should contain a certificate that matches the certificate that was originally used to generate the digital signature on the Tcl script.

Examples

The following example shows how the scripting tcl trustpoint name command is used to associate existing trustpoint names. Different names can be used for different departments with certificates:
Router(config)# crypto pki trustpoint mytrust
Router(ca-trustpoint)# enrolment terminal
Router(ca-trustpoint)# exit
Router(config)# crypto pki authenticate mytrust
Enter the base 64 encoded CA certificate.
End with a blank line or the word "quit" on a line by itself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Certificate has the following attributes:
       Fingerprint MD5: 1E327DBB 330936EB 2FB8EACB 4FD1133E 
      Fingerprint SHA1: EE7FF9F4 05148842 B9D50FAC D76FDC9C E0703246 
% Do you accept this certificate? [yes/no]: yes
Trustpoint CA certificate accepted.
% Certificate successfully imported
Router(config)# scripting tcl secure-mode 
Router(config)# scripting tcl trustpoint name mytrust
Router(config)# scripting tcl trustpoint name dept_accounting
Router(config)# scripting tcl trustpoint name dept_hr
Related Commands

Command

Description

scripting tcl secure-mode

Enables signature verification of the interactive Tcl scripts.

scripting tcl trustpoint untrusted

To allow the interactive Tool Command Language (Tcl) scripts to run regardless of the scripts failing the signature check, use the scripting tcl trustpoint untrusted command in global configuration mode. To disallow the interactive Tcl scripts to run regardless of the scripts failing the signature check, use the no form of this command.

scripting tcl trustpoint untrusted {execute | safe-execute | terminate}
no scripting tcl trustpoint untrusted
Syntax Description

execute

Executes Tcl scripts even if the signature verification fails.

Caution Use of this keyword is usually not recommended because the signature verification is not performed if the execute keyword is configured.

safe-execute

Executes the Tcl script in safe mode if the signature verification fails.

terminate

Does not run the Tcl script if the signature verification fails. The default keyword is terminate.

Command Default

No script that fails signature verification can run; the script immediately stops.

Command Modes

Global configuration (config)

Command History

Release

Modification

12.4(15)T

This command was introduced.

Usage Guidelines

Use the scripting tcl trustpoint untrusted command to allow the interactive Tcl scripts to run regardless of the scripts failing the signature check or in untrusted mode. The untrusted script (that is, a script that has failed signature verification) is not safe to use.

Caution Use of the execute keyword is usually not recommended because the signature verification is not performed.

The execute keyword is provided for internal testing purposes and to provide flexibility. For example in a situation where a certificate has expired but the other configurations are valid and you want to work with the existing configuration, then you can use the execute keyword to work around the expired certificate.

The safe-execute keyword allows the script to run in safe mode. You can use the tclsafe command and also enter the interactive Tcl shell safe mode to explore the safe mode Tcl commands that are available. In order to get a better understanding of what is available in this limited safe mode, use the tclsafe Exec command to explore the options.

The terminate keyword stops any script from running and reverts to default behavior. The default policy is to terminate. When the last trustpoint name is removed, the untrusted action is also removed. The untrusted action cannot be entered until at least one trustpoint name is configured for Tcl.

Note This command only applies to the Tcl shell; it does not impact other components that make use of Tcl. For example, Embedded Event Manager (EEM) cannot perform any signature checking.

Examples

The following example shows how to execute the Tcl script in safe mode if the signature verification fails:
Router(config)# scripting tcl trustpoint untrusted safe-execute
Related Commands

Command

Description

scripting tcl trustpoint name

Associates an existing configured trustpoint name with a certificate to verify Tcl scripts.

tclsafe

Enables the interactive Tcl shell untrusted safe mode.

tclsafe

To enable the interactive Tool Command Language (Tcl) shell untrusted safe mode, use the tclsafe command in privileged EXEC mode. To exit from the safe mode, use the exit or the tclquit command.

tclsafe
Syntax Description

This command has no arguments or keywords.

Command Default

The Tcl shell untrusted safe mode is disabled.

Command Modes

Privileged EXEC (#)

Command History

Release

Modification

12.4(15)T

This command was introduced.

Usage Guidelines

Use the tclsafe command when you want to manually run Tcl commands from the Cisco IOS command-line interface (CLI) in untrusted safe mode. When you use the tclsafe command and enter the interactive Tcl shell safe mode, you can explore the safe mode Tcl commands that are available. When a script fails the signature check for a configured trustpoint name, it is determined to be untrusted. Untrusted Tcl scripts execute in limited safe mode, if scripting tcl trustpoint untrusted safe-execute command is configured. In order to get a better understanding of what is available in this limited safe mode, use the tclsafe Exec command to explore the options.

After Tcl commands are entered they are sent to a Tcl interpreter. If the commands are recognized as valid Tcl commands, the command is executed and the result is sent to the tty. If a command is not a recognized Tcl command, it is sent to the Cisco IOS CLI parser. If the command is not a Tcl or Cisco IOS command, two error messages are displayed.

A predefined Tcl script can be created outside of Cisco IOS software, transferred to flash or disk memory, and run within Cisco IOS software. It is also possible to create a Tcl script and precompile the code before running it under Cisco IOS software. To exit from this mode, use the exit or the tclquit command to disable the use of the Tcl shell and return to privileged EXEC mode.

You can also use the tclsafe command with a script name such as tclsafe disk0:hello.tcl. The script hello.tcl executes immediately and allows you to exit from the untrusted safe mode and return to privileged EXEC mode.

Examples

The following example shows how to enable the Tcl shell untrusted safe mode and run info commands:
Router# tclsafe
Router(safe)(tcl)# info commands
info commands
tell socket subst open eof glob list pid time eval lrange tcl_trace fblocked lsearch gets 
case lappend proc break variable llength return linsert error catch clock info split array 
if fconfigure concat join lreplace source fcopy global switch update close cd for file 
append format read package set binary namespace scan seek while flush after vwait uplevel 
continue hostname foreach rename fileevent regexp upvar unset encoding expr load regsub 
interp history puts incr lindex lsort string
The following example shows how to execute the script hello.tcl to exit from the untrusted safe mode and return to privileged EXEC mode.
Router# tclsafe disk0:hello.tcl
Related Commands

Command

Description

scripting tcl trustpoint untrusted

Allows the interactive Tcl scripts to run regardless of the scripts failing the signature check.

tclquit

Quits Tcl shell.

tclsh

Enables the interactive Tcl shell and enters Tcl configuration mode.

Feature Information for Signed Tcl Scripts

Table 1 lists the release history for this feature.

Not all commands may be available in your Cisco IOS software release. For release information about a specific command, see the command reference document.

Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which Cisco IOS and Catalyst OS software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.t

Note Table 1 lists only the Cisco IOS software release that introduced support for a given feature in a given Cisco IOS software release train. Unless noted otherwise, subsequent releases of that Cisco IOS software release train also support that feature.

Table 1 Feature Information for Signed Tcl Scripts

Feature Name

Releases

Feature Information

Signed Tcl Scripts

12.4(15)T

The Signed Tcl Scripts feature allows you to create a certificate to generate a digital signature and sign a Tcl script with that digital signature.

The following commands were introduced by this feature: scripting tcl secure-mode, scripting tcl trustpoint name, scripting tcl trustpoint untrusted, and tclsafe.

Glossary

CA—certification authority. Service responsible for managing certificate requests and issuing certificates to participating IPsec network devices. This service provides centralized key management for the participating devices and is explicitly trusted by the receiver to validate identities and to create digital certificates.

certificates—Electronic documents that bind a user's or device's name to its public key. Certificates are commonly used to validate a digital signature.

CRL—certificate revocation list. Electronic document that contains a list of revoked certificates. The CRL is created and digitally signed by the CA that originally issued the certificates. The CRL contains dates for when the certificate was issued and when it expires. A new CRL is issued when the current CRL expires.

IPsec—IP security

peer certificate—Certificate presented by a peer, which contains the peer's public key and is signed by the trustpoint CA.

PKI—public key infrastructure. System that manages encryption keys and identity information for components of a network that participate in secured communications.

RA—registration authority. Server that acts as a proxy for the CA so that CA functions can continue when the CA is offline. Although the RA is often part of the CA server, the RA could also be an additional application, requiring an additional device to run it.

RSA keys—Public key cryptographic system developed by Ron Rivest, Adi Shamir, and Leonard Adleman. An RSA key pair (a public and a private key) is required before you can obtain a certificate for your router.

SHA1—Secure Hash Algorithm 1

SSH—secure shell

SSL—secure socket layer

Any Internet Protocol (IP) addresses used in this document are not intended to be actual addresses. Any examples, command display output, and figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses in illustrative content is unintentional and coincidental.

© 2007 Cisco Systems, Inc. All rights reserved.

Cisco IOS Software Releases 12.4 T

Signed Tcl Scripts

Hierarchical Navigation

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Table Of Contents

Signed Tcl Scripts

Contents

Prerequisites for Signed Tcl Scripts

Restrictions for Signed Tcl Scripts

Information About Signed Tcl Scripts

Cisco IOS PKI

RSA Key Pair

Certificate and Trustpoint

How to Configure Signed Tcl Scripts

Generating a Key Pair

SUMMARY STEPS

DETAILED STEPS

Generating a Certificate

SUMMARY STEPS

DETAILED STEPS

Signing the Tcl Scripts

SUMMARY STEPS

DETAILED STEPS

Verifying the Signature

SUMMARY STEPS

DETAILED STEPS

Converting the Signature into Nonbinary Data

SUMMARY STEPS

DETAILED STEPS

Configuring the Router with a Certificate

Prerequisites

SUMMARY STEPS

Verifying the Trustpoint

SUMMARY STEPS

DETAILED STEPS

Verifying the Signed Tcl Script

SUMMARY STEPS

DETAILED STEPS

What to Do Next

Configuration Examples for Signed Tcl Script

Generating a Key Pair: Example

Generating a Certificate: Example

Signing the Tcl Scripts: Example

Verifying the Signature: Example

Converting the Signature with Nonbinary Data: Example

Configuring the Router with a Certificate: Example

Additional References

Related Documents

Standards

MIBs

RFCs

Technical Assistance

Command Reference

scripting tcl secure-mode

Syntax Description

Command Default

Command Modes

Command History

Usage Guidelines

Examples

Related Commands

scripting tcl trustpoint name

Syntax Description

Command Default

Command Modes

Command History

Usage Guidelines

Examples

Related Commands

scripting tcl trustpoint untrusted

Syntax Description

Command Default

Command Modes

Command History

Usage Guidelines

Examples

Related Commands

tclsafe

Syntax Description

Command Default