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# pki(n) 0.10 tcllib "public key encryption"

## Name

pki - Implementation of the public key cipher

## Synopsis

- package require Tcl 8.5
- package require pki ?0.10?

- ::pki::encrypt ?-binary? ?-hex? ?-pad? ?-nopad? ?-priv? ?-pub? ?--? input key
- ::pki::decrypt ?-binary? ?-hex? ?-unpad? ?-nounpad? ?-priv? ?-pub? ?--? input key
- ::pki::sign input key ?algo?
- ::pki::verify signedmessage plaintext key ?algo?
- ::pki::key key ?password? ?encodePem?
- ::pki::pkcs::parse_key key ?password?
- ::pki::x509::parse_cert cert
- ::pki::rsa::generate bitlength ?exponent?
- ::pki::x509::verify_cert cert trustedcerts ?intermediatecerts?
- ::pki::x509::validate_cert cert ?-sign_message dn_of_signer? ?-encrypt_message dn_of_signer? ?-sign_cert dn_to_be_signed ca_depth? ?-ssl dn?
- ::pki::pkcs::create_csr keylist namelist ?encodePem? ?algo?
- ::pki::pkcs::parse_csr csr
- ::pki::x509::create_cert signreqlist cakeylist serial_number notBefore notAfter isCA extensions ?encodePem? ?algo?

## Description

## COMMANDS

::pki::encrypt ?-binary? ?-hex? ?-pad? ?-nopad? ?-priv? ?-pub? ?--? input key

  Encrypt a message using PKI (probably RSA).

  Requires the caller to specify either -priv to encrypt with the private key or -pub to encrypt with the public key. The default option is to pad and return in hex. One of -pub or -priv must be specified.

  The -hex option causes the data to be returned in encoded as a hexidecimal string, while the -binary option causes the data to be returned as a binary string. If they are specified multiple times, the last one specified is used.

  The -pad option causes the data to be padded per PKCS#1 prior to being encrypted. The -nopad inhibits this behaviour. If they are specified multiple times, the last one specified is used.

  The input to encrypt is specified as input.

  The key parameter, holding the key to use, is a return value from either ::pki::pkcs::parse_key, ::pki::x509::parse_cert, or ::pki::rsa::generate.

  Mapping to OpenSSL's openssl application:

  1. "openssl rsautl -encrypt" == "::pki::encrypt -binary -pub"

  2. "openssl rsautl -sign" == "::pki::encrypt -binary -priv"

::pki::decrypt ?-binary? ?-hex? ?-unpad? ?-nounpad? ?-priv? ?-pub? ?--? input key

  Decrypt a message using PKI (probably RSA). See ::pki::encrypt for option handling.

  Mapping to OpenSSL's openssl application:

  1. "openssl rsautl -decrypt" == "::pki::decrypt -binary -priv"

  2. "openssl rsautl -verify" == "::pki::decrypt -binary -pub"

::pki::sign input key ?algo?

  Digitally sign message input using the private key.

  If algo is ommited "sha1" is assumed. Possible values for algo include "md5", "sha1", "sha256", and "raw". Specifying "raw" for algo will inhibit the building of an ASN.1 structure to encode which hashing algorithm was chosen. Attention: In this case the corresponding pkgi::verify must be called with algorithm information. Conversely, specifying a non-"raw" algorithm here means that the corresponding pkgi::verify invokation has to be made without algorithm information.

  The input should be the plain text, hashing will be performed on it.

  The key should include the private key.

::pki::verify signedmessage plaintext key ?algo?

  Verify a digital signature using a public key. Returns true or false.

  Attention: The algorithm information algo has to be specified if and only if the pki::sign which generated the signedmessage was called with algorithm "raw". This inhibited the building of the ASN.1 structure encoding the chosen hashing algorithm. Conversely, if a proper algorithm was specified during signing then you must not specify an algorithm here.

::pki::key key ?password? ?encodePem?

  Convert a key structure into a serialized PEM (default) or DER encoded private key suitable for other applications. For RSA keys this means PKCS#1.

::pki::pkcs::parse_key key ?password?

  Convert a PKCS#1 private key into a usable key, i.e. one which can be used as argument for ::pki::encrypt, ::pki::decrypt, ::pki::sign, and ::pki::verify.

::pki::x509::parse_cert cert

  Convert an X.509 certificate to a usable (public) key. The returned dictionary can be used as argument for ::pki:encrypt, ::pki::decrypt, and ::pki::verify. The cert argument can be either PEM or DER encoded. In addition to the public keying information, the dictionary contains the following keys containing certificate content as defined in RFC5280:

  - subject holds the name of the subject from the certificate.

  - issuer holds the name of the issuing CA.

  - serial_number holds the serial number of the certificate.

  - notBefore holds the starting date for certificate validity.

  - notAfter holds the ending date for certificate validity.

  - version holds the X.509 version format.

  - extensions holds a dictionary containing the extensions included in the certificate (see below).

  The dictionary holds additional entries related to keying. These are intended for use of the above-mentioned commands for cryptographic operations.

  The extensions key in the returned dictionary holds a nested dictionary whose keys correspond to the names (with same exact case) in Certificate Extensions in RFC5280. The format of each value is also based on the ASN.1 structures defined there. See the Examples for an illustration.

::pki::rsa::generate bitlength ?exponent?

  Generate a new RSA key pair, the parts of which can be used as argument for ::pki::encrypt, ::pki::decrypt, ::pki::sign, and ::pki::verify.

  The bitlength argument is the length of the public key modulus.

  The exponent argument should generally not be specified unless you really know what you are doing.

::pki::x509::verify_cert cert trustedcerts ?intermediatecerts?

  Verify that a trust can be found between the certificate specified in the cert argument and one of the certificates specified in the list of certificates in the trustedcerts argument. (Eventually the chain can be through untrusted certificates listed in the intermediatecerts argument, but this is currently unimplemented). The certificates specified in the cert and trustedcerts option should be parsed (from ::pki::x509::parse_cert).

::pki::x509::validate_cert cert ?-sign_message dn_of_signer? ?-encrypt_message dn_of_signer? ?-sign_cert dn_to_be_signed ca_depth? ?-ssl dn?

  Validate that a certificate is valid to be used in some capacity. If multiple options are specified they must all be met for this procedure to return "true".

  Currently, only the -sign_cert option is functional. Its arguments are dn_to_be_signed and ca_depth. The dn_to_be_signed is the distinguished from the subject of a certificate to verify that the certificate specified in the cert argument can sign. The ca_depth argument is used to indicate at which depth the verification should be done at. Some certificates are limited to how far down the chain they can be used to verify a given certificate.

::pki::pkcs::create_csr keylist namelist ?encodePem? ?algo?

  Generate a certificate signing request from a key pair specified in the keylist argument.

  The namelist argument is a list of "name" followed by "value" pairs to encoding as the requested distinguished name in the CSR.

  The encodePem option specifies whether or not the result should be PEM encoded or DER encoded. A "true" value results in the result being PEM encoded, while any other value 9results in the the result being DER encoded. DER encoding is the default.

  The algo argument specifies the hashing algorithm we should use to sign this certificate signing request with. The default is "sha1". Other possible values include "md5" and "sha256".

::pki::pkcs::parse_csr csr

  Parse a Certificate Signing Request. The csr argument can be either PEM or DER encoded. The command returns a dictionary that includes the following keys:

  - subject - contains the subject name from the CSR.

  - type - contains the public key algorithm name. Currently only rsa is supported.

  - extensionRequest - contains a dictionary with the contents of the extensionRequest information in the CSR. This has the same form as described for the extensions dictionary in the documentation for parse_cert.

  There may be other keys in the dictionary related to the public key algorithm in use.

::pki::x509::create_cert signreqlist cakeylist serial_number notBefore notAfter isCA extensions ?encodePem? ?algo?

  Sign a signing request (usually from ::pki::pkcs::create_csr or ::pki::pkcs::parse_csr) with a Certificate Authority (CA) certificate.

  The signreqlist argument should be the parsed signing request.

  The cakeylist argument should be the parsed CA certificate.

  The serial_number argument should be a serial number unique to this certificate from this certificate authority.

  The notBefore and notAfter arguments should contain the time before and after which (respectively) the certificate should be considered invalid. The time should be encoded as something clock format will accept (i.e., the results of clock seconds and clock add).

  The isCA argument is a boolean argument describing whether or not the signed certificate should be a a CA certificate. If specified as true the "id-ce-basicConstraints" extension is added with the arguments of "critical" being true, "allowCA" being true, and caDepth being -1 (infinite).

  The extensions argument is a list of extensions and their parameters that should be encoded into the created certificate. Currently only one extension is understood ("id-ce-basicConstraints"). It accepts three arguments critical allowCA caDepth. The critical argument to this extension (and any extension) whether or not the validator should reject the certificate as invalid if it does not understand the extension (if set to "true") or should ignore the extension (if set to "false"). The allowCA argument is used to specify as a boolean value whether or not we can be used a certificate authority (CA). The caDepth argument indicates how many children CAs can be children of this CA in a depth-wise fashion. A value of "0" for the caDepth argument means that this CA cannot sign a CA certificate and have the result be valid. A value of "-1" indicates infinite depth.

## EXAMPLES

The example below retrieves a certificate from www.example.com using the TLS extension and dumps its content.

        % set so [tls::socket www.example.com 443]
        sock00000229EB84E710
        % tls::handshake $so
        1
        % set status [tls::status $so]
        ...output not shown...
        % set cert_pem [dict get $status certificate]
        ...output not shown...
        % set cert [::pki::x509::parse_cert $cert_pem]
        ...output not shown...
        % dict get $cert subject
        C=US, ST=California, L=Los Angeles, O=Internet Corporation for Assigned Names and Numbers, CN=www.example.org
        % dict get $cert issuer
        C=US, O=DigiCert Inc, CN=DigiCert TLS RSA SHA256 2020 CA1
        % clock format [dict get $cert notAfter]
        Sun Dec 26 05:29:59 +0530 2021
        % set extensions [dict get $cert extensions]
        ...output not shown...
        % dict keys $extensions
        authorityKeyIdentifier subjectKeyIdentifier subjectAltName keyUsage extKeyUsage cRLDistributionPoints certificatePolicies authorityInfoAccess id-ce-basicConstraints basicConstraints 1.3.6.1.4.1.11129.2.4.2
        dict get $extensions basicConstraints
        1 {0 -1}
        % dict get $extensions keyUsage
        1 {5 digitalSignature keyEncipherment}
        % dict get $extensions extKeyUsage
        0 {serverAuth clientAuth}
        % dict get $extensions subjectAltName
        0 {dNSName www.example.org dNSName example.com dNSName example.edu dNSName example.net dNSName example.org dNSName www.example.com dNSName www.example.edu dNSName www.example.net}
        % dict get $extensions basicConstraints
        1 {0 -1}
        % dict get $extensions keyUsage
        1 {5 digitalSignature keyEncipherment}
        % dict get $extensions extKeyUsage
        0 {serverAuth clientAuth}

## REFERENCES

1. Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile

2. New ASN.1 Modules for the Public Key Infrastructure Using X.509 (PKIX)

3. PKCS #10: Certification Request Syntax Specification

## AUTHORS

Roy Keene, Ashok P. Nadkarni

## Bugs, Ideas, Feedback

This document, and the package it describes, will undoubtedly contain bugs and other problems. Please report such in the category rsa of the Tcllib Trackers. Please also report any ideas for enhancements you may have for either package and/or documentation.

When proposing code changes, please provide unified diffs, i.e the output of diff -u.

Note further that attachments are strongly preferred over inlined patches. Attachments can be made by going to the Edit form of the ticket immediately after its creation, and then using the left-most button in the secondary navigation bar.

## See Also

aes(n), blowfish(n), des(n), md5(n), sha1(n)

## Keywords

cipher, data integrity, encryption, public key cipher, rsa, security

## Category

Hashes, checksums, and encryption

## Copyright

Copyright © 2010, 2011, 2012, 2013, 2021 Roy Keene, Andreas Kupries, Ashok P. Nadkarni