Tcl Cryptography Documentation

NAME
tls - binding to OpenSSL toolkit.
DESCRIPTION
SYNOPSIS
package require Tcl ?8.5-?
package require tls
 
tls::cipher name
tls::ciphers ?protocol? ?verbose? ?supported?
tls::digests ?name?
tls::kdfs
tls::macs
tls::protocols
tls::version
 
tls::cmac -cipher name -key key ?options?
tls::digest -digest name ?options?
tls::hash -digest name ?options?
tls::hmac -digest name -key key ?options?
tls::md -digest name ?options?
tls::md4 data
tls::md5 data
tls::sha1 data
tls::sha256 data
tls::sha512 data
tls::unstack channelId
 
tls::encrypt -cipher name -key key ?options?
tls::decrypt -cipher name -key key ?options?
 
tls::hkdf -digest digest -key key ?options?
tls::pbkdf2 -size length -digest digest ?options?
tls::scrypt -password string -salt string ?options?
 
tls::random ?-private? length
 
tls::provider name
OPTIONS
COMMANDS
GLOSSARY
EXAMPLES
SPECIAL CONSIDERATIONS

NAME

tls - binding to OpenSSL toolkit.

DESCRIPTION

This extension provides a generic interface to the OpenSSL cryptography functions. The provided commands can be used to ensure the confidentiality, authenticity, and integrity of messages and data.


SYNOPSIS

package require Tcl 8.5-
package require tls

tls::cipher name
tls::ciphers ?protocol? ?verbose? ?supported?
tls::digests ?name?
tls::kdfs
tls::macs
tls::protocols
tls::version

tls::cmac -cipher name -key key ?options?
tls::digest -digest name ?options?
tls::hash -digest name ?options?
tls::hmac -digest name -key key ?options?
tls::md -digest name ?options?
tls::md4 data
tls::md5 data
tls::sha1 data
tls::sha256 data
tls::sha512 data
tls::unstack channelId

tls::encrypt -cipher name -key key ?options?
tls::decrypt -cipher name -key key ?options?

tls::hkdf -digest digest -key key ?options?
tls::pbkdf2 -size length -digest digest ?options?
tls::scrypt -password string -salt string ?options?

tls::random ?-private? length

tls::provider name


OPTIONS

The following options are used by the cryptography commands.


Cryptographic Options

-aad_data string
Additional Authenticated Data (AAD).
-cipher name
Name of symmetric cipher to use. Used by encrypt/decrypt command and CMAC & GMAC hash algorithms. For CMAC, it must be one of AES-128-CBC, AES-192-CBC, AES-256-CBC, or DES-EDE3-CBC. For GMAC it should be a GCM mode cipher (e.g. AES-128-GCM). See tls::ciphers command for the valid values. Only CCM and GCM modes (also known as Authenticated Encryption with Associated Data (AEAD) modes) provide both confidentially and integrity protection.
-digest name
-hash name
Name of hash function (aka message digest) to use. See tls::digests command for the valid values.
-info string
Optional context and application specific information. Can be a binary or text string. Max length is 1024 bytes for OpenSSL 1.1 and 2048 bytes for 3.0.
-iterations count
Number (integer > 0) of iterations to use in deriving the encryption key. Default is 2048. Some KDF implementations require an iteration count.
-iv string
Initialization vector (IV) to use. Required for some ciphers and GMAC. Other MACs use a fixed IV. Cipher modes CBC, CFB, and OFB all need an IV, while ECB and CTR modes do not. A new, random IV should (must for OFB) be created for each use. Think of the IV as a nonce (number used once), it's public but random and unpredictable. See the tls::cipher for iv_length and when required (length > 0). Max is 16 bytes. If not set, it will default to \x00 fill data.
-key string
Encryption key to use for cryptography function. Can be a binary or text string. Longer keys provide better protection. Used by ciphers, HMAC, some CMAC, and some KDF implementations. If the length of the key is < key_length it will be padded. Max is 64 bytes. If > key_length, it will be rejected. See the tls::cipher for key_length.
-mac name
Name of Message Authentication Code (MAC) to use. See tls::macs command for the valid values.
-padding boolean
Specifies whether to use PKCS#7 padding or not for block ciphers. If true, 1 to block size number of pad bytes will be added to the output to pad to the next block size. Default is true.
-password string
Password to use for some KDF functions. If not specified, the default value is used. Can be a binary or text string. For KDF commands, this is the same as the -key option.
-properties list
List of additional properties to pass to cryptographic function.
-salt string
Specifies salt value to use when encrypting data. Can be a binary or text string. Default is to use a string of \0's. It is best to use a uniquely and randomly generated value. This option is used by BLAKE2 MAC and some KDF implementations use a non-secret unique cryptographic salt.
-length integer
-size integer
Set the output length in bytes. Used by KDFs, KMAC128 and KMAC256 MACs, and SHAKE128 and SHAKE256 XOF hashes. The default length for KMAC128 is 32 bytes and KMAC256 is 64 bytes. The default length for SHAKE128 is 16 bytes and SHAKE256 is 32 bytes.
-tag string
-tag string
Authenticated Encryption and Authenticated Data (AEAD) tag. Can be a binary or text string. Max is 16 bytes. A minimum of 12 bytes is recommended.
-xof boolean
Set whether to use XOF. This option is used by KMAC.

Input/Output Options

-chan channelId
-channel channelId
Add the cryptographic transformation on top of channel channelId. Automatically sets channel to binary mode. Works like chan push to create a stacked channel. If the command fileevent is to be used for channel event monitoring, all channels in the stack should be set to non-blocking mode. If not, the system may hang while waiting for data. When done, use either the close command or tls::unstack to remove the transform from the channel. Additional transforms cannot be added to channel. Example code:
set ch [open test_file.txt rb]
::tls::digest -digest sha256 -chan $ch
set data ""
while {![eof $ch]} {append data [read $ch 4096]}
close $ch
puts $data
-command cmdName
Create and return cmdName which is used to incrementally add data to a cryptographic function. To add data to the function, call "cmdName update data", where data is the data to add. When done, call "cmdName finalize" to return the resulting value and delete cmdName. Example code:
set cmd [::tls::digest -digest sha256 -command ::tls::temp]
set data ""
append data [$cmd update "Some data. "]
append data [$cmd update "More data."]
append data [$cmd finalize]
puts $data
-data string
Perform the cryptographic function on data and return the result. Example code:
set md [::tls::digest sha256 "Some example data."]
puts $md
-file filename
-filename filename
Perform the cryptographic function on file filename and return the result. This operation will open file, read the file data, close the file, and return the result using the TCL file APIs, so VFS files are supported. Example code:
set md [::tls::digest -digest sha256 -file test_file.txt]
puts $md
-infile filename
Specifies the file to use as data input source. This option uses the TCL file APIs, so VFS files are supported. Example code:
::tls::encrypt -cipher aes-128-cbc -key "Test key" -infile unencrypted.txt -outfile encrypted.dat
-outfile filename
Specifies the file to output the encryption results to. This option uses the TCL file APIs, so VFS files are supported. Example code:
::tls::decrypt -cipher aes-128-cbc -key "Test key" -infile encrypted.dat -outfile unencrypted.txt
-keyfile filename
Specifies the file to get the encryption key from.

Format Options

-base64
Base64 encode data after encryption or decode before decryption.
-bin
-binary
Output result of function as a binary string.
-hex
-hexadecimal
Output result of function as a hexadecimal string. This is the default option unless otherwise specified.

COMMANDS

The following commands provide access to the OpenSSL cryptography functions.

Info Commands

These commands provide information about the available ciphers, digests, etc. and their properties.

tls::cipher name
Returns a list of property name and value pairs describing cipher name. Properties are:
nidInternal id of cipher. This is the same as name.
nameName or alias of the cipher.
descriptionDescription of the cipher. OpenSSL 3.0+ only.
block_sizeBlock size of the cipher. Stream ciphers are set to 1.
key_lengthkey length of a cipher in bytes.
iv_lengthIV length of a cipher in bytes or 0 if not used.
typeBase type of this cipher or undefined if none.
providerProvider of the cipher. OpenSSL 3.0+ only.
modeBlock cipher mode or stream for a stream cipher.
flagsFlags associated with the cipher. Includes: Variable Length, AEAD Cipher, Non FIPS Allow, etc.
tls::ciphers ?protocol? ?verbose? ?supported?
Without any args, returns a list of all symmetric ciphers for use with the -cipher option. With protocol, only the ciphers supported for that protocol are returned. See tls::protocols command for the supported protocols. If verbose is specified as true then a verbose, human readable list is returned with additional information on the cipher. If supported is specified as true, then only the ciphers supported for protocol will be listed.
tls::digests ?name?
Without name, returns a list of the supported message digests (aka hash algorithms) for use with the -digest option. With name, returns a list of property name and value pairs describing message digest name. Properties are:
nameName or alias of the digest.
descriptionDescription of the digest. OpenSSL 3.0+ only.
sizeSize of the digest in bits.
block_sizeBlock size of digest in bytes.
providerProvider of the digest. OpenSSL 3.0+ only.
typeBase type of this digest or undefined if none.
pkey_typePkey associated with digest.
flagsFlags associated with the digest. Includes: One-shot (only one update (no incremental) allowed), XOF (variable length), etc.
tls::kdfs
Returns a list of the available Key Derivation Function (KDF) algorithms. Each item in the list corresponds to a command with the same name.
tls::macs
Returns a list of the available Message Authentication Codes (MAC). Each item in the list corresponds to a command with the same name.
tls::protocols
Returns a list of supported protocols. Valid values are: ssl2, ssl3, tls1, tls1.1, tls1.2, and tls1.3. Exact list depends on OpenSSL version and compile time flags.
tls::version
Returns the OpenSSL version string.

Message Digest (MD) and Message Authentication Code (MAC) Commands

These commands calculate a message digest or message authentication code for data.

tls::cmac ?-cipher? name -key key ? -bin|-hex ?[-chan channelId | -command cmdName | -file filename | ?-data? data]
Calculate the Cipher-based Message Authentication Code (CMAC) where key is a shared key and output the result per the I/O options in the specified format. MACs are used to ensure authenticity and the integrity of data. See options for usage info. Option -key is only used for some ciphers.
tls::digest option value ...
Alias for tls::md.
tls::hash option value ...
Alias for tls::md.
tls::hmac ?-digest? name -key key ? -bin|-hex ?[-chan channelId | -command cmdName | -file filename | ?-data? data]
Calculate the Hash-based Message Authentication Code (HMAC) where key is a shared secret key and output the result per the I/O options in the specified format. The cryptographic strength depends upon the size of the key and the security of the hash function used. See options for usage info.
tls::mac ?-mac? name -cipher name -digest name -key key ?-bin|-hex? ?-length|-size length? [-chan channelId | -command cmdName | -file filename | ?-data? data]
(OpenSSL 3.0+) Calculate the Message Authentication Code (MAC) where key is a shared key and output the result per the I/O options in the specified format. MACs are used to ensure authenticity and the integrity of data. See options for usage info.
tls::md ?-digest? name ?-bin|-hex? ?-length|-size length? [-chan channelId | -command cmdName | -file filename | ?-data? data]
Calculate the message digest (MD) using hash function name and output the result per the I/O options in the specified format. MDs are used to ensure the integrity of data. See options for usage info.
tls::md4 data
Returns the MD4 message-digest for data as a hex string.
tls::md5 data
Returns the MD5 message-digest for data as a hex string.
tls::sha1 data
Returns the SHA1 secure hash algorithm digest for data as a hex string.
tls::sha256 data
Returns the SHA-2 SHA256 secure hash algorithm digest for data as a hex string.
tls::sha512 data
Returns the SHA-2 SHA512 secure hash algorithm digest for data as a hex string.
tls::unstack channelId
Removes the top level cryptographic transform from channel channelId.

Encryption and Decryption Commands

These commands encrypt plaintext into ciphertext or vice versa.

tls::encrypt ?-cipher? name -digest name -key key ? -iv string? [-chan channelId | -command cmdName | -infile filename -outfile filename | -data data]
Encrypt the data using cipher cipher and output the result per the I/O options. Ciphers are used to create the cipher text from the input data. See options for usage info. Option -iv is only used for some ciphers. See the tls::cipher command for key and iv sizes and for when the -iv option is used (iv_length > 0).
tls::decrypt ?-cipher? name -key key ? -iv string? [-chan channelId | -command cmdName | -infile filename -outfile filename | -data data]
Decrypt the data using cipher cipher and output the result per the I/O options. This command is the opposite of the tls::encrypt command. See options for usage info. The -iv option is only used for some ciphers. See the tls::cipher command for key and iv sizes and for when the -iv option is used (iv_length > 0).

Key Derivation Function (KDF) Commands

These commands are a more secure way to generate keys and ivs for use by the tls::encrypt command then regular strings and random values.

tls::hkdf -digest digest -key string ?-info string? ?-salt string? ?-length|-size length?
Derive a key of size length using the HMAC-based Extract-and-Expand Key Derivation Function (HKDF). See options for usage info.
tls::pbkdf2 [-cipher cipher | -length length] -digest digest ?-iterations count? ?-password string? ?-salt string?
Derive a key and initialization vector (iv) from a password and salt value using PKCS5_PBKDF2_HMAC. See options for usage info. If -cipher is specified, then the derived key and iv sized for that cipher are returned as a key-value list. If not or if -size is specified, then the derived key (DK) of length bytes is returned.
tls::scrypt -password string -salt string ?-N costParameter? ?-r blockSize? ?-p parallelization? ?-length|-size length?
Derive a key of size length using the scrypt password based key derivation function. See options for usage info. See RFC 7914 for more details. Can consume a large amount of memory. RAM used is roughly (128 * N * r * p) bytes. Memory is limited to 1025 MiB. The custom options are:
-NThe CPU/Memory cost parameter must be larger than 1, a power of 2, and less than 2^(128 * r / 8). Default is 1048576.
-rThe blockSize parameter specifies the block size. Must be greater than 0. Default is 8.
-pThe parallelization parameter must be a positive integer less than or equal to ((2^32-1) * 32) / (128 * r). Default is 1.

Random Bytes Commands

These commands provide randomly generated byte strings for use when random data is needed.

tls::random ?-private? length
Generate length random bytes using a cryptographically secure pseudo random generator (CSPRNG). OpenSSL uses a security level of 256 bits. Will return an error if a trusted entropy source such as the OS isn't available. Use -private option if the values are intended to remain private in case the public PRNG is compromised.

Load Provider

These commands provide access to the OpenSSL providers.

tls::provider name
Load name default provider. Valid provider names are: default, base, fips, and legacy. Use legacy to load the legacy provider ciphers, digests, etc.

GLOSSARY

The following is a list of the terminology used in this package along with brief definitions. For more details, please consult with the OpenSSL documentation.

AADAdditional Authenticated Data
AEADAuthenticated Encryption with Associated Data
AESAdvanced Encryption Standard
CBCAES Cipher Block Chaining mode
CFBAES Cipher Feedback mode
CTRAES Counter mode
ECBAES Electronic Codebook mode
IVInitialization vector
KDFKey Derivation Function
MACMessage Authenticated Code
MDMessage Digest
OFBAES Output Feedback mode
SHASecure Hash Algorithm
SSLSecure Sockets Layer
TLSTransport Layer Security
XOFExtendable-Output Function (aka variable length)

EXAMPLES

TBS


TBD

SPECIAL CONSIDERATIONS

The capabilities of this package can vary enormously based upon how your OpenSSL library was configured and built. New versions may obsolete older ciphers, digests, MACs, etc. or change default values. Use the info commands to obtain the supported values.


Copyright © 2023 Brian O'Hagan.