TLS (SSL) TCL Commands

Name

+

tls - binding to the OpenSSL library for encrypted socket and I/O channel communications

+

Synopsis

+

package require Tcl 8.5-
package require tls 1.8

+

tls::init ?-option? ?value? ?-option value ...?
tls::socket ?-option? ?value? ?-option value ...? host port
tls::socket -server command ?-option? ?value? ?-option value ...? port
tls::import channel ?-option? ?value? ?-option value ...?
tls::unimport channel
tls::handshake channel
tls::status ?-local? channel
tls::connection channel
tls::ciphers ?protocol? ?verbose? ?supported?
tls::protocols
tls::version

+

This extension provides TCL script access to secure socket communications using the Transport Layer Security (TLS) protocol. It provides a generic binding to OpenSSL, utilizing the -Tcl_StackChannel API in TCL 8.4 and higher. -These sockets behave exactly the same as channels created using the built-in -socket command, along with additional options for controlling -the SSL/TLS session. -

-
- -

- -

COMMANDS

- -

Typically one would use the tls::socket command -which provides compatibility with the native TCL socket -command. In such cases tls::import should not be -used directly.

-

tls::init ?options?: Optional function to set the default options used by - tls::socket. If you call tls::import - directly, this command has no effect. This command supports all of the - same options as the tls::socket command, though you - should limit your options to only TLS related ones.

tls::socket ?options? - host port
tls::socket ?-server command? ?options? port: This is a helper function that utilizes the underlying commands - (socket and tls::import) to create - the connection. It behaves the same as the native TCL socket - command, but also supports the tls:import - command options and one additional option:
tls::import channel - ?options?: Add SSL/TLS encryption to a regular TCL channel. It need - not be a socket, but must provide bi-directional flow. Also - set session parameters for SSL handshake.
tls::unimport channel: Provided for symmetry to tls::import, this - unstacks the encryption of a regular TCL channel. An error - is thrown if TLS is not the top stacked channel type.

tls::handshake - channel: Forces handshake to take place, and returns 0 if - handshake is still in progress (non-blocking), or 1 if - the handshake was successful. If the handshake failed - this routine will throw an error.

tls::status - ?-local? channel: Returns the current status of an SSL channel. The result is a list - of key-value pairs describing the SSL, certificate, and certificate - verification status. If the SSL handshake has not yet completed, - an empty list is returned. If -local is specified, then the - local certificate is used.
tls::connection - channel: Returns the current connection status of an SSL channel. The - result is a list of key-value pairs describing the connection.
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::protocols: Returns a list of the supported SSL/TLS 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.

-
- -

- -

CERTIFICATE VALIDATION

- -

Summary of command line options:

-

The following options are used for certificate validation:

-

The -cadir option specifies the directory where the Certificate -Authority (CA) certificates are stored. The default is platform specific, but -is usually "/etc/ssl/certs" on Linux/Unix systems. The default location can be -overridden via the SSL_CERT_DIR environment variable.
The -cafile option specifies the file that contains all of the -Certificate Authority (CA) certificates in the PEM file format. The default is -cert.pem, in the OpenSSL directory. On Linux/Unix systems, this is -usually "/etc/ssl/ca-bundle.pem". The default file can be overridden via the -SSL_CERT_FILE environment variable.
The -castore option contains the URI to the Certificate Authority -(CA) store, which may be a single container or a catalog of containers. -Starting with OpenSSL 3.2 on Windows, set this to "org.openssl.winstore://" to -use the built-in Windows Certificate Store. The Windows cert store only -supports root certificate stores.
The -request option is used to request the server send its -certificate chain as part of the connection negotiation process. This is -needed to do certificate validation. The default is true. In addition, the -client can manually inspect and accept or reject each certificate using the --validatecommand option.
The -require option is used to require certificate validation be -performed as part of the connection negotiation process. A valid CA directory, -file, or store must be present for this to work.

- -
-

When are command line options needed:

-

-By default, a client TLS connection does NOT validate the server certificate +Tcl_StackChannel API in TCL 8.4 and higher. +These sockets behave exactly the same as channels created using the built-in +socket command, along with additional options for controlling +the SSL/TLS session.

+

Commands

+

Typically one would use the tls::socket command to create a new encrypted +TCP socket. It is compatible with the native TCL ::socket command. +Alternatively for an existing TCP socket, the tls::import command can be +used to start TLS on the connection.

+

tls::init ?-option? ?value? ?-option value ...?

Optional function to set the default options used by tls::socket. If you +call tls::import directly, this command has no effect. This command +supports all of the same options as the tls::socket command, though you +should limit your options to only TLS related ones.

tls::socket ?-option? ?value? ?-option value ...? host port

This is a helper function that utilizes the underlying commands socket +and tls::import to create the connection. It behaves the same as the +native TCL socket command, but also supports the tls:import +command options with one additional option. It returns the channel handle id +for the new socket.

+

-autoservername bool: If true, automatically set the -servername argument to the +host argument. Default is false.

tls::socket -server command ?-option? ?value? ?-option value ...? port

Same as previous, but instead creates a server socket for clients to connect to +just like the Tcl socket -server command. It returns the channel +handle id for the new socket.

tls::import channel ?-option? ?value? ?-option value ...?

Start TLS encryption on TCL channel channel via a stacked channel. It +need not be a socket, but must provide bi-directional flow. Also sets session +parameters for SSL handshake. Valid options are:

+

-alpn list: List of protocols to offer during Application-Layer Protocol Negotiation +(ALPN). For example: h2 and http/1.1, but not h3 or +quic.
-cadir directory: Specifies the directory where the Certificate Authority (CA) certificates are +stored. The default is platform specific and can be set at compile time. The +default location can be overridden by the SSL_CERT_DIR environment +variable. See Certificate Validation for more details.
-cafile filename: Specifies the file with the Certificate Authority (CA) certificates to use. +The default is "cert.pem", in the OpenSSL directory. The default file can +be overridden by the SSL_CERT_FILE environment variable. See +Certificate Validation for more details.
-castore URI: Specifies the Uniform Resource Identifier (URI) for the Certificate Authority +(CA) store, which may be a single container or a catalog of containers. +Starting with OpenSSL 3.2 on Windows, set to "org.openssl.winstore://" +to use the built-in Windows Certificate Store. This store only supports root +certificate stores. See Certificate Validation for more details.
-certfile filename: Specifies the name of the file with the certificate in PEM format to use +as the local (client or server) certificate. It also contains the public key.
-cert string: Specifies the certificate to use as a DER encoded string (X.509 DER).
-cipher string: Specifies the list of ciphers to use for TLS 1.2 and earlier connections. +String is a colon ":" separated list of ciphers. +Ciphers can be combined using the "+" character. +Prefixes can be used to permanently remove "!", delete "-", or +move to the end "+" a specified cipher. +Keywords @STRENGTH (sort by algorithm key length), +@SECLEVEL=n (set security level to n), and +DEFAULT (use default cipher list, at start only) can also be specified. +See the OpenSSL +documentation for the full list of valid values.
-ciphersuites string: Specifies the list of cipher suites to use for TLS 1.3 as a colon +":" separated list of cipher suite names. See the +OpenSSL +documentation for the full list of valid values.
-command callback: Specifies the callback command to be invoked at several points during the +handshake to pass errors, tracing information, and protocol messages. +See Callback Options for more info.
-dhparams filename: Specifies the Diffie-Hellman (DH) parameters file.
-keyfile filename: Specifies the private key file. The default value is to use the file +specified by the -certfile option.
-key string: Specifies the private key to use as a DER encoded string (PKCS#1 DER).
-model channel: Force this channel to share the same SSL_CTX structure as the +specified channel, and therefore share config, callbacks, etc.
-password callback: Specifies the callback command to invoke when OpenSSL needs to obtain a +password. This is typically used to unlock the private key of a certificate. +The callback should return a password string. See Callback Options +for more info.
-post_handshake bool: Allow post-handshake session ticket updates.
-request bool: Request a certificate from peer during the SSL handshake. This is needed to do +Certificate Validation. Default is true. +See Certificate Validation for more details.
-require bool: Require a valid certificate from peer during the SSL handshake. If this is set to +true, then -request must also be set to true and a either -cadir, +-cafile, -castore, or a platform default must be provided in order to +validate against. The default is false since not all platforms have +certificates to validate against in a form compatible with OpenSSL. +See Certificate Validation for more details.
-security_level integer: Specifies the security level (value from 0 to 5). The security level affects +the allowed cipher suite encryption algorithms, supported ECC curves, +supported signature algorithms, DH parameter sizes, certificate key sizes +and signature algorithms. The default is 1 prior to OpenSSL 3.2 and 2 +thereafter. Level 3 and higher disable support for session tickets and +only accept cipher suites that provide forward secrecy.
-server bool: Specifies whether to act as a server and respond with a server handshake when a +client connects and provides a client handshake. The default is false.
-servername hostname: Specify the peer's hostname. This is used to set the TLS Server Name +Indication (SNI) extension. Set this to the expected servername in the +server's certificate or one of the Subject Alternate Names (SAN).
-session_id binary_string: Specifies the session id to resume a session. Not supported yet.
-ssl2 bool: Enable use of SSL v2. The default is false. Note: Recent versions of +OpenSSL no longer support SSLv2, so this may not have any effect. See the +tls::protocols command for supported protocols.
-ssl3 bool: Enable use of SSL v3. The default is false. Note: Recent versions +of OpenSSL may have this disabled at compile time, so this may not have any +effect. See the tls::protocols command for supported protocols.
-tls1 bool: Enable use of TLS v1. The default is true. Note: TLS 1.0 needs +SHA1 to operate, which is only available in security level 0 for Open SSL 3.0+. +See the -security_level option.
-tls1.1 bool: Enable use of TLS v1.1. The default is true. Note: TLS 1.1 needs +SHA1 to operate, which is only available in security level 0 for Open SSL 3.0+. +See the -security_level option.
-tls1.2 bool: Enable use of TLS v1.2. The default is true.
-tls1.3 bool: Enable use of TLS v1.3. The default is true.
-validatecommand callback: Specifies the callback command to invoke to validate the peer certificates +and other config info during the protocol negotiation phase. This can be used +by TCL scripts to perform their own Certificate Validation to supplement the +default validation provided by OpenSSL. The script must return a boolean true +to continue the negotiation. See Callback Options for more info.

tls::unimport channel

Compliment to tls::import. Used to remove the top level stacked channel +from channel. This unstacks the encryption of a regular TCL channel. An +error is thrown if TLS is not the top stacked channel type.

tls::handshake channel

Forces the TLS negotiation handshake to take place immediately, and returns 0 +if handshake is still in progress (non-blocking), or 1 if the handshake was +successful. If the handshake failed, an error will be returned.

tls::status ?-local? channel

Returns the current status of an SSL channel. The result is a list of key-value +pairs describing the SSL, certificate, and certificate verification status. If +the SSL handshake has not yet completed, an empty list is returned. If the +-local option is specified, then the local certificate is used. Returned +values include:

+

SSL Status

+

alpn protocol: The protocol selected after Application-Layer Protocol Negotiation (ALPN).
cipher cipher: The current cipher in use for the session.
peername name: The peername from the certificate.
protocol version: The protocol version used for the connection: SSL2, SSL3, TLS1, TLS1.1, TLS1.2, TLS1.3, or unknown.
sbits n: The number of bits used for the session key.
signatureHashAlgorithm algorithm: The signature hash algorithm.
signatureType type: The signature type value.
verifyDepth n: Maximum depth for the certificate chain verification. Default is -1, to check all.
verifyMode list: List of certificate verification modes.
verifyResult result: Certificate verification result.
ca_names list: List of the Certificate Authorities used to create the certificate.

+

Certificate Status

+

all string: Dump of all certificate info.
version value: The certificate version.
serialNumber string: The serial number of the certificate as a hex string.
signature algorithm: Cipher algorithm used for certificate signature.
issuer string: The distinguished name (DN) of the certificate issuer.
notBefore date: The beginning date of the certificate validity.
notAfter date: The expiration date of the certificate validity.
subject string: The distinguished name (DN) of the certificate subject. Fields include: Common +Name (CN), Organization (O), Locality or City (L), State or Province (S), and +Country Name (C).
issuerUniqueID string: The issuer unique id.
subjectUniqueID string: The subject unique id.
num_extensions n: Number of certificate extensions.
extensions list: List of certificate extension names.
authorityKeyIdentifier string: Authority Key Identifier (AKI) of the Issuing CA certificate that signed the +SSL certificate as a hex string. This value matches the SKI value of the +Intermediate CA certificate.
subjectKeyIdentifier string: Subject Key Identifier (SKI) hash of the public key inside the certificate as a +hex string. Used to identify certificates that contain a particular public key.
subjectAltName list: List of all of the Subject Alternative Names (SAN) including domain names, sub +domains, and IP addresses that are secured by the certificate.
ocsp list: List of all Online Certificate Status Protocol (OCSP) URLs that can be used to +check the validity of this certificate.
certificate cert: The PEM encoded certificate.
signatureAlgorithm algorithm: Cipher algorithm used for the certificate signature.
signatureValue string: Certificate signature as a hex string.
signatureDigest version: Certificate signing digest as a hex string.
publicKeyAlgorithm algorithm: Certificate signature public key algorithm.
publicKey string: Certificate signature public key as a hex string.
bits n: Number of bits used for certificate signature key.
self_signed boolean: Whether the certificate signature is self signed.
sha1_hash hash: The SHA1 hash of the certificate as a hex string.
sha256_hash hash: The SHA256 hash of the certificate as a hex string.

tls::connection channel

Returns the current connection status of an SSL channel. The result is a list +of key-value pairs describing the connection. Returned values include:

+

SSL Status

+

state state: State of the connection.
servername name: The name of the connected to server.
protocol version: The protocol version used for the connection: SSL2, SSL3, TLS1, TLS1.1, TLS1.2, TLS1.3, or unknown.
renegotiation_allowed boolean: Whether protocol renegotiation is supported or not.
security_level level: The security level used for selection of ciphers, key size, etc.
session_reused boolean: Whether the session has been reused or not.
is_server boolean: Whether the connection is configured as a server (1) or client (0).
compression mode: Compression method.
expansion mode: Expansion method.
caList list: List of Certificate Authorities (CA) for X.509 certificate.

+

Cipher Info

+

cipher cipher: The current cipher in use for the connection.
standard_name name: The standard RFC name of cipher.
algorithm_bits n: The number of processed bits used for cipher.
secret_bits n: The number of secret bits used for cipher.
min_version version: The minimum protocol version for cipher.
cipher_is_aead boolean: Whether the cipher is Authenticated Encryption with Associated Data (AEAD).
cipher_id id: The OpenSSL cipher id.
description string: A text description of the cipher.
handshake_digest boolean: Digest used during handshake.

+

Session Info

+

alpn protocol: The protocol selected after Application-Layer Protocol Negotiation (ALPN).
resumable boolean: Whether the session can be resumed or not.
start_time seconds: Time since session started in seconds since epoch.
timeout seconds: Max duration of session in seconds before time-out.
lifetime seconds: Session ticket lifetime hint in seconds.
session_id binary_string: Unique session id for use in resuming the session.
session_ticket binary_string: Unique session ticket for use in resuming the session.
ticket_app_data binary_string: Unique session ticket application data.
master_key binary_string: Unique session master key.
session_cache_mode mode: Server cache mode (client, server, or both).

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 the 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::protocols

Returns a list of the supported SSL/TLS 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.

+

Certificate Validation

+

Summary of command line options

+

The following options are used for peer Certificate Validation:

+

-cadir directory: Specifies the directory where the Certificate Authority (CA) certificates are +stored. The default is platform specific, but is usually "/etc/ssl/certs" on +Linux/Unix systems. The default location can be overridden by the +SSL_CERT_DIR environment variable.
-cafile filename: Specifies the file with the Certificate Authority (CA) certificates to use in +PEM file format. The default is "cert.pem", in the OpenSSL directory. On +Linux/Unix systems, this is usually "/etc/ssl/ca-bundle.pem". The default file +can be overridden by the SSL_CERT_FILE environment variable.
-castore URI: Specifies the Uniform Resource Identifier (URI) for the Certificate Authority +(CA) store, which may be a single container or a catalog of containers. +Starting with OpenSSL 3.2 on Windows, set to "org.openssl.winstore://" +to use the built-in Windows Certificate Store. This store only supports root +certificate stores.
-request bool: Request a certificate from peer during the SSL handshake. This is needed to do +Certificate Validation. Default is true. In addition, the +client can manually inspect and accept or reject each certificate using the +-validatecommand option.
-require bool: Require a valid certificate from peer during the SSL handshake. If this is set +to true, then -request must also be set to true and either +-cadir, -cafile, -castore, or a platform default must be +provided in order to validate against. The default is false since not +all platforms have certificates to validate against in a form compatible with +OpenSSL. See Certificate Validation for more details.

+

When are command line options needed?

+

By default, a client TLS connection does NOT validate the server certificate chain. This limitation is due to the lack of a common cross platform database of Certificate Authority (CA) provided certificates to validate against. Many Linux systems natively support OpenSSL and thus have these certificates installed as part of the OS, but MacOS and Windows do not. In -order to use the -require option, one of the following must be true:

-

On Linux and Unix systems with OpenSSL already installed, if the CA -certificates are stored in the standard locations, or the SSL_CERT_DIR -or SSL_CERT_FILE env vars are set, then no other options are needed.
If OpenSSL is not installed in the default location, or when using Mac OS -or Windows and OpenSSL is installed, the SSL_CERT_DIR and/or -SSL_CERT_FILE env vars or the -cadir and/or -cafile - options must be defined.
On Windows, starting in OpenSSL 3.2, it is now possible to access the +order to use the -require option, one of the following must be true:
+
- On Linux and Unix systems with OpenSSL already installed, if the CA +certificates are stored in the standard locations, or if the SSL_CERT_DIR +or SSL_CERT_FILE environment variables are set, then -cadir, +-cadir, and -castore aren't needed.
- If OpenSSL is not installed in the default location, or when using Mac OS +or Windows and OpenSSL is installed, the SSL_CERT_DIR and/or +SSL_CERT_FILE environment variables or the one of the -cadir, +-cadir, or -castore options must be defined.
- On Windows, starting in OpenSSL 3.2, it is now possible to access the built-in Windows Certificate Store from OpenSSL. This can be achieved by -setting the -castore option to "org.openssl.winstore://".
- If OpenSSL is not installed, the CA certificates must be downloaded and +setting the -castore option to "org.openssl.winstore://".
- If OpenSSL is not installed, the CA certificates must be downloaded and installed with the user software. The CURL team makes them available at CA certificates extracted -from Mozilla in the cacert.pem file. You must then either -set the SSL_CERT_DIR and/or SSL_CERT_FILE env vars or the --cadir or -cafile options to the CA cert file's install -location. It is your responsibility to keep this file up to date.
-
- -
- -
CALLBACK OPTIONS
- -
-As indicated above, individual channels can be given their own callbacks -to handle intermediate processing by the OpenSSL library, using the --command, -password, and --validate_command options passed to either of -tls::socket or tls::import. -Unlike previous versions of TCL TLS, only if the callback generates an error, -will the bgerror command will be invoked with the error information. -
- -
-
-command callback
-
- Invokes the specified callback script at several points - during the OpenSSL handshake and use. See below for the possible - arguments passed to the callback script. Values returned from the - callback are ignored. -
-
-
- error channelId message -
-
- This form of callback is invoked whenever an error occurs during the - initial connection, handshake, or I/O operations. The message - argument can be from the Tcl_ErrnoMsg, OpenSSL function - ERR_reason_error_string(), or a custom message. -
-
-
- info channelId major minor message type -
-
- This form of callback is invoked by the OpenSSL function - SSL_set_info_callback() during the initial connection - and handshake operations. The type argument is new for - TLS 1.8. The arguments are: -
-
-
Possible values for major are: - handshake, alert, connect, accept.
-
Possible values for minor are: - start, done, read, write, loop, exit.
-
The message argument is a descriptive string which may - be generated either by SSL_state_string_long() or by - SSL_alert_desc_string_long(), depending on the context.
-
For alerts, the possible values for type are: - warning, fatal, and unknown. For others, - info is used.
-
-
-
- message channelId direction version content_type message -
-
- This form of callback is invoked by the OpenSSL function - SSL_set_msg_callback() whenever a message is sent or - received during the initial connection, handshake, or I/O operations. - It is only available when OpenSSL is complied with the - enable-ssl-trace option. Arguments are: direction - is Sent or Received, version is the protocol - version, content_type is the message content type, and - message is more info from the SSL_trace API. - This callback is new for TLS 1.8. -
-
-
- session channelId session_id ticket lifetime -
-
- This form of callback is invoked by the OpenSSL function - SSL_CTX_sess_set_new_cb() whenever a new session id is - sent by the server during the initial connection and handshake, but - can also be received later if the -post_handshake option is - used. Arguments are: session_id is the current - session identifier, ticket is the session ticket info, and - lifetime is the the ticket lifetime in seconds. - This callback is new for TLS 1.8. -
-
-
-
-
-
-
-password callback
-
- Invokes the specified callback script when OpenSSL needs to - obtain a password. See below for the possible arguments passed to - the callback script. See below for valid return values. -
-
-
- password rwflag size -
-
- Invoked when loading or storing a PEM certificate with encryption. - Where rwflag is 0 for reading/decryption or 1 for - writing/encryption (can prompt user to confirm) and size is - the max password length in bytes. The callback should return the - password as a string. Both arguments are new for TLS 1.8. -
-
-
-
-
-
-
-validatecommand callback
-
- Invokes the specified callback script during handshake in - order to validate the provided value(s). See below for the possible - arguments passed to the callback script. If not specified, OpenSSL - will accept valid certificates and extensions. - To reject the value and abort the connection, the callback should return 0. - To accept the value and continue the connection, it should return 1. - To reject the value, but continue the connection, it should return 2. -
-
-
- alpn channelId protocol match -
-
- For servers, this form of callback is invoked when the client ALPN - extension is received. If match is true, protocol - is the first -alpn option specified protocol common to both - the client and server. If not, the first client specified protocol is - used. It is called after the hello and ALPN callbacks. - This callback is new for TLS 1.8. -
-
-
- hello channelId servername -
-
- For servers, this form of callback is invoked during client hello - message processing. The purpose is so the server can select the - appropriate certificate to present to the client, and to make other - configuration adjustments relevant to that server name and its - configuration. It is called before the SNI and ALPN callbacks. - This callback is new for TLS 1.8. -
-
-
- sni channelId servername -
-
- For servers, this form of callback is invoked when the Server Name - Indication (SNI) extension is received. The servername - argument is the client provided server name in the -servername - option. The purpose is so when a server supports multiple names, the - right certificate can be used. It is called after the hello callback - but before the ALPN callback. - This callback is new for TLS 1.8. -
-
-
- verify channelId depth cert status error -
-
- This form of callback is invoked by OpenSSL when a new certificate - is received from the peer. It allows the client to check the - certificate verification results and choose whether to continue - or not. It is called for each certificate in the certificate chain. -
-
The depth argument is the integer depth of the - certificate in the certificate chain, where 0 is the peer certificate - and higher values going up to the Certificate Authority (CA).
-
The cert argument is a list of key-value pairs similar - to those returned by - tls::status.
-
The status argument is the boolean validity of the - current certificate where 0 is invalid and 1 is valid.
-
The error argument is the error message, if any, generated - by X509_STORE_CTX_get_error().
-
-
-
-
-
-
- -
-Reference implementations of these callbacks are provided in the -distribution as tls::callback, tls::password, -and tls::validate_command respectively. Note that these are -sample implementations only. In a more realistic deployment -you would specify your own callback scripts on each TLS channel using the --command, -password, and --validate_command options. -
-
-The default behavior when the -command and -validate_command -options are not specified is for TLS to process the associated library callbacks -internally. The default behavior when the -password option is not -specified is for TLS to process the associated library callbacks by attempting -to call tls::password. -The difference between these two behaviors is a consequence of maintaining -compatibility with earlier implementations. -
-
- -The use of the reference callbacks tls::callback, -tls::password, and tls::validate_command -is not recommended. They may be removed from future releases. - -
-
- -
- -
DEBUG
- -
For most debugging needs, the -callback option can be used to provide -sufficient insight and information on the TLS handshake and progress. If further -troubleshooting insight is needed, the compile time option --enable-debug -can be used to get detailed execution flow status.
- -
TLS key logging can be enabled by setting the environment variable -SSLKEYLOGFILE to the name of the file to log to. Then whenever TLS -key material is generated or received it will be logged to the file. This -is useful for logging key data for network logging tools to use to -decrypt the data.
- -
The tls::debug variable provides some additional -control over these reference callbacks. Its value is zero by default. -Higher values produce more diagnostic output, and will also force the -verify method in tls::callback to accept the -certificate, even when it is invalid if the tls::validate_command -callback is used for the -validatecommand option.
- -
The use of the variable tls::debug is not recommended. -It may be removed from future releases.
- -
Debug Examples
- +from Mozilla in the "cacert.pem" file. You must then either set the +SSL_CERT_DIR and/or SSL_CERT_FILE environment variables or the +-cadir or -cafile options to the CA cert file's install +location. It is your responsibility to keep this file up to date.

+

Callback Options

+

As previously described, each channel can be given their own callbacks +to handle intermediate processing by the OpenSSL library, using the +-command, -password, and -validate_command options +passed to either of tls::socket or tls::import. +Unlike previous versions of TclTLS, only if the callback generates an error, +will the bgerror command be invoked with the error information.

+

Values for Command Callback

+

The callback for the -command option is invoked at several points during the +OpenSSL handshake and during routine operations. See below for the possible +arguments passed to the callback script. Values returned from the callback are +ignored.

+

error channelId message

This form of callback is invoked whenever an error occurs during the initial +connection, handshake, or I/O operations. The message argument can be +from the Tcl_ErrnoMsg, OpenSSL function ERR_reason_error_string(), +or a custom message. This callback is new for TclTLS 1.8.

info channelId major minor message type

This form of callback is invoked by the OpenSSL function +SSL_set_info_callback() during the initial connection and handshake +operations. The arguments are:

+

major: Major category for error. Valid enums are: handshake, alert, +connect, accept.
minor: Minor category for error. Valid enums are: start, done, read, +write, loop, exit.
message: Descriptive message string which may be generated either by +SSL_state_string_long() or SSL_alert_desc_string_long(), +depending on the context.
type: For alerts, the possible values are: warning, +fatal, and unknown. For others, info is used. +This argument is new for TclTLS 1.8.

message channelId direction version content_type message

This form of callback is invoked by the OpenSSL function +SSL_set_msg_callback() whenever a message is sent or received during the +initial connection, handshake, or I/O operations. It is only available when +OpenSSL is complied with the enable-ssl-trace option. This callback is +new for TclTLS 1.8. The arguments are:

+

direction: Direction is either Sent or Received.
version: Version is the protocol version.
content_type: Content type is the message content type.
message: Message is more info from the SSL_trace API. +This argument is new for TclTLS 1.8.

session channelId session_id session_ticket lifetime

This form of callback is invoked by the OpenSSL function +SSL_CTX_sess_set_new_cb() whenever a new session id is sent by the +server during the initial connection and handshake and also during the session +if the -post_handshake option is set to true. This callback is new for +TclTLS 1.8. The arguments are:

+

session_id: Session Id is the current session identifier
session_ticket: Ticket is the session ticket info
lifetime: Lifetime is the ticket lifetime in seconds.

verify channelId depth cert status error

This callback was moved to the -verify_callback in TclTLS 1.8.

+

Values for Password Callback

+

The callback for the -password option is invoked by TclTLS whenever OpenSSL needs +to obtain a password. See below for the possible arguments passed to the +callback script. The user provided password is expected to be returned by the +callback.

+

password rwflag size

Invoked when loading or storing an encrypted PEM certificate. The arguments are:

+

rwflag: The read/write flag is 0 for reading/decryption or 1 for writing/encryption. +The latter can be used to determine when to prompt the user to confirm. +This argument is new for TclTLS 1.8.
size: The size is the maximum length of the password in bytes. +This argument is new for TclTLS 1.8.

+

Values for Validate Command Callback

+

The callback for the -validatecommand option is invoked during the handshake +process in order for the application to validate the provided value(s). See +below for the possible arguments passed to the callback script. If not +specified, OpenSSL will accept all valid certificates and extensions. To reject +the value and abort the connection, the callback should return 0. To accept the +value and continue the connection, it should return 1. To reject the value, but +continue the connection, it should return 2. This callback is new for TclTLS 1.8.

+

alpn channelId protocol match

For servers, this form of callback is invoked when the client ALPN extension is +received. If match is true, then protocol is the first +-alpn protocol option in common to both the client and server. +If not, the first client specified protocol is used. This callback is called +after the Hello and ALPN callbacks.

hello channelId servername

For servers, this form of callback is invoked during client hello message +processing. The purpose is so the server can select the appropriate certificate +to present to the client, and to make other configuration adjustments relevant +to that server name and its configuration. It is called before the SNI and ALPN +callbacks.

sni channelId servername

For servers, this form of callback is invoked when the Server Name Indication +(SNI) extension is received. The servername argument is the client +provided server name specified in the -servername</b> option. The +purpose is so when a server supports multiple names, the right certificate +can be used. It is called after the hello callback but before the ALPN +callback.

verify channelId depth cert status error

This form of callback is invoked by OpenSSL when a new certificate is received +from the peer. It allows the client to check the certificate verification +results and choose whether to continue or not. It is called for each +certificate in the certificate chain. This callback was moved from +-command in TclTLS 1.8. The arguments are:

+

depth: The depth is the integer depth of the certificate in the certificate chain, +where 0 is the peer certificate and higher values going up to the Certificate +Authority (CA).
cert: The cert argument is a list of key-value pairs similar to those returned by +tls::status.
status: The status argument is the boolean validity of the current certificate where 0 +is invalid and 1 is valid.
error: The error argument is the error message, if any, generated by +X509_STORE_CTX_get_error().

+

Reference implementations of these callbacks are provided in "tls.tcl" +as tls::callback, tls::password, and tls::validate_command +respectively. Note that these are only sample implementations. In a more +realistic deployment you would specify your own callback scripts on each TLS +channel using the -command, -password, and +-validate_command options.

+

The default behavior when the -command and -validate_command +options are not specified, is for TclTLS to process the associated library +callbacks internally. The default behavior when the -password option +is not specified is for TclTLS to process the associated library callbacks by +attempting to call tls::password. The difference between these two +behaviors is a consequence of maintaining compatibility with earlier +implementations.

+

The use of the reference callbacks tls::callback, tls::password, +and tls::validate_command is not recommended. They may be removed from future releases.

+

Debug

+

For most debugging needs, the -callback option can be used to provide +sufficient insight and information on the TLS handshake and progress. If +further troubleshooting insight is needed, the compile time option +--enable-debug can be used to get detailed execution flow status.

+

TLS key logging can be enabled by setting the environment variable +SSLKEYLOGFILE to the name of the file to log to. Then whenever TLS key +material is generated or received it will be logged to the file. This is useful +for logging key data for network logging tools to use to decrypt the data.

+

The tls::debug variable provides some additional control over these +reference callbacks. Its value is zero by default. Higher values produce more +diagnostic output, and will also force the verify method in tls::callback +to accept the certificate, even when it is invalid if the +-validatecommand option is set to tls::validate_command.

+

The use of the variable tls::debug is not recommended. +It may be removed from future releases.

+

Debug Examples

These examples use the default Unix platform SSL certificates. For standard installations, -cadir and -cafile should not be needed. If your certificates are in non-standard locations, update -cadir or use -cafile as needed.

-
-

Example #1: Use HTTP package

-


+ package require http
 package require tls
-set url "https://www.tcl.tk/"
-
-http::register https 443 [list ::tls::socket -autoservername true -require true -cadir /etc/ssl/certs \
-    -command ::tls::callback -password ::tls::password -validatecommand ::tls::validate_command]
-
+set url "https://www.tcl.tk/"
+http::register https 443 [list ::tls::socket -autoservername true -require true -cadir /etc/ssl/certs  -command ::tls::callback -password ::tls::password -validatecommand ::tls::validate_command]
 # Check for error
 set token [http::geturl $url]
-if {[http::status $token] ne "ok"} {
-    puts [format "Error %s" [http::status $token]]
+if {[http::status $token] ne "ok"} {
+    puts [format "Error %s" [http::status $token]]
 }
-
 # Get web page
 set data [http::data $token]
 puts [string length $data]
-
 # Cleanup
 ::http::cleanup $token
-
-
+

Example #2: Use raw socket

-


+ package require tls
-
-set url "www.tcl-lang.org"
+set url "www.tcl-lang.org"
 set port 443
-
-set ch [tls::socket -autoservername 1 -servername $url -request 1 -require 1 \
-    -alpn {http/1.1} -cadir /etc/ssl/certs -command ::tls::callback \
-    -password ::tls::password -validatecommand ::tls::validate_command $url $port]
+set ch [tls::socket -autoservername 1 -servername $url -request 1 -require 1  -alpn {http/1.1} -cadir /etc/ssl/certs -command ::tls::callback  -password ::tls::password -validatecommand ::tls::validate_command $url $port]
 chan configure $ch -buffersize 65536
 tls::handshake $ch
-
-puts $ch "GET / HTTP/1.1"
+puts $ch "GET / HTTP/1.1"
 flush $ch
 after 500
 set data [read $ch]
-
 array set status [tls::status $ch]
 array set conn [tls::connection $ch]
 array set chan [chan configure $ch]
 close $ch
 parray status
 parray conn
 parray chan
-
-

-
-
-
-HTTPS EXAMPLE
-
+

+

HTTP Package Examples

These examples use the default Unix platform SSL certificates. For standard installations, -cadir and -cafile should not be needed. If your certificates -are in non-standard locations, update -cadir or use -cafile as needed.

- -

Example #1: Get web page

-


+are in non-standard locations, set -cadir or use -cafile as needed.
+Example #3: Get web page
+ package require http
 package require tls
-set url "https://www.tcl.tk/"
-
+set url "https://www.tcl.tk/"
 http::register https 443 [list ::tls::socket -autoservername true -require true -cadir /etc/ssl/certs]
-
 # Check for error
 set token [http::geturl $url]
-if {[http::status $token] ne "ok"} {
-    puts [format "Error %s" [http::status $token]]
+if {[http::status $token] ne "ok"} {
+    puts [format "Error %s" [http::status $token]]
 }
-
 # Get web page
 set data [http::data $token]
 puts $data
-
 # Cleanup
 ::http::cleanup $token
-
-
-Example #2: Download file
-
+

+Example #4: Download file
+ package require http
 package require tls
-
-set url "https://wiki.tcl-lang.org/sitemap.xml"
+set url "https://wiki.tcl-lang.org/sitemap.xml"
 set filename [file tail $url]
-
 http::register https 443 [list ::tls::socket -autoservername true -require true -cadir /etc/ssl/certs]
-
 # Get file
 set ch [open $filename wb]
 set token [::http::geturl $url -blocksize 65536 -channel $ch]
-
 # Cleanup
 close $ch
 ::http::cleanup $token
-
-

-
-
-
-SPECIAL CONSIDERATIONS
-
+

+

Special Considerations

The capabilities of this package can vary enormously based upon how the linked to OpenSSL library was configured and built. New versions may obsolete older protocol versions, add or remove ciphers, change default values, etc. -Use the tls::protocols commands to obtain the supported +Use the tls::protocols commands to obtain the supported protocol versions.

- -

KEYWORDS

- -

tls, I/O, IP Address, OpenSSL -SSL, TCP, TLS, asynchronous I/O, -bind, certificate, channel, connection, -domain name, host,https, network address, -network, socket, TclTLS -

- -

-Copyright © 1999 Matt Newman
-Copyright © 2004 Starfish Systems
-Copyright © 2023-2024 Brian O'Hagan
-

- - +

Keywords

+

I/O, IP Address, OpenSSL, SSL, TCP, TLS, TclTLS, asynchronous I/O, bind, certificate, channel, connection, domain name, host, https, network, network address, socket, tls

+

Copyright

+

TCL Tls Extension Documentation

NAME

SYNOPSIS

DESCRIPTION

tls(n) 1.8 tls "Tcl TLS extension"

Name

Table Of Contents

Synopsis

Description

COMMANDS

CERTIFICATE VALIDATION

Summary of command line options:

When are command line options needed:

Commands

Certificate Validation

Summary of command line options

When are command line options needed?

CALLBACK OPTIONS

DEBUG

Debug Examples

Callback Options

Values for Command Callback

Values for Password Callback

Values for Validate Command Callback

Debug

Debug Examples

HTTPS EXAMPLE

HTTP Package Examples

SPECIAL CONSIDERATIONS

Special Considerations

See Also

KEYWORDS

See Also

Keywords

Category

Copyright