Versions of HPCC Systems® platform prior to 6.0.0 have always allowed some control over which operations were permitted in ECL code. This was done, among other reasons, as a way to ensure that operations like PIPE or embedded C++ could not be used to circumvent access controls on files by reading them directly from the operating system.
Version 6.0.0 (and above) has two features to provide more flexibility over the control of these operations.
We now limit which SERVICE functions are called at compile time using the FOLD attribute. Typically, for security reasons , FOLD should only be enabled in signed modules.
You can configure the access rights (which control the ability to use PIPE, embed C++, or restrict the use of a SERVICE) to be dependent on the code being signed. This means that we can provide signed code in the ECL Standard Library that makes use of these features, without opening them up for anyone to call anything.
In Configuration Manager, the ECLCC Server component has a tab named Options. This tab allows you to enter name value pairs for permissions to execute various types of embedded code or plugins.
Name
| --allow | Allow the option specified. |
| --deny | Deny the option specified. |
| --allowsigned | Allow the option specified if the code has been signed and the key is present. |
Note: Parts of the Standard Library may not function if the use of C++ and external definitions is denied. In general, allowsigned is preferred.
Cluster
Specify the cluster for which this rule applies. If cluster is left blank, the restriction applies to all clusters in the environment.
Value
| cpp | Allow/Deny C++ and other embedded languages. For languages other than C++ and Cassandra, an optional plugin must also be installed |
| pipe | Allow/Deny using external applications using the PIPE command. |
| extern | Allow/Deny an external function (SERVICE) |
| datafile | (Valid only for --allowedsigned). This specifies that access to data is only allowed if the code has been signed and the key is present. |
Code signing is similar to the way that emails can be signed to prove that they are from who they say they are and they have not been tampered with, using the standard gpg package.
A file that has been signed will have an attached signature containing a cryptographic hash of the file contents with the signer's private key. Anyone in possession of the signer's public key can then verify that the signature is valid and that the content is unchanged.
We have signed the SERVICE definitions provided by the ECL standard plugins and included the public key in the HPCC Systems platform installation. Code that tries to use service definitions that are signed will continue to work as before but, code that tries to call arbitrary library functions using user-supplied SERVICE definitions will give compile errors, if the code is unsigned, and the extern setting (see above) is set to deny or allowsigned.
System administrators can install additional keys on the ECLCC Server machine, so if you want to use your own service definitions, they can be signed using a key that has been installed in this way:
gpg --output <signed-ecl> --default-key <key-id> --clearsign <ecl-file-to-sign>Using this method, a trusted person can sign code to indicate that it is acceptable for untrusted people to use, without allowing the untrusted people to execute arbitrary code.