Implement C package: Declarations8

[knewbury01]

Description

Decl8

Change request type

• Release or process automation (GitHub workflows, internal scripts)
• Internal documentation
• External documentation
• Query files (.ql, .qll, .qls or unit tests)
• External scripts (analysis report or other code shipped as part of a release)

Rules with added or modified queries

• No rules added
• Queries have been added for the following rules:
  • DCL30-C
• Queries have been modified for the following rules:
  • rule number here

Release change checklist

A change note (development_handbook.md#change-notes) is required for any pull request which modifies:

• The structure or layout of the release artifacts.
• The evaluation performance (memory, execution time) of an existing query.
• The results of an existing query in any circumstance.

If you are only adding new rule queries, a change note is not required.

Author: Is a change note required?

• Yes
• No

🚨🚨🚨
Reviewer: Confirm that format of shared queries (not the .qll file, the
.ql file that imports it) is valid by running them within VS Code.

• Confirmed

Reviewer: Confirm that either a change note is not required or the change note is required and has been added.

• Confirmed

Query development review checklist

For PRs that add new queries or modify existing queries, the following checklist should be completed by both the author and reviewer:

Author

• Have all the relevant rule package description files been checked in?
• Have you verified that the metadata properties of each new query is set appropriately?
• Do all the unit tests contain both "COMPLIANT" and "NON_COMPLIANT" cases?
• Are the alert messages properly formatted and consistent with the style guide?
• Have you run the queries on OpenPilot and verified that the performance and results are acceptable?
  As a rule of thumb, predicates specific to the query should take no more than 1 minute, and for simple queries be under 10 seconds. If this is not the case, this should be highlighted and agreed in the code review process.
• Does the query have an appropriate level of in-query comments/documentation?
• Have you considered/identified possible edge cases?
• Does the query not reinvent features in the standard library?
• Can the query be simplified further (not golfed!)

Reviewer

• Have all the relevant rule package description files been checked in?
• Have you verified that the metadata properties of each new query is set appropriately?
• Do all the unit tests contain both "COMPLIANT" and "NON_COMPLIANT" cases?
• Are the alert messages properly formatted and consistent with the style guide?
• Have you run the queries on OpenPilot and verified that the performance and results are acceptable?
  As a rule of thumb, predicates specific to the query should take no more than 1 minute, and for simple queries be under 10 seconds. If this is not the case, this should be highlighted and agreed in the code review process.
• Does the query have an appropriate level of in-query comments/documentation?
• Have you considered/identified possible edge cases?
• Does the query not reinvent features in the standard library?
• Can the query be simplified further (not golfed!)

[knewbury01]

Notes DCL30-C

I chose to implement a specific subset of cases for this rule, as opposed to the general title/description of the rule. The examples in the wiki only describe the cases that I chose to cover and the tool comparison part of the wiki/logistics details described confirm that handling more general cases is a more difficult problem

This query was very close to several pre-existing queries...

1. the C++ rule M7-5-1 covers one specific part of the cases that I chose to cover (however C does not have references so I opted to write one query to unify the cases and omit the unnecessary reference bits)
2. the out of the box queries - ReturnStackAllocatedMemory and StackAddressEscapes also cover pretty similar scenarios, however as I said, I chose to unify the results into one query and additionally StackAddressEscapes has the same FP that my version does so I think maybe the results are not too different?

possible expansions

if it seems necessary for this query to cover more of the ways that storage durations can conflict or lead to undefined behaviour , possibly this query for thread storage durations could be a shared query split for the thread case specifically

[lcartey]

There is actually an even closer shared query we've written: DoNotCopyAddressOfAutoStorageObjectToOtherObject.qll

This is used in:

• M7-5-2 AssignmentOfEscapingAutoStorage.ql
• Rule 18.6 AutomaticStorageObjectAddressCopiedToOtherObject.ql

I think the query you've written covers essentially the same topics, so I think I would recommend replacing your query with an import query for the same library. The shared query could be extended if it doesn't cover all the cases (return statements?).

[knewbury01]

There is actually an even closer shared query we've written: DoNotCopyAddressOfAutoStorageObjectToOtherObject.qll

This is used in:

• M7-5-2 AssignmentOfEscapingAutoStorage.ql
• Rule 18.6 AutomaticStorageObjectAddressCopiedToOtherObject.ql

I think the query you've written covers essentially the same topics, so I think I would recommend replacing your query with an import query for the same library. The shared query could be extended if it doesn't cover all the cases (return statements?).

@lcartey, thanks for the review! I took a look,

I think DCL30-C == M7-5-1 + M7-5-2 (this one is actually using the out of the box equivalent for stack addresses that I found, but is the refined for our purposes version, so thank you for the much better find!)

I have now split and use the shared lib for the M7-5-2 part

however now that I look at the M7-5-1 implementation , I still think that maybe my version of it makes more sense for C (omitting the references stuff and using dataflow instead of not), unless you think that both need an update?

[lcartey]

Just some minor stylistic comments, otherwise looks good to me!