Avoid using string parsing for ParameterExpression.sympify() #14391
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
In the recently merged Qiskit#13278 the implementation for the sympify method for ParameterExpression was changed because we no longer rely on symengine internally. Previously we would just return the inner symengine object used to represent the symbolic expression. Without symengine available Qiskit#13278 updated the implementation of the method to generate a string representation of the expression and pass that to sympify which has a "parser" for converting that expression string to a sympy object. However, sympify() method is insecure as it internally relies on Python's eval() to parse the string and can't be used for untrusted input. While this doesn't have the same exact exposure as in GHSA-6m2c-76ff-6vrf because you have to opt-in to using this function with input that is untrusted and the degrees of freedom are less because it has to go through the rust symbolic expression it is still a potential vulnerability waiting to happen. This commit reworks the sympify implementation to avoid using sympy's parser and instead just builds the sympy expression from the internal state directly.
|
One or more of the following people are relevant to this code:
|
Pull Request Test Coverage Report for Build 15165457978Warning: This coverage report may be inaccurate.This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.
Details
💛 - Coveralls |
Cryoris
reviewed
May 19, 2025
There was a problem hiding this comment.
This looks much cleaner than relying on sympify 👍🏻 Would it make sense to add some concrete test cases, or do you think this is sufficiently tested implicitly? Right now I think there's only a single test that calls sympify directly, and it's not comparing to a hardcoded SymPy expression.
|
I'll add some specific tests, there is definitely some coverage from template optimization. It caught some bugs, but I can reuse the circuits from the qpy tests and test |
|
Test added in: 39e360a it caught several issues with the implementation |
rahaman-quantum
pushed a commit
to rahaman-quantum/qiskit
that referenced
this pull request
Jun 20, 2025
…14391) * Avoid using string parsing for ParameterExpression.sympify() In the recently merged Qiskit#13278 the implementation for the sympify method for ParameterExpression was changed because we no longer rely on symengine internally. Previously we would just return the inner symengine object used to represent the symbolic expression. Without symengine available Qiskit#13278 updated the implementation of the method to generate a string representation of the expression and pass that to sympify which has a "parser" for converting that expression string to a sympy object. However, sympify() method is insecure as it internally relies on Python's eval() to parse the string and can't be used for untrusted input. While this doesn't have the same exact exposure as in GHSA-6m2c-76ff-6vrf because you have to opt-in to using this function with input that is untrusted and the degrees of freedom are less because it has to go through the rust symbolic expression it is still a potential vulnerability waiting to happen. This commit reworks the sympify implementation to avoid using sympy's parser and instead just builds the sympy expression from the internal state directly. * Remove unused Rust functions that support sympy string generation * Add test coverage for all of parameter expression * Add .sign() to the megaexpression
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Summary
In the recently merged #13278 the implementation for the sympify method for ParameterExpression was changed because we no longer rely on symengine internally. Previously we would just return the inner symengine object used to represent the symbolic expression. Without symengine available #13278 updated the implementation of the method to generate a string representation of the expression and pass that to sympify which has a "parser" for converting that expression string to a sympy object. However, sympify() method is insecure as it internally relies on Python's eval() to parse the string and can't be used for untrusted input. While this doesn't have the same exact exposure as in GHSA-6m2c-76ff-6vrf because you have to opt-in to using this function with input that is untrusted and the degrees of freedom are less because it has to go through the rust symbolic expression it is still a potential vulnerability waiting to happen. This commit reworks the sympify implementation to avoid using sympy's parser and instead just builds the sympy expression from the internal state directly.
Details and comments