Adds commit classification rule (#397)

This PR adds a new rule using the `LLMService`.

It sends the diff of a commit to the LLM and asks if this commit is
security relevant or not. Relevance of the rule is set to 32 for now,
but this value can be adjusted after evaluation.

Thanks to @tommasoaiello

prospector/llm/llm_service.py

@@ -3,9 +3,11 @@
 import validators
 from langchain_core.language_models.llms import LLM
 from langchain_core.output_parsers import StrOutputParser
+from requests import HTTPError
 
 from llm.instantiation import create_model_instance
-from llm.prompts import prompt_best_guess
+from llm.prompts.classify_commit import zero_shot as cc_zero_shot
+from llm.prompts.get_repository_url import prompt_best_guess
 from log.logger import logger
 from util.config_parser import LLMServiceConfig
 from util.singleton import Singleton
@@ -74,3 +76,53 @@ def get_repository_url(self, advisory_description, advisory_references) -> str:
             raise RuntimeError(f"Prompt-model chain could not be invoked: {e}")
 
         return url
+
+    def classify_commit(
+        self, diff: str, repository_name: str, commit_message: str
+    ) -> bool:
+        """Ask an LLM whether a commit is security relevant or not. The response will be either True or False.
+
+        Args:
+            candidate (Commit): The commit to input into the LLM
+
+        Returns:
+            True if the commit is deemed security relevant, False if not.
+
+        Raises:
+            ValueError if there is an error in the model invocation or the response was not valid.
+        """
+        try:
+            chain = cc_zero_shot | self.model | StrOutputParser()
+
+            is_relevant = chain.invoke(
+                {
+                    "diff": diff,
+                    "repository_name": repository_name,
+                    "commit_message": commit_message,
+                }
+            )
+            logger.info(f"LLM returned is_relevant={is_relevant}")
+
+        except HTTPError as e:
+            # if the diff is too big, a 400 error is returned -> silently ignore by returning False for this commit
+            status_code = e.response.status_code
+            if status_code == 400:
+                return False
+            raise RuntimeError(f"Prompt-model chain could not be invoked: {e}")
+        except Exception as e:
+            raise RuntimeError(f"Prompt-model chain could not be invoked: {e}")
+
+        if is_relevant in [
+            "True",
+            "ANSWER:True",
+            "```ANSWER:True```",
+        ]:
+            return True
+        elif is_relevant in [
+            "False",
+            "ANSWER:False",
+            "```ANSWER:False```",
+        ]:
+            return False
+        else:
+            raise RuntimeError(f"The model returned an invalid response: {is_relevant}")

prospector/llm/prompts/classify_commit.py

@@ -0,0 +1,16 @@
+from langchain.prompts import PromptTemplate
+
+zero_shot = PromptTemplate.from_template(
+    """Is the following commit security relevant or not?
+Please provide the output as a boolean value, either True or False.
+If it is security relevant just answer True otherwise answer False. Do not return anything else.
+
+To provide you with some context, the name of the repository is: {repository_name}, and the
+commit message is: {commit_message}.
+
+Finally, here is the diff of the commit:
+{diff}\n
+
+
+Your answer:\n"""
+)

prospector/rules/rules.py

@@ -413,6 +413,18 @@ def apply(self, candidate: Commit, advisory_record: AdvisoryRecord):
         return False
 
 
+class CommitIsSecurityRelevant(Rule):
+    """Matches commits that are deemed security relevant by the commit classification service."""
+
+    def apply(
+        self,
+        candidate: Commit,
+    ) -> bool:
+        return LLMService().classify_commit(
+            candidate.diff, candidate.repository, candidate.message
+        )
+
+
 RULES_PHASE_1: List[Rule] = [
     VulnIdInMessage("VULN_ID_IN_MESSAGE", 64),
     # CommitMentionedInAdv("COMMIT_IN_ADVISORY", 64),
@@ -433,4 +445,6 @@ def apply(self, candidate: Commit, advisory_record: AdvisoryRecord):
     CommitHasTwins("COMMIT_HAS_TWINS", 2),
 ]
 
-RULES_PHASE_2: List[Rule] = []
+RULES_PHASE_2: List[Rule] = [
+    CommitIsSecurityRelevant("COMMIT_IS_SECURITY_RELEVANT", 32)
+]

prospector/rules/rules_test.py

@@ -89,7 +89,9 @@ def candidates():
             changed_files={
                 "core/src/main/java/org/apache/cxf/workqueue/AutomaticWorkQueueImpl.java"
             },
-            minhash=get_encoded_minhash(get_msg("Insecure deserialization", 50)),
+            minhash=get_encoded_minhash(
+                get_msg("Insecure deserialization", 50)
+            ),
         ),
         # TODO: Not matched by existing tests: GHSecurityAdvInMessage, ReferencesBug, ChangesRelevantCode, TwinMentionedInAdv, VulnIdInLinkedIssue, SecurityKeywordInLinkedGhIssue, SecurityKeywordInLinkedBug, CrossReferencedBug, CrossReferencedGh, CommitHasTwins, ChangesRelevantFiles, CommitMentionedInAdv, RelevantWordsInMessage
     ]
@@ -109,37 +111,47 @@ def advisory_record():
     )
 
 
-def test_apply_phase_1_rules(candidates: List[Commit], advisory_record: AdvisoryRecord):
+def test_apply_phase_1_rules(
+    candidates: List[Commit], advisory_record: AdvisoryRecord
+):
     annotated_candidates = apply_rules(
         candidates, advisory_record, enabled_rules=enabled_rules_from_config
     )
 
     # Repo 5: Should match: AdvKeywordsInFiles, SecurityKeywordsInMsg, CommitMentionedInReference
     assert len(annotated_candidates[0].matched_rules) == 3
 
-    matched_rules_names = [item["id"] for item in annotated_candidates[0].matched_rules]
+    matched_rules_names = [
+        item["id"] for item in annotated_candidates[0].matched_rules
+    ]
     assert "ADV_KEYWORDS_IN_FILES" in matched_rules_names
     assert "COMMIT_IN_REFERENCE" in matched_rules_names
     assert "SEC_KEYWORDS_IN_MESSAGE" in matched_rules_names
 
     # Repo 1: Should match: VulnIdInMessage, ReferencesGhIssue
     assert len(annotated_candidates[1].matched_rules) == 2
 
-    matched_rules_names = [item["id"] for item in annotated_candidates[1].matched_rules]
+    matched_rules_names = [
+        item["id"] for item in annotated_candidates[1].matched_rules
+    ]
     assert "VULN_ID_IN_MESSAGE" in matched_rules_names
     assert "GITHUB_ISSUE_IN_MESSAGE" in matched_rules_names
 
     # Repo 3: Should match: VulnIdInMessage, ReferencesGhIssue
     assert len(annotated_candidates[2].matched_rules) == 2
 
-    matched_rules_names = [item["id"] for item in annotated_candidates[2].matched_rules]
+    matched_rules_names = [
+        item["id"] for item in annotated_candidates[2].matched_rules
+    ]
     assert "VULN_ID_IN_MESSAGE" in matched_rules_names
     assert "GITHUB_ISSUE_IN_MESSAGE" in matched_rules_names
 
     # Repo 4: Should match: SecurityKeywordsInMsg
     assert len(annotated_candidates[3].matched_rules) == 1
 
-    matched_rules_names = [item["id"] for item in annotated_candidates[3].matched_rules]
+    matched_rules_names = [
+        item["id"] for item in annotated_candidates[3].matched_rules
+    ]
     assert "SEC_KEYWORDS_IN_MESSAGE" in matched_rules_names
 
     # Repo 2: Matches nothing