{"record":{"id":"0afd206c7af7e41d","repo":"trailofbits/algo","slug":"failed-to-derive-public-key-e","errorCode":null,"errorMessage":"Failed to derive public key: {e}","messagePattern":"Failed to derive public key: (.+?)","errorType":"exception","errorClass":null,"httpStatus":null,"severity":"error","filePath":"library/x25519_pubkey.py","lineNumber":121,"sourceCode":"\n            try:\n                with open(pub_path) as f:\n                    existing = f.read().strip()\n            except OSError:\n                existing = None\n\n            if existing != pub_b64:\n                try:\n                    with open(pub_path, \"w\") as f:\n                        f.write(pub_b64)\n                    result[\"changed\"] = True\n                except OSError as e:\n                    module.fail_json(msg=f\"Failed to write public key file: {e}\")\n\n            result[\"public_key_path\"] = pub_path\n\n    except Exception as e:\n        module.fail_json(msg=f\"Failed to derive public key: {e}\")\n\n    module.exit_json(**result)\n\n\ndef main():\n    \"\"\"Entry point when module is executed directly.\"\"\"\n    run_module()\n\n\nif __name__ == \"__main__\":\n    main()\n","sourceCodeStart":103,"sourceCodeEnd":133,"githubUrl":"https://github.com/trailofbits/algo/blob/20e22a8715c198b38c01c1ca62d0953b93587a74/library/x25519_pubkey.py#L103-L133","documentation":"A catch-all: any unexpected exception during public-key derivation or the surrounding logic (after the specific OSError branches) is converted to this message with the exception text. Common causes are failures inside cryptography's X25519PrivateKey.from_private_bytes or errors in the comparison/write logic not covered above.","triggerScenarios":"A non-32-byte key slipping past earlier checks raising ValueError in from_private_bytes, a pub_path that points at a directory (IsADirectoryError in the existing-file comparison), or any bug in the derived-key handling code.","commonSituations":"Edge-case key material, unexpected filesystem entries at pub_path, or version mismatches in the cryptography library.","solutions":["Re-run with -vvv to get the full exception text embedded in the message","Verify pub_path is a file path, not an existing directory","Confirm the cryptography package version supports X25519 (any modern version)","If it's an environment issue, regenerate the key pair in a clean environment"],"exampleFix":null,"handlingStrategy":"try-catch","validationCode":null,"typeGuard":null,"tryCatchPattern":"try:\n    pub_b64 = derive(pub_path, priv_path)\nexcept Exception as e:\n    logger.error('derivation failed: %s', e)\n    raise","preventionTips":["Run with -vvv to capture the embedded exception text","Validate inputs (32-byte key, writable paths) before calling the module","Pin the cryptography library version in the environment"],"tags":["x25519","ansible","unexpected-exception"],"backgroundTag":"unexpected-library-exception","analyzedSha":"20e22a8715c198b38c01c1ca62d0953b93587a74","analyzedAt":"2026-08-28T13:26:02.752Z","schemaVersion":2},"datasetVersion":"2026-08-28T16:17:29.566Z"}