fix: prevent SQL injection in SnowflakeSearchTool and NL2SQLTool

[devin-ai-integration]

Summary

Fixes #4993 — SQL injection vulnerability in SnowflakeSearchTool via database and snowflake_schema parameters, and second-order SQL injection in NL2SQLTool via table_name in _fetch_all_available_columns.

SnowflakeSearchTool (snowflake_search_tool.py):

• Added pattern=r"^[A-Za-z_][A-Za-z0-9_$]*$" to database and snowflake_schema fields on SnowflakeSearchToolInput (Pydantic schema-level validation)
• Added _validate_identifier() runtime check in _run() as defense-in-depth
• Double-quoted identifiers in USE DATABASE / USE SCHEMA SQL statements

NL2SQLTool (nl2sql_tool.py):

• Added _validate_identifier() to sanitize table_name before f-string interpolation in _fetch_all_available_columns()

Both use the same regex matching Snowflake's unquoted identifier rules: must start with a letter or underscore, followed by alphanumerics, underscores, or $.

Review & Testing Checklist for Human

• Regex strictness: The pattern ^[A-Za-z_][A-Za-z0-9_$]*$ rejects dot-separated identifiers (e.g. db.schema) and hyphenated names. Verify this is acceptable for standalone database/schema/table name fields — should not be an issue since these are single identifiers, but confirm against real Snowflake usage.
• Duplicated _validate_identifier: The identical static method exists in both SnowflakeSearchTool and NL2SQLTool. Decide if this should be extracted to a shared utility.
• query parameter remains unsanitized: By design (the tool's purpose is to execute SQL), but confirm this trade-off is acceptable.

Notes

• The # noqa: S608 on nl2sql_tool.py:57 is preserved — the f-string interpolation remains but is now gated behind validation.
• The pre-existing test_cleanup_on_deletion test in the Snowflake test file was already failing before this PR (async context manager on threading.Lock) — not related to these changes.

Link to Devin session: https://app.devin.ai/sessions/c92ac82a6bb44a8889173bbdd664acee

[devin-ai-integration]

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[devin-ai-integration]

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