MCP Atlassian: Insecure File Permissions on OAuth Token Storage

# src/mcp_atlassian/utils/oauth.py:402-403
token_dir = Path.home() / ".mcp-atlassian"
token_dir.mkdir(exist_ok=True)

# src/mcp_atlassian/utils/oauth.py:406-418
token_path = token_dir / f"oauth-{self.client_id}.json"

if token_data is None:
    token_data = {
        "refresh_token": self.refresh_token,
        "access_token": self.access_token,
        "expires_at": self.expires_at,
        "cloud_id": self.cloud_id,
        "base_url": self.base_url,
    }

with open(token_path, "w") as f:
    json.dump(token_data, f)

# Step 1: Victim runs mcp-atlassian with OAuth and completes the flow.
# This creates the token file.

# Step 2: As any other user on the same system, read the token file:
cat /home/victim/.mcp-atlassian/oauth-*.json

# Expected output (sensitive credentials in plaintext):
# {"refresh_token": "eyJ...", "access_token": "eyJ...", "expires_at": 1741234567.0, "cloud_id": "abc-123", "base_url": null}

# Step 3: Verify the token works:
curl -H "Authorization: Bearer <stolen_access_token>" \
  "https://api.atlassian.com/ex/jira/<stolen_cloud_id>/rest/api/3/myself"

# Step 4: Use the refresh token to get a new access token:
curl -X POST "https://auth.atlassian.com/oauth/token" \
  -d "grant_type=refresh_token" \
  -d "client_id=<from_env>" \
  -d "client_secret=<from_env>" \
  -d "refresh_token=<stolen_refresh_token>"

ls -la ~/.mcp-atlassian/
# drwxr-xr-x  2 user user 4096 Mar 10 12:00 .
# -rw-r--r--  1 user user  256 Mar 10 12:00 oauth-abc123.json
#                ^^ ^^ ^^
#                world-readable!

# src/mcp_atlassian/utils/oauth.py

import os
import stat

def _save_tokens_to_file(self, token_data: dict | None = None) -> None:
    """Save the tokens to a file as fallback storage."""
    try:
        token_dir = Path.home() / ".mcp-atlassian"
        token_dir.mkdir(exist_ok=True, mode=0o700)

        token_path = token_dir / f"oauth-{self.client_id}.json"

        if token_data is None:
            token_data = {
                "refresh_token": self.refresh_token,
                "access_token": self.access_token,
                "expires_at": self.expires_at,
                "cloud_id": self.cloud_id,
                "base_url": self.base_url,
            }

        # Open with restrictive permissions (owner-only read/write)
        fd = os.open(
            str(token_path),
            os.O_WRONLY | os.O_CREAT | os.O_TRUNC,
            stat.S_IRUSR | stat.S_IWUSR,  # 0o600
        )
        try:
            with os.fdopen(fd, "w") as f:
                json.dump(token_data, f)
        except Exception:
            os.close(fd)
            raise

        logger.debug(f"Saved OAuth tokens to file {token_path} (fallback storage)")
    except Exception as e:
        logger.error(f"Failed to save tokens to file: {e}")

# In __init__ or from_env, ensure existing directories are tightened
token_dir = Path.home() / ".mcp-atlassian"
if token_dir.exists():
    os.chmod(str(token_dir), 0o700)