"""Gemini-related features of the browser.""" import logging from typing import Optional from bebop.browser.browser import Browser from bebop.command_line import CommandLine from bebop.downloads import get_download_path from bebop.fs import get_identities_list_path from bebop.identity import ( ClientCertificateException, create_certificate, get_cert_and_key, get_identities_for_url, load_identities, save_identities ) from bebop.navigation import set_parameter from bebop.page import Page from bebop.preferences import get_url_render_mode_pref from bebop.protocol import Request, Response from bebop.tofu import trust_fingerprint, untrust_fingerprint, WRONG_FP_ALERT MAX_URL_LEN = 1024 def open_gemini_url( browser: Browser, url: str, redirects: int =0, use_cache: bool =False, cert_and_key=None ) -> Optional[str]: """Open a Gemini URL and set the formatted response as content. While the specification is not set in stone, every client takes a slightly different approach to enforcing TOFU. Read the `Request.connect` docs to find about cases where connection is aborted without asking the user. What interests us here is what happens when the user should decide herself? This happens in several cases, matching the request possible states. Here is what Bebop do (or want to do): - STATE_INVALID_CERT: the certificate has non-fatal issues; we may present the user the problems found and let her decide whether to trust temporarily the certificate or not BUT we currently do not parse the certificate's fields, not even the pubkey, so this state is never used. - STATE_UNKNOWN_CERT: the certificate is valid but has not been seen before; as we're doing TOFU here, we could automatically trust it or let the user choose. For simplicity, we always trust it permanently. Arguments: - browser: Browser object making the request. - url: a valid URL with Gemini scheme to open. - redirects: current amount of redirections done to open the initial URL. - use_cache: if true, look up if the page is cached before requesting it. - cert_and_key: if not None, a tuple of paths to a client cert/key to use. Returns: The final successfully handled URL on success, None otherwise. Redirected URLs are not returned. """ if len(url) >= MAX_URL_LEN: browser.set_status_error("Request URL too long.") return None loading_message_verb = "Loading" if redirects == 0 else "Redirecting to" loading_message = f"{loading_message_verb} {url}…" browser.set_status(loading_message) # If this URL used to request an identity, provide it. if not cert_and_key: url_identities = get_identities_for_url(browser.identities, url) identity = select_identity(url_identities) if identity: cert_and_key = get_cert_and_key(identity["id"]) if use_cache and url in browser.cache: browser.load_page(browser.cache[url]) browser.current_url = url return url logging.info( f"Request {url}" + (f" using cert and key {cert_and_key}" if cert_and_key else "") ) req = Request(url, browser.stash, identity=cert_and_key) connect_timeout = browser.config["connect_timeout"] connected = req.connect(connect_timeout) if not connected: if req.state == Request.STATE_ERROR_CERT: error = f"Certificate was missing or corrupt ({url})." elif req.state == Request.STATE_UNTRUSTED_CERT: _handle_untrusted_cert(browser, req) error = f"Certificate has been changed ({url})." elif req.state == Request.STATE_CONNECTION_FAILED: error_details = ": " + req.error if req.error else "." error = f"Connection failed ({url})" + error_details else: error = f"Connection failed ({url})." browser.set_status_error(error) return None if req.state == Request.STATE_INVALID_CERT: pass elif req.state == Request.STATE_UNKNOWN_CERT: # Certificate is valid but unknown: trust it permanently. hostname = req.hostname fingerprint = req.cert_validation["hash"] trust_fingerprint( browser.stash, hostname, "SHA-512", fingerprint, trust_always=True ) data = req.proceed() if not data: browser.set_status_error(f"Server did not respond in time ({url}).") return None response = Response.parse(data) if not response: browser.set_status_error(f"Server response parsing failed ({url}).") return None return _handle_response(browser, response, url, redirects) def _handle_untrusted_cert(browser: Browser, request: Request): """Handle a mismatch between known & server fingerprints. This function formats an alert page to explain to the user what the hell is going on and displays it. """ remote_fp = request.cert_validation["hash"] local_fp = request.cert_validation["saved_hash"] alert_page_source = WRONG_FP_ALERT.format( hostname=request.hostname, local_fp=local_fp, remote_fp=remote_fp, ) alert_page = Page.from_gemtext( alert_page_source, browser.config["text_width"] ) browser.load_page(alert_page) def _handle_response( browser: Browser, response: Response, url: str, redirects: int ) -> Optional[str]: """Handle a response from a Gemini server. Returns: The final URL on success, None otherwise. """ logging.info(f"Response {response.code} {response.meta}") if response.code == 20: return _handle_successful_response(browser, response, url) elif response.generic_code == 30 and response.meta: # On redirections, we go back to open_url as the redirection may be to # another protocol. Discard the result of this request. browser.open_url( response.meta, base_url=url, redirects=redirects + 1 ) elif response.generic_code in (40, 50): error = f"Server error: {response.meta or Response.code.name}" browser.set_status_error(error) elif response.generic_code == 10: return _handle_input_request(browser, url, response.meta) elif response.code == 60: return _handle_cert_required(browser, response, url, redirects) elif response.code in (61, 62): details = response.meta or Response.code.name error = f"Client certificate error: {details}" browser.set_status_error(error) else: error = f"Unhandled response code {response.code}" browser.set_status_error(error) return None def _handle_successful_response(browser: Browser, response: Response, url: str): """Handle a successful response content from a Gemini server. According to the MIME type received or inferred, the response is either rendered by the browser, or saved to disk. If an error occurs, the browser displays it. Only text content is rendered. For Gemini, the encoding specified in the response is used, if available on the Python distribution. For other text formats, only UTF-8 is attempted. Arguments: - browser: Browser instance that made the initial request. - url: original URL. - response: a successful Response. Returns: The successfully handled URL on success, None otherwise. """ # Use appropriate response parser according to the MIME type. mime_type = response.get_mime_type() page = None error = None filepath = None if mime_type.main_type == "text": if mime_type.sub_type == "gemini": encoding = mime_type.charset try: text = response.content.decode(encoding, errors="replace") except LookupError: error = f"Unknown encoding {encoding}." else: text_width = browser.config["text_width"] render_mode = get_url_render_mode_pref( browser.capsule_prefs, url, browser.config["render_mode"] ) page = Page.from_gemtext(text, text_width, render=render_mode) else: encoding = "utf-8" text = response.content.decode(encoding, errors="replace") page = Page.from_text(text) if page: page.mime = mime_type page.encoding = encoding else: download_dir = browser.config["download_path"] filepath = get_download_path(url, download_dir=download_dir) # If a page has been produced, load it. Else if a file has been retrieved, # download it. if page: browser.load_page(page) browser.current_url = url browser.cache[url] = page return url elif filepath: try: with open(filepath, "wb") as download_file: download_file.write(response.content) except OSError as exc: browser.set_status_error(f"Failed to save {url} ({exc})") else: browser.set_status(f"Downloaded {url} ({mime_type.short}).") browser.last_download = mime_type, filepath return url elif error: browser.set_status_error(error) return None def _handle_input_request( browser: Browser, from_url: str, message: str =None ) -> Optional[str]: """Focus command-line to pass input to the server. Returns: The result of `open_gemini_url` with the new request including user input. """ if message: browser.set_status(f"Input needed: {message}") else: browser.set_status("Input needed:") user_input = browser.command_line.focus(CommandLine.CHAR_TEXT) if not user_input: return url = set_parameter(from_url, user_input) return open_gemini_url(browser, url) def _handle_cert_required( browser: Browser, response: Response, url: str, redirects: int ) -> Optional[str]: """Find a matching identity and resend the request with it. Returns: The result of `open_gemini_url` with the client certificate provided. """ identities = load_identities(get_identities_list_path()) if identities is None: browser.set_status_error("Can't load identities.") return None browser.identities = identities url_identities = get_identities_for_url(browser.identities, url) if not url_identities: identity = create_identity(browser, url) if not identity: return None browser.identities[url] = [identity] save_identities(browser.identities, get_identities_list_path()) else: identity = select_identity(url_identities) cert_path, key_path = get_cert_and_key(identity["id"]) return open_gemini_url( browser, url, redirects=redirects + 1, cert_and_key=(cert_path, key_path) ) def select_identity(identities: list): """Let user select the appropriate identity among candidates.""" # TODO support multiple identities; for now we just use the first available. return identities[0] if identities else None def create_identity(browser: Browser, url: str): """Walk the user through identity creation. Returns: The created identity on success (already registered in identities """ key = browser.prompt("Create client certificate?") if key != "y": browser.reset_status() return None common_name = browser.get_user_text_input( "Name? The server will see this, you can leave it empty.", CommandLine.CHAR_TEXT, strip=True, ) if not common_name: browser.reset_status() return None browser.set_status("Generating certificate…") gen_command = browser.config["generate_client_cert_command"] try: mangled_name = create_certificate(url, common_name, gen_command) except ClientCertificateException as exc: browser.set_status_error(exc.message) return None browser.reset_status() return {"name": common_name, "id": mangled_name} def forget_certificate(browser: Browser, hostname: str): """Remove the fingerprint associated to this hostname for the cert stash.""" key = browser.prompt(f"Remove fingerprint for {hostname}?") if key != "y": browser.reset_status() return if untrust_fingerprint(browser.stash, hostname): browser.set_status(f"Known certificate for {hostname} removed.") else: browser.set_status_error(f"Known certificate for {hostname} not found.")