228 lines
8.4 KiB
Python
228 lines
8.4 KiB
Python
"""Gemini-related features of the browser."""
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from pathlib import Path
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from bebop.browser.browser import Browser
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from bebop.command_line import CommandLine
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from bebop.fs import get_downloads_path
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from bebop.navigation import set_parameter
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from bebop.page import Page
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from bebop.protocol import Request, Response
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from bebop.tofu import trust_fingerprint, untrust_fingerprint, WRONG_FP_ALERT
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MAX_URL_LEN = 1024
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def open_gemini_url(browser: Browser, url, redirects=0, history=True,
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use_cache=True):
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"""Open a Gemini URL and set the formatted response as content.
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While the specification is not set in stone, every client takes a slightly
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different approach to enforcing TOFU. Read the `Request.connect` docs to
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find about cases where connection is aborted without asking the user. What
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interests us here is what happens when the user should decide herself? This
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happens in several cases, matching the request possible states. Here is
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what Bebop do (or want to do):
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- STATE_INVALID_CERT: the certificate has non-fatal issues; we may
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present the user the problems found and let her decide whether to trust
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temporarily the certificate or not BUT we currently do not parse the
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certificate's fields, so this state is never used.
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- STATE_UNKNOWN_CERT: the certificate is valid but has not been seen before;
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as we're doing TOFU here, we could automatically trust it or let the user
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choose. For simplicity, we always trust it permanently.
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Attributes:
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- browser: Browser object making the request.
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- url: a valid URL with Gemini scheme to open.
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- redirects: current amount of redirections done to open the initial URL.
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- history: if true, save the final URL to history.
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- use_cache: if true, look up if the page is cached before requesting it.
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"""
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if len(url) >= MAX_URL_LEN:
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browser.set_status_error("Request URL too long.")
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return
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browser.set_status(f"Loading {url}")
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if use_cache and url in browser.cache:
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browser.load_page(browser.cache[url])
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if browser.current_url and history:
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browser.history.push(browser.current_url)
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browser.current_url = url
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browser.set_status(url)
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return
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req = Request(url, browser.stash)
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connect_timeout = browser.config["connect_timeout"]
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connected = req.connect(connect_timeout)
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if not connected:
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if req.state == Request.STATE_ERROR_CERT:
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error = f"Certificate was missing or corrupt ({url})."
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elif req.state == Request.STATE_UNTRUSTED_CERT:
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_handle_untrusted_cert(browser, req)
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error = f"Certificate has been changed ({url})."
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elif req.state == Request.STATE_CONNECTION_FAILED:
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error_details = ": " + req.error if req.error else "."
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error = f"Connection failed ({url})" + error_details
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else:
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error = f"Connection failed ({url})."
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browser.set_status_error(error)
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return
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if req.state == Request.STATE_INVALID_CERT:
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pass
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elif req.state == Request.STATE_UNKNOWN_CERT:
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# Certificate is valid but unknown: trust it permanently.
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hostname = req.hostname
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fingerprint = req.cert_validation["hash"]
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trust_fingerprint(
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browser.stash,
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hostname,
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"SHA-512",
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fingerprint,
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trust_always=True
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)
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data = req.proceed()
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if not data:
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browser.set_status_error(f"Server did not respond in time ({url}).")
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return
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response = Response.parse(data)
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if not response:
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browser.set_status_error(f"Server response parsing failed ({url}).")
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return
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_handle_response(browser, response, url, redirects, history)
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def _handle_untrusted_cert(browser: Browser, request: Request):
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"""Handle a mismatch between known & server fingerprints.
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This function formats an alert page to explain to the user what the hell is
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going on and displays it.
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"""
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remote_fp = request.cert_validation["hash"]
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local_fp = request.cert_validation["saved_hash"]
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alert_page_source = WRONG_FP_ALERT.format(
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hostname=request.hostname,
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local_fp=local_fp,
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remote_fp=remote_fp,
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)
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alert_page = Page.from_gemtext(
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alert_page_source,
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browser.config["text_width"]
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)
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browser.load_page(alert_page)
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def _handle_response(browser: Browser, response: Response, url: str,
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redirects: int, history: bool):
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"""Handle a response from a Gemini server."""
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if response.code == 20:
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_handle_successful_response(browser, response, url, history)
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elif response.generic_code == 30 and response.meta:
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browser.open_url(response.meta, base_url=url, redirects=redirects + 1)
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elif response.generic_code in (40, 50):
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error = f"Server error: {response.meta or Response.code.name}"
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browser.set_status_error(error)
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elif response.generic_code == 10:
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_handle_input_request(browser, url, response.meta)
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else:
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error = f"Unhandled response code {response.code}"
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browser.set_status_error(error)
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def _handle_successful_response(browser: Browser, response: Response, url: str,
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history: bool):
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"""Handle a successful response content from a Gemini server.
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According to the MIME type received or inferred, the response is either
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rendered by the browser, or saved to disk. If an error occurs, the browser
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displays it.
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Only text content is rendered. For Gemini, the encoding specified in the
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response is used, if available on the Python distribution. For other text
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formats, only UTF-8 is attempted.
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Arguments:
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- browser: Browser instance that made the initial request.
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- url: original URL.
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- response: a successful Response.
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- history: whether to modify history on a page load.
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"""
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mime_type = response.get_mime_type()
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page = None
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error = None
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filepath = None
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if mime_type.main_type == "text":
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if mime_type.sub_type == "gemini":
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encoding = mime_type.charset
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try:
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text = response.content.decode(encoding, errors="replace")
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except LookupError:
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error = f"Unknown encoding {encoding}."
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else:
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page = Page.from_gemtext(text, browser.config["text_width"])
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else:
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text = response.content.decode("utf-8", errors="replace")
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page = Page.from_text(text)
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else:
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filepath = _get_download_path(url)
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if page:
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browser.load_page(page)
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if browser.current_url and history:
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browser.history.push(browser.current_url)
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browser.current_url = url
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browser.cache[url] = page
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browser.set_status(url)
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elif filepath:
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try:
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with open(filepath, "wb") as download_file:
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download_file.write(response.content)
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except OSError as exc:
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browser.set_status_error(f"Failed to save {url} ({exc})")
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else:
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browser.set_status(f"Downloaded {url} ({mime_type.short}).")
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elif error:
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browser.set_status_error(error)
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def _get_download_path(url: str) -> Path:
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"""Try to find the best download file path possible from this URL."""
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download_dir = get_downloads_path()
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url_parts = url.rsplit("/", maxsplit=1)
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if url_parts:
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filename = url_parts[-1]
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else:
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filename = url.split("://")[1] if "://" in url else url
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filename = filename.replace("/", "_")
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return download_dir / filename
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def _handle_input_request(browser: Browser, from_url: str, message: str =None):
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"""Focus command-line to pass input to the server."""
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if message:
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browser.set_status(f"Input needed: {message}")
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else:
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browser.set_status("Input needed:")
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user_input = browser.command_line.focus(CommandLine.CHAR_TEXT)
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if not user_input:
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return
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url = set_parameter(from_url, user_input)
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open_gemini_url(browser, url)
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def forget_certificate(browser: Browser, hostname: str):
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"""Remove the fingerprint associated to this hostname for the cert stash."""
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key = browser.prompt(f"Remove fingerprint from {hostname}? [y/N]", "ynN")
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if key != "y":
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browser.reset_status()
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return
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if untrust_fingerprint(browser.stash, hostname):
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browser.set_status(f"Known certificate for {hostname} removed.")
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else:
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browser.set_status_error(f"Known certificate for {hostname} not found.")
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