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369 lines
13 KiB
369 lines
13 KiB
"""Gemini-related features of the browser."""
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import logging
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from pathlib import Path
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from typing import Optional
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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 (
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get_downloads_path, get_identities_path, get_identities_list_path
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)
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from bebop.identity import (
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ClientCertificateException, create_certificate, get_cert_and_key,
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get_identities_for_url, load_identities, save_identities
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)
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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(
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browser: Browser,
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url: str,
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redirects: int =0,
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use_cache: bool =True,
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cert_and_key=None
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) -> Optional[str]:
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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, not even the pubkey, 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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Arguments:
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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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- use_cache: if true, look up if the page is cached before requesting it.
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- cert_and_key: if not None, a tuple of paths to a client cert/key to use.
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Returns:
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The final successfully handled URL on success, None otherwise. Redirected
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URLs are not returned.
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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 None
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loading_message_verb = "Loading" if redirects == 0 else "Redirecting to"
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loading_message = f"{loading_message_verb} {url}…"
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browser.set_status(loading_message)
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# If this URL used to request an identity, provide it.
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if not cert_and_key:
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url_identities = get_identities_for_url(browser.identities, url)
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identity = select_identity(url_identities)
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if identity:
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cert_and_key = get_cert_and_key(identity["id"])
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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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browser.current_url = url
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browser.set_status(url)
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return url
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logging.info(
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f"Request {url}"
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+ (f" using cert and key {cert_and_key}" if cert_and_key else "")
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)
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req = Request(url, browser.stash, identity=cert_and_key)
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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 None
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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 None
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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 None
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return _handle_response(browser, response, url, redirects)
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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(
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browser: Browser,
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response: Response,
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url: str,
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redirects: int
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) -> Optional[str]:
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"""Handle a response from a Gemini server.
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Returns:
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The final URL on success, None otherwise.
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"""
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logging.info(f"Response {response.code} {response.meta}")
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if response.code == 20:
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return _handle_successful_response(browser, response, url)
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elif response.generic_code == 30 and response.meta:
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# On redirections, we go back to open_url as the redirection may be to
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# another protocol. Discard the result of this request.
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browser.open_url(
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response.meta,
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base_url=url,
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redirects=redirects + 1
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)
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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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return _handle_input_request(browser, url, response.meta)
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elif response.code == 60:
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return _handle_cert_required(browser, response, url, redirects)
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elif response.code in (61, 62):
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details = response.meta or Response.code.name
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error = f"Client certificate error: {details}"
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browser.set_status_error(error)
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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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return None
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def _handle_successful_response(browser: Browser, response: Response, url: str):
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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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Returns:
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The successfully handled URL on success, None otherwise.
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"""
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# Use appropriate response parser according to the MIME type.
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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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download_dir = browser.config["download_path"]
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filepath = _get_download_path(url, download_dir=download_dir)
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# If a page has been produced, load it. Else if a file has been retrieved,
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# download it.
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if page:
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browser.load_page(page)
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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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return 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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browser.last_download = mime_type, filepath
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return url
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elif error:
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browser.set_status_error(error)
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return None
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def _get_download_path(url: str, download_dir: Optional[str] =None) -> Path:
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"""Try to find the best download file path possible from this URL."""
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download_path = Path(download_dir) if download_dir else get_downloads_path()
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if not download_path.exists():
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download_path.mkdir(parents=True)
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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_path / filename
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def _handle_input_request(
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browser: Browser,
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from_url: str,
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message: str =None
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) -> Optional[str]:
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"""Focus command-line to pass input to the server.
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Returns:
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The result of `open_gemini_url` with the new request including user input.
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"""
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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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return open_gemini_url(browser, url)
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def _handle_cert_required(
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browser: Browser,
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response: Response,
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url: str,
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redirects: int
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) -> Optional[str]:
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"""Find a matching identity and resend the request with it.
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Returns:
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The result of `open_gemini_url` with the client certificate provided.
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"""
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identities = load_identities(get_identities_list_path())
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if not identities:
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browser.set_status_error(f"Can't load identities.")
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return None
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browser.identities = identities
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url_identities = get_identities_for_url(browser.identities, url)
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if not url_identities:
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identity = create_identity(browser, url)
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if not identity:
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return None
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browser.identities[url] = [identity]
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save_identities(browser.identities, get_identities_list_path())
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else:
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identity = select_identity(url_identities)
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cert_path, key_path = get_cert_and_key(identity["id"])
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return open_gemini_url(
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browser,
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url,
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redirects=redirects + 1,
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use_cache=False,
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cert_and_key=(cert_path, key_path)
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)
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def select_identity(identities: list):
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"""Let user select the appropriate identity among candidates."""
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# TODO support multiple identities; for now we just use the first available.
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return identities[0] if identities else None
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def create_identity(browser: Browser, url: str):
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"""Walk the user through identity creation.
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Returns:
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The created identity on success (already registered in identities
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"""
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key = browser.prompt("Create client certificate? [y/n]", "yn")
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if key != "y":
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browser.reset_status()
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return None
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common_name = browser.get_user_text_input(
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"Name? The server will see this, you can leave it empty.",
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CommandLine.CHAR_TEXT,
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strip=True,
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)
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if not common_name:
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browser.reset_status()
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return None
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browser.set_status("Generating certificate…")
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try:
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mangled_name = create_certificate(url, common_name)
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except ClientCertificateException as exc:
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browser.set_status_error(exc.message)
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return None
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browser.reset_status()
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return {"name": common_name, "id": mangled_name}
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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 for {hostname}? [y/n]", "yn")
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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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