Bug? http.client assumes iso-8859-1 encoding of HTTP headers
Hi Python devs, I am trying to download an HTML document. I get an HTTP 301 (Moved Permanently) with a UTF-8 encoded Location header and http.client decodes it as iso-8859-1. When there's a non-ASCII character in the redirect URL then I can't download the document. In client.py def parse_headers() I see the call to decode('iso-8859-1'). My personal hack is to use whatever charset is defined in the Content-Type HTTP header (utf8) or fall back into iso-8859-1. At this point I am not sure where/how a fix should occur so I thought I'd run it by you in case I should file a bug. Note that I don't use http.client directly, but through the python-requests library. I include some code to reproduce the problem below. Cheers, Hugo ----- #!/usr/bin/env python3 # Trying to replicate what wget does with a 301 redirect: # wget --server-response www.starbucks.com/store/158/AT/Karntnerstrasse/K%c3%a4rntnerstrasse-49-Vienna-9-1010 import http.client import urllib.parse s2='/store/158/AT/Karntnerstrasse/K%c3%a4rntnerstrasse-49-Vienna-9-1010' s3=' http://www.starbucks.com/store/158/at/karntnerstrasse/k%C3%A4rntnerstrasse-4... ' conn = http.client.HTTPConnection('www.starbucks.com') conn.request('GET', s2) r = conn.getresponse() print('Location', r.headers.get('Location')) print('Expected', urllib.parse.unquote(s3)) assert r.status == 301 assert r.headers.get('Location') == urllib.parse.unquote(s3), \ 'decoded as iso-8859-1 instead of utf8' conn = http.client.HTTPConnection('www.starbucks.com') conn.request('GET', s3) r = conn.getresponse() assert r.status == 200
On Sun, Jan 5, 2014 at 2:36 AM, Hugo G. Fierro <hugo@gfierro.com> wrote:
I am trying to download an HTML document. I get an HTTP 301 (Moved Permanently) with a UTF-8 encoded Location header and http.client decodes it as iso-8859-1. When there's a non-ASCII character in the redirect URL then I can't download the document.
In client.py def parse_headers() I see the call to decode('iso-8859-1'). My personal hack is to use whatever charset is defined in the Content-Type HTTP header (utf8) or fall back into iso-8859-1.
At this point I am not sure where/how a fix should occur so I thought I'd run it by you in case I should file a bug. Note that I don't use http.client directly, but through the python-requests library.
I'm not 100% sure, but I believe non-ASCII characters are outright forbidden in a Location: header. It's possible that an RFC2047 tag might be used, but my reading of RFC2616 is that that's only for text fields, not for Location. These non-ASCII characters ought to be percent-encoded, and anything doing otherwise is buggy. Confirming what you're seeing with a plain socket:
s=socket.socket() s.connect(("www.starbucks.com",80)) s.send(b'GET /store/158/AT/Karntnerstrasse/K%c3%a4rntnerstrasse-49-Vienna-9-1010 HTTP/1.1\r\nHost: www.starbucks.com\r\nAccept-Encoding: identity\r\n\r\n') 136 s.recv(1024) b'HTTP/1.1 301 Moved Permanently\r\nContent-Type: text/html; charset=UTF-8\r\nLocation: http://www.starbucks.com/store/158/at/karntnerstrasse/k\xc3\xa4rntnerstrasse-49-vienna-9-1010\r\n ........'
I'm pretty sure that server is in violation of the spec, so all bets are off as to what any other server will do. If you know you're dealing with this one server, you can probably hack around this, but I don't think it belongs in core code. Unless, of course, I'm completely wrong about the spec, or if there's a de facto spec that lots of servers follow, in which case maybe it would be worth doing. ChrisA
On 2014-01-04, at 17:24 , Chris Angelico <rosuav@gmail.com> wrote:
On Sun, Jan 5, 2014 at 2:36 AM, Hugo G. Fierro <hugo@gfierro.com> wrote:
I am trying to download an HTML document. I get an HTTP 301 (Moved Permanently) with a UTF-8 encoded Location header and http.client decodes it as iso-8859-1. When there's a non-ASCII character in the redirect URL then I can't download the document.
In client.py def parse_headers() I see the call to decode('iso-8859-1'). My personal hack is to use whatever charset is defined in the Content-Type HTTP header (utf8) or fall back into iso-8859-1.
At this point I am not sure where/how a fix should occur so I thought I'd run it by you in case I should file a bug. Note that I don't use http.client directly, but through the python-requests library.
I'm not 100% sure, but I believe non-ASCII characters are outright forbidden in a Location: header. It's possible that an RFC2047 tag might be used, but my reading of RFC2616 is that that's only for text fields, not for Location. These non-ASCII characters ought to be percent-encoded, and anything doing otherwise is buggy.
That is also my reading, the Location field’s value is defined as an absoluteURI (RFC2616, section 14.30):
Location = "Location" ":" absoluteURI
section 3.2.1 indicates that "absoluteURI" (and other related concepts) are used as defined by RFC 2396 "Uniform Resource Identifiers (URI): Generic Syntax", that is:
absoluteURI = scheme ":" ( hier_part | opaque_part )
both "hier_part" and "opaque_part" consist of some punctuation characters, "escaped" and "unreserved". "escaped" is %-encoded characters which leaves "unreserved" defined as "alphanum | mark". "mark" is more punctuation and "alphanum" is ASCII's alphanumeric ranges. Furthermore, although RFC 3986 moves some stuff around and renames some production rules, it seems to have kept this limitation.
Quoting Chris Angelico <rosuav@gmail.com>:
I'm pretty sure that server is in violation of the spec, so all bets are off as to what any other server will do. If you know you're dealing with this one server, you can probably hack around this, but I don't think it belongs in core code. Unless, of course, I'm completely wrong about the spec, or if there's a de facto spec that lots of servers follow, in which case maybe it would be worth doing.
It would be possible to support this better by using "ascii" with "surrogateescape" when receiving the redirect, and using the same for all URLs coming into http.client. This would implement a best-effort strategy at preserving the bogus URL, and still maintain the notion that URLs are text (with the other path being to also allow bytes as URLs, and always parsing Location as bytes). Regards, Martin
participants (4)
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Chris Angelico -
Hugo G. Fierro -
martin＠v.loewis.de -
Xavier Morel