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00cf68c6e8
curl/docs/KNOWN_BUGS
Daniel Stenberg 00cf68c6e8 KNOWN_BUGS: 1.8 DNS timing is wrong for HTTP redirects 
Closes #522
2016-04-08 13:03:37 +02:00

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Known Bugs
These are problems and bugs known to exist at the time of this release. Feel
free to join in and help us correct one or more of these! Also be sure to
check the changelog of the current development status, as one or more of these
problems may have been fixed or changed somewhat since this was written!
1. HTTP
1.1 CURLFORM_CONTENTLEN in an array
1.2 Disabling HTTP Pipelining
1.3 STARTTRANSFER time is wrong for HTTP POSTs
1.4 multipart formposts file name encoding
1.5 Expect-100 meets 417
1.6 Unnecessary close when 401 received waiting for 100
1.7 CONNECT response larger than 16KB
1.8 DNS timing is wrong for HTTP redirects
2. TLS
2.1 Hangs with PolarSSL
2.2 CURLINFO_SSL_VERIFYRESULT has limited support
2.3 DER in keychain
3. Email protocols
3.1 IMAP SEARCH ALL truncated response
3.2 No disconnect command
3.3 SMTP to multiple recipients
4. Command line
4.1 -J with %-encoded file nameas
4.2 -J with -C - fails
4.3 --retry and transfer timeouts
5. Build and portability issues
5.1 Windows Borland compiler
5.2 curl-config --libs contains private details
5.3 libidn and old iconv
5.4 AIX shared build with c-ares fails
5.5 can't handle Unicode arguments in Windows
6. Authentication
6.1 NTLM authentication and unicode
6.2 MIT Kerberos for Windows build
6.3 NTLM in system context uses wrong name
6.4 Negotiate needs a fake user name
7. FTP
7.1 FTP without or slow 220 response
7.2 FTP with CONNECT and slow server
7.3 FTP with NOBODY and FAILONERROR
7.4 FTP with ACCT
7.5 ASCII FTP
7.6 FTP with NULs in URL parts
7.7 FTP and empty path parts in the URL
8. TELNET
8.1 TELNET and time limtiations don't work
8.2 Microsoft telnet server
9. SFTP and SCP
9.1 SFTP doesn't do CURLOPT_POSTQUOTE correct
10. SOCKS
10.1 SOCKS proxy connections are done blocking
10.2 SOCKS don't support timeouts
10.3 FTPS over SOCKS
10.4 active FTP over a SOCKS
==============================================================================
1. HTTP
1.1 CURLFORM_CONTENTLEN in an array
It is not possible to pass a 64-bit value using CURLFORM_CONTENTLEN with
CURLFORM_ARRAY, when compiled on 32-bit platforms that support 64-bit
integers. This is because the underlying structure 'curl_forms' uses a dual
purpose char* for storing these values in via casting. For more information
see the now closed related issue:
https://github.com/curl/curl/issues/608
1.2 Disabling HTTP Pipelining
Disabling HTTP Pipelining when there are ongoing transfers can lead to
heap corruption and crash. https://curl.haxx.se/bug/view.cgi?id=1411
1.3 STARTTRANSFER time is wrong for HTTP POSTs
Wrong STARTTRANSFER timer accounting for POST requests Timer works fine with
GET requests, but while using POST the time for CURLINFO_STARTTRANSFER_TIME
is wrong. While using POST CURLINFO_STARTTRANSFER_TIME minus
CURLINFO_PRETRANSFER_TIME is near to zero every time.
https://github.com/curl/curl/issues/218
https://curl.haxx.se/bug/view.cgi?id=1213
1.4 multipart formposts file name encoding
When creating multipart formposts. The file name part can be encoded with
something beyond ascii but currently libcurl will only pass in the verbatim
string the app provides. There are several browsers that already do this
encoding. The key seems to be the updated draft to RFC2231:
https://tools.ietf.org/html/draft-reschke-rfc2231-in-http-02
1.5 Expect-100 meets 417
If an upload using Expect: 100-continue receives an HTTP 417 response, it
ought to be automatically resent without the Expect:. A workaround is for
the client application to redo the transfer after disabling Expect:.
https://curl.haxx.se/mail/archive-2008-02/0043.html
1.6 Unnecessary close when 401 received waiting for 100
libcurl closes the connection if an HTTP 401 reply is received while it is
waiting for the the 100-continue response.
https://curl.haxx.se/mail/lib-2008-08/0462.html
1.7 CONNECT response larger than 16KB
If a CONNECT response-headers are larger than BUFSIZE (16KB) when the
connection is meant to be kept alive (like for NTLM proxy auth), the function
will return prematurely and will confuse the rest of the HTTP protocol
code. This should be very rare.
1.8 DNS timing is wrong for HTTP redirects
When extracting timing information after HTTP redirects, only the last
transfer's results are returned and not the totals:
https://github.com/curl/curl/issues/522
2. TLS
2.1 Hangs with PolarSSL
"curl_easy_perform hangs with imap and PolarSSL"
https://github.com/curl/curl/issues/334
2.2 CURLINFO_SSL_VERIFYRESULT has limited support
CURLINFO_SSL_VERIFYRESULT is only implemented for the OpenSSL and NSS
backends, so relying on this information in a generic app is flaky.
2.3 DER in keychain
Curl doesn't recognize certificates in DER format in keychain, but it works
with PEM. https://curl.haxx.se/bug/view.cgi?id=1065
3. Email protocols
3.1 IMAP SEARCH ALL truncated response
IMAP "SEARCH ALL" truncates output on large boxes. "A quick search of the
code reveals that pingpong.c contains some truncation code, at line 408, when
it deems the server response to be too large truncating it to 40 characters"
https://curl.haxx.se/bug/view.cgi?id=1366
3.2 No disconnect command
The disconnect commands (LOGOUT and QUIT) may not be sent by IMAP, POP3 and
SMTP if a failure occurs during the authentication phase of a connection.
3.3 SMTP to multiple recipients
When sending data to multiple recipients, curl will abort and return failure
if one of the recipients indicate failure (on the "RCPT TO"
command). Ordinary mail programs would proceed and still send to the ones
that can receive data. This is subject for change in the future.
https://curl.haxx.se/bug/view.cgi?id=1116
4. Command line
4.1 -J with %-encoded file nameas
-J/--remote-header-name doesn't decode %-encoded file names. RFC6266 details
how it should be done. The can of worm is basically that we have no charset
handling in curl and ascii >=128 is a challenge for us. Not to mention that
decoding also means that we need to check for nastiness that is attempted,
like "../" sequences and the like. Probably everything to the left of any
embedded slashes should be cut off.
https://curl.haxx.se/bug/view.cgi?id=1294
4.2 -J with -C - fails
When using -J (with -O), automatically resumed downloading together with "-C
-" fails. Without -J the same command line works! This happens because the
resume logic is worked out before the target file name (and thus its
pre-transfer size) has been figured out!
https://curl.haxx.se/bug/view.cgi?id=1169
4.3 --retry and transfer timeouts
If using --retry and the transfer timeouts (possibly due to using -m or
-y/-Y) the next attempt doesn't resume the transfer properly from what was
downloaded in the previous attempt but will truncate and restart at the
original position where it was at before the previous failed attempt. See
https://curl.haxx.se/mail/lib-2008-01/0080.html and Mandriva bug report
https://qa.mandriva.com/show_bug.cgi?id=22565
5. Build and portability issues
5.1 Windows Borland compiler
When building with the Windows Borland compiler, it fails because the "tlib"
tool doesn't support hyphens (minus signs) in file names and we have such in
the build. https://curl.haxx.se/bug/view.cgi?id=1222
5.2 curl-config --libs contains private details
"curl-config --libs" will include details set in LDFLAGS when configure is
run that might be needed only for building libcurl. Further, curl-config
--cflags suffers from the same effects with CFLAGS/CPPFLAGS.
5.3 libidn and old iconv
Test case 165 might fail on a system which has libidn present, but with an
old iconv version (2.1.3 is a known bad version), since it doesn't recognize
the charset when named ISO8859-1. Changing the name to ISO-8859-1 makes the
test pass, but instead makes it fail on Solaris hosts that use its native
iconv.
5.4 AIX shared build with c-ares fails
curl version 7.12.2 fails on AIX if compiled with --enable-ares. The
workaround is to combine --enable-ares with --disable-shared
5.5 can't handle Unicode arguments in Windows
If a URL or filename can't be encoded using the user's current codepage then
it can only be encoded properly in the Unicode character set. Windows uses
UTF-16 encoding for Unicode and stores it in wide characters, however curl
and libcurl are not equipped for that at the moment. And, except for Cygwin,
Windows can't use UTF-8 as a locale.
https://curl.haxx.se/bug/?i=345
https://curl.haxx.se/bug/?i=731
6. Authentication
6.1 NTLM authentication and unicode
NTLM authentication involving unicode user name or password only works
properly if built with UNICODE defined together with the WinSSL/schannel
backend. The original problem was mentioned in:
https://curl.haxx.se/mail/lib-2009-10/0024.html
https://curl.haxx.se/bug/view.cgi?id=896
The WinSSL/schannel version verified to work as mentioned in
https://curl.haxx.se/mail/lib-2012-07/0073.html
6.2 MIT Kerberos for Windows build
libcurl fails to build with MIT Kerberos for Windows (KfW) due to KfW's
library header files exporting symbols/macros that should be kept private to
the KfW library. See ticket #5601 at http://krbdev.mit.edu/rt/
6.3 NTLM in system context uses wrong name
NTLM authentication using SSPI (on Windows) when (lib)curl is running in
"system context" will make it use wrong(?) user name - at least when compared
to what winhttp does. See https://curl.haxx.se/bug/view.cgi?id=535
6.4 Negotiate needs a fake user name
To get HTTP Negotiate (SPNEGO) authentication to work fine, you need to
provide a (fake) user name (this concerns both curl and the lib) because the
code wrongly only considers authentication if there's a user name provided.
https://curl.haxx.se/bug/view.cgi?id=440 How?
https://curl.haxx.se/mail/lib-2004-08/0182.html
7. FTP
7.1 FTP without or slow 220 response
If a connection is made to a FTP server but the server then just never sends
the 220 response or otherwise is dead slow, libcurl will not acknowledge the
connection timeout during that phase but only the "real" timeout - which may
surprise users as it is probably considered to be the connect phase to most
people. Brought up (and is being misunderstood) in:
https://curl.haxx.se/bug/view.cgi?id=856
7.2 FTP with CONNECT and slow server
When doing FTP over a socks proxy or CONNECT through HTTP proxy and the multi
interface is used, libcurl will fail if the (passive) TCP connection for the
data transfer isn't more or less instant as the code does not properly wait
for the connect to be confirmed. See test case 564 for a first shot at a test
case.
7.3 FTP with NOBODY and FAILONERROR
It seems sensible to be able to use CURLOPT_NOBODY and CURLOPT_FAILONERROR
with FTP to detect if a file exists or not, but it is not working:
https://curl.haxx.se/mail/lib-2008-07/0295.html
7.4 FTP with ACCT
When doing an operation over FTP that requires the ACCT command (but not when
logging in), the operation will fail since libcurl doesn't detect this and
thus fails to issue the correct command:
https://curl.haxx.se/bug/view.cgi?id=635
7.5 ASCII FTP
FTP ASCII transfers do not follow RFC959. They don't convert the data
accordingly (not for sending nor for receiving). RFC 959 section 3.1.1.1
clearly describes how this should be done:
The sender converts the data from an internal character representation to
the standard 8-bit NVT-ASCII representation (see the Telnet
specification). The receiver will convert the data from the standard
form to his own internal form.
Since 7.15.4 at least line endings are converted.
7.6 FTP with NULs in URL parts
FTP URLs passed to curl may contain NUL (0x00) in the RFC 1738 <user>,
<password>, and <fpath> components, encoded as "%00". The problem is that
curl_unescape does not detect this, but instead returns a shortened C string.
From a strict FTP protocol standpoint, NUL is a valid character within RFC
959 <string>, so the way to handle this correctly in curl would be to use a
data structure other than a plain C string, one that can handle embedded NUL
characters. From a practical standpoint, most FTP servers would not
meaningfully support NUL characters within RFC 959 <string>, anyway (e.g.,
Unix pathnames may not contain NUL).
7.7 FTP and empty path parts in the URL
libcurl ignores empty path parts in FTP URLs, whereas RFC1738 states that
such parts should be sent to the server as 'CWD ' (without an argument). The
only exception to this rule, is that we knowingly break this if the empty
part is first in the path, as then we use the double slashes to indicate that
the user wants to reach the root dir (this exception SHALL remain even when
this bug is fixed).
8. TELNET
8.1 TELNET and time limtiations don't work
When using telnet, the time limitation options don't work.
https://curl.haxx.se/bug/view.cgi?id=846
8.2 Microsoft telnet server
There seems to be a problem when connecting to the Microsoft telnet server.
https://curl.haxx.se/bug/view.cgi?id=649
9. SFTP and SCP
9.1 SFTP doesn't do CURLOPT_POSTQUOTE correct
When libcurl sends CURLOPT_POSTQUOTE commands when connected to a SFTP server
using the multi interface, the commands are not being sent correctly and
instead the connection is "cancelled" (the operation is considered done)
prematurely. There is a half-baked (busy-looping) patch provided in the bug
report but it cannot be accepted as-is. See
https://curl.haxx.se/bug/view.cgi?id=748
10. SOCKS
10.1 SOCKS proxy connections are done blocking
Both SOCKS5 and SOCKS4 proxy connections are done blocking, which is very bad
when used with the multi interface.
10.2 SOCKS don't support timeouts
The SOCKS4 connection codes don't properly acknowledge (connect) timeouts.
According to bug #1556528, even the SOCKS5 connect code does not do it right:
https://curl.haxx.se/bug/view.cgi?id=604
When connecting to a SOCK proxy, the (connect) timeout is not properly
acknowledged after the actual TCP connect (during the SOCKS "negotiate"
phase).
10.3 FTPS over SOCKS
libcurl doesn't support FTPS over a SOCKS proxy.
10.4 active FTP over a SOCKS
libcurl doesn't support active FTP over a SOCKS proxy
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