_ _ ____ _ ___| | | | _ \| | / __| | | | |_) | | | (__| |_| | _ <| |___ \___|\___/|_| \_\_____| 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 1.9 HTTP/2 frames while in the connection pool kill reuse 1.10 Strips trailing dot from host name 1.11 CURLOPT_SEEKFUNCTION not called with CURLFORM_STREAM 2. TLS 2.1 CURLINFO_SSL_VERIFYRESULT has limited support 2.2 DER in keychain 2.3 GnuTLS backend skips really long certificate fields 2.4 DarwinSSL won't import PKCS#12 client certificates without a password 2.5 Client cert handling with Issuer DN differs between backends 3. Email protocols 3.1 IMAP SEARCH ALL truncated response 3.2 No disconnect command 3.3 SMTP to multiple recipients 3.4 POP3 expects "CRLF.CRLF" eob for some single-line responses 4. Command line 4.1 -J and -O with %-encoded file names 4.2 -J with -C - fails 4.3 --retry and transfer timeouts 4.4 --upload-file . hang if delay in STDIN 5. Build and portability issues 5.1 Windows Borland compiler 5.2 curl-config --libs contains private details 5.4 AIX shared build with c-ares fails 5.5 can't handle Unicode arguments in Windows 5.6 cmake support gaps 5.7 Visual Studio project gaps 5.8 configure finding libs in wrong directory 5.9 Utilize Requires.private directives in libcurl.pc 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 and Kerberos V5 need 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 7.8 Premature transfer end but healthy control channel 7.9 Passive transfer tries only one IP address 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 11. Internals 11.1 Curl leaks .onion hostnames in DNS 11.2 error buffer not set if connection to multiple addresses fails 11.3 c-ares deviates from stock resolver on http://1346569778 11.4 HTTP test server 'connection-monitor' problems 11.5 Connection information when using TCP Fast Open 12. LDAP and OpenLDAP 12.1 OpenLDAP hangs after returning results 13. TCP/IP 13.1 --interface for ipv6 binds to unusable IP address 14 DICT 14.1 DICT responses show the underlying protocol ============================================================================== 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 1.9 HTTP/2 frames while in the connection pool kill reuse If the server sends HTTP/2 frames (like for example an HTTP/2 PING frame) to curl while the connection is held in curl's connection pool, the socket will be found readable when considered for reuse and that makes curl think it is dead and then it will be closed and a new connection gets created instead. This is *best* fixed by adding monitoring to connections while they are kept in the pool so that pings can be responded to appropriately. 1.10 Strips trailing dot from host name When given a URL with a trailing dot for the host name part: "https://example.com./", libcurl will strip off the dot and use the name without a dot internally and send it dot-less in HTTP Host: headers and in the TLS SNI field. The HTTP part violates RFC 7230 section 5.4 but the SNI part is accordance with RFC 6066 section 3. URLs using these trailing dots are very rare in the wild and we have not seen or gotten any real-world problems with such URLs reported. The popular browsers seem to have stayed with not stripping the dot for both uses (thus they violate RFC 6066 instead of RFC 7230). Daniel took the discussion to the HTTPbis mailing list in March 2016: https://lists.w3.org/Archives/Public/ietf-http-wg/2016JanMar/0430.html but there was not major rush or interest to fix this. The impression I get is that most HTTP people rather not rock the boat now and instead prioritize web compatibility rather than to strictly adhere to these RFCs. Our current approach allows a knowing client to send a custom HTTP header with the dot added. It can also be noted that while adding a trailing dot to the host name in most (all?) cases will make the name resolve to the same set of IP addresses, many HTTP servers will not happily accept the trailing dot there unless that has been specifically configured to be a fine virtual host. If URLs with trailing dots for host names become more popular or even just used more than for just plain fun experiments, I'm sure we will have reason to go back and reconsider. See https://github.com/curl/curl/issues/716 for the discussion. 1.11 CURLOPT_SEEKFUNCTION not called with CURLFORM_STREAM I'm using libcurl to POST form data using a FILE* with the CURLFORM_STREAM option of curl_formadd(). I've noticed that if the connection drops at just the right time, the POST is reattempted without the data from the file. It seems like the file stream position isn't getting reset to the beginning of the file. I found the CURLOPT_SEEKFUNCTION option and set that with a function that performs an fseek() on the FILE*. However, setting that didn't seem to fix the issue or even get called. See https://github.com/curl/curl/issues/768 2. TLS 2.1 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. 2.2 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 2.3 GnuTLS backend skips really long certificate fields libcurl calls gnutls_x509_crt_get_dn() with a fixed buffer size and if the field is too long in the cert, it'll just return an error and the field will be displayed blank. 2.4 DarwinSSL won't import PKCS#12 client certificates without a password libcurl calls SecPKCS12Import with the PKCS#12 client certificate, but that function rejects certificates that do not have a password. https://github.com/curl/curl/issues/1308 2.5 Client cert handling with Issuer DN differs between backends When the specified client certificate doesn't match any of the server-specified DNs, the OpenSSL and GnuTLS backends behave differently. The github discussion may contain a solution. See https://github.com/curl/curl/issues/1411 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 3.4 POP3 expects "CRLF.CRLF" eob for some single-line responses You have to tell libcurl not to expect a body, when dealing with one line response commands. Please see the POP3 examples and test cases which show this for the NOOP and DELE commands. https://curl.haxx.se/bug/?i=740 4. Command line 4.1 -J and -O with %-encoded file names -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 -O also doesn't decode %-encoded names, and while it has even less information about the charset involved the process is similar to the -J case. Note that we won't add decoding to -O without the user asking for it with some other means as well, since -O has always been documented to use the name exactly as specified in the URL. 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 4.4 --upload-file . hangs if delay in STDIN "(echo start; sleep 1; echo end) | curl --upload-file . http://mywebsite -vv" ... causes a hang when it shouldn't. See https://github.com/curl/curl/issues/2051 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. 5.4 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 5.6 cmake support gaps The cmake build setup lacks several features that the autoconf build offers. This includes: - use of correct soname for the shared library build - support for several TLS backends are missing - the unit tests cause link failures in regular non-static builds - no nghttp2 check 5.7 Visual Studio project gaps The Visual Studio projects lack some features that the autoconf and nmake builds offer, such as the following: - support for zlib and nghttp2 - use of static runtime libraries - add the test suite components In addition to this the following could be implemented: - support for other development IDEs - add PATH environment variables for third-party DLLs 5.8 configure finding libs in wrong directory When the configure script checks for third-party libraries, it adds those directories to the LDFLAGS variable and then tries linking to see if it works. When successful, the found directory is kept in the LDFLAGS variable when the script continues to execute and do more tests and possibly check for more libraries. This can make subsequent checks for libraries wrongly detect another installation in a directory that was previously added to LDFLAGS by another library check! A possibly better way to do these checks would be to keep the pristine LDFLAGS even after successful checks and instead add those verified paths to a separate variable that only after all library checks have been performed gets appended to LDFLAGS. 5.9 Utilize Requires.private directives in libcurl.pc https://github.com/curl/curl/issues/864 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 https://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 and Kerberos V5 need a fake user name In order to get Negotiate (SPNEGO) authentication to work in HTTP or Kerberos V5 in the e-mail protocols, 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 by setting conn->bits.user_passwd in url.c https://curl.haxx.se/bug/view.cgi?id=440 How? https://curl.haxx.se/mail/lib-2004-08/0182.html A possible solution is to either modify this variable to be set or introduce a variable such as new conn->bits.want_authentication which is set when any of the authentication options are set. 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 , , and 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 , 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 , 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). 7.8 Premature transfer end but healthy control channel When 'multi_done' is called before the transfer has been completed the normal way, it is considered a "premature" transfer end. In this situation, libcurl closes the connection assuming it doesn't know the state of the connection so it can't be reused for subsequent requests. With FTP however, this isn't necessarily true but there are a bunch of situations (listed in the ftp_done code) where it *could* keep the connection alive even in this situation - but the current code doesn't. Fixing this would allow libcurl to reuse FTP connections better. 7.9 Passive transfer tries only one IP address When doing FTP operations through a proxy at localhost, the reported spotted that curl only tried to connect once to the proxy, while it had mulitiple addresses and a failed connect on one address should make it try the next. After switching to passive mode (EPSV), curl should try all IP addresses for "localhost". Currently it tries ::1, but it should also try 127.0.0.1. See https://github.com/curl/curl/issues/1508 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 11. Internals 11.1 Curl leaks .onion hostnames in DNS Curl sends DNS requests for hostnames with a .onion TLD. This leaks information about what the user is attempting to access, and violates this requirement of RFC7686: https://tools.ietf.org/html/rfc7686 Issue: https://github.com/curl/curl/issues/543 11.2 error buffer not set if connection to multiple addresses fails If you ask libcurl to resolve a hostname like example.com to IPv6 addresses only. But you only have IPv4 connectivity. libcurl will correctly fail with CURLE_COULDNT_CONNECT. But the error buffer set by CURLOPT_ERRORBUFFER remains empty. Issue: https://github.com/curl/curl/issues/544 11.3 c-ares deviates from stock resolver on http://1346569778 When using the socket resolvers, that URL becomes: * Rebuilt URL to: http://1346569778/ * Trying 80.67.6.50... but with c-ares it instead says "Could not resolve: 1346569778 (Domain name not found)" See https://github.com/curl/curl/issues/893 11.4 HTTP test server 'connection-monitor' problems The 'connection-monitor' feature of the sws HTTP test server doesn't work properly if some tests are run in unexpected order. Like 1509 and then 1525. See https://github.com/curl/curl/issues/868 11.5 Connection information when using TCP Fast Open CURLINFO_LOCAL_PORT (and possibly a few other) fails when TCP Fast Open is enabled. See https://github.com/curl/curl/issues/1332 12. LDAP and OpenLDAP 12.1 OpenLDAP hangs after returning results By configuration defaults, openldap automatically chase referrals on secondary socket descriptors. The OpenLDAP backend is asynchronous and thus should monitor all socket descriptors involved. Currently, these secondary descriptors are not monitored, causing openldap library to never receive data from them. As a temporary workaround, disable referrals chasing by configuration. The fix is not easy: proper automatic referrals chasing requires a synchronous bind callback and monitoring an arbitrary number of socket descriptors for a single easy handle (currently limited to 5). Generic LDAP is synchronous: OK. See https://github.com/curl/curl/issues/622 and https://curl.haxx.se/mail/lib-2016-01/0101.html 13. TCP/IP 13.1 --interface for ipv6 binds to unusable IP address Since IPv6 provides a lot of addresses with different scope, binding to an IPv6 address needs to take the proper care so that it doesn't bind to a locally scoped address as that is bound to fail. https://github.com/curl/curl/issues/686 14. DICT 14.1 DICT responses show the underlying protocol When getting a DICT response, the protocol parts of DICT aren't stripped off from the output. https://github.com/curl/curl/issues/1809