TODO -- nice to have features

libcurl

1.2 More data sharing
1.3 struct lifreq
1.4 signal-based resolver timeouts
1.5 get rid of PATH_MAX
1.6 Modified buffer size approach
1.7 Detect when called from within callbacks
1.9 Cache negative name resolves
1.11 minimize dependencies with dynamicly loaded modules
1.12 have form functions use CURL handle argument
1.14 Typesafe curl_easy_setopt()
1.15 Monitor connections in the connection pool
1.16 Try to URL encode given URL
1.17 Add support for IRIs
1.18 try next proxy if one doesn't work
1.19 Timeout idle connections from the pool
1.20 SRV and URI DNS records
1.21 API for URL parsing/splitting
1.23 Offer API to flush the connection pool
1.24 TCP Fast Open for windows
1.25 Remove the generated include file

libcurl - multi interface

2.1 More non-blocking
2.2 Better support for same name resolves
2.3 Non-blocking curl_multi_remove_handle()
2.4 Split connect and authentication process
2.5 Edge-triggered sockets should work

Documentation

3.1 Update date and version in man pages
3.2 Provide cmake config-file

FTP

4.1 HOST
4.2 Alter passive/active on failure and retry
4.3 Earlier bad letter detection
4.4 REST for large files
4.5 ASCII support
4.6 GSSAPI via Windows SSPI
4.7 STAT for LIST without data connection

HTTP

5.1 Better persistency for HTTP 1.0
5.2 support FF3 sqlite cookie files
5.3 Rearrange request header order
5.5 auth= in URLs
5.6 Refuse "downgrade" redirects
5.7 Brotli compression
5.8 QUIC
5.9 Add easy argument to formpost functions
5.10 Leave secure cookies alone

TELNET

6.1 ditch stdin
6.2 ditch telnet-specific select
6.3 feature negotiation debug data
6.4 send data in chunks

SMTP

7.1 Pipelining
7.2 Enhanced capability support
7.3 Add CURLOPT_MAIL_CLIENT option

POP3

8.1 Pipelining
8.2 Enhanced capability support

IMAP

9.1 Enhanced capability support

LDAP

10.1 SASL based authentication mechanisms

SMB

11.1 File listing support
11.2 Honor file timestamps
11.3 Use NTLMv2
11.4 Create remote directories

New protocols

12.1 RSYNC

SSL

13.1 Disable specific versions
13.2 Provide mutex locking API
13.3 Evaluate SSL patches
13.4 Cache OpenSSL contexts
13.5 Export session ids
13.6 Provide callback for cert verification
13.7 improve configure --with-ssl
13.8 Support DANE
13.9 Support TLS v1.3
13.10 Support SSLKEYLOGFILE
13.11 Support intermediate & root pinning for PINNEDPUBLICKEY
13.12 Support HSTS
13.13 Support HPKP

GnuTLS

14.1 SSL engine stuff
14.2 check connection

WinSSL/SChannel

15.1 Add support for client certificate authentication
15.2 Add support for custom server certificate validation
15.3 Add support for the --ciphers option

SASL

16.1 Other authentication mechanisms
16.2 Add QOP support to GSSAPI authentication
16.3 Support binary messages (i.e.: non-base64)

SSH protocols

17.1 Multiplexing
17.2 SFTP performance
17.3 Support better than MD5 hostkey hash

Command line tool

18.1 sync
18.2 glob posts
18.3 prevent file overwriting
18.4 simultaneous parallel transfers
18.5 provide formpost headers
18.6 warning when setting an option
18.7 warning when sending binary output to terminal
18.8 offer color-coded HTTP header output
18.9 Choose the name of file in braces for complex URLs
18.10 improve how curl works in a windows console window
18.11 -w output to stderr
18.12 keep running, read instructions from pipe/socket
18.13 support metalink in http headers
18.14 --fail without --location should treat 3xx as a failure
18.15 Introduce --fail-fast to exit on first transfer fail
18.16 --retry should resume

Build

19.1 roffit
19.2 Enable PIE and RELRO by default

Test suite

20.1 SSL tunnel
20.2 nicer lacking perl message
20.3 more protocols supported
20.4 more platforms supported
20.5 Add support for concurrent connections
20.6 Use the RFC6265 test suite

Next SONAME bump

21.1 http-style HEAD output for FTP
21.2 combine error codes
21.3 extend CURLOPT_SOCKOPTFUNCTION prototype

Next major release

22.1 cleanup return codes
22.2 remove obsolete defines
22.3 size_t
22.4 remove several functions
22.5 remove CURLOPT_FAILONERROR
22.6 remove CURLOPT_DNS_USE_GLOBAL_CACHE
22.7 remove progress meter from libcurl
22.8 remove 'curl_httppost' from public


1. libcurl

1.2 More data sharing

curl_share_* functions already exist and work, and they can be extended to share more. For example, enable sharing of the ares channel and the connection cache.

1.3 struct lifreq

Use 'struct lifreq' and SIOCGLIFADDR instead of 'struct ifreq' and SIOCGIFADDR on newer Solaris versions as they claim the latter is obsolete. To support IPv6 interface addresses for network interfaces properly.

1.4 signal-based resolver timeouts

libcurl built without an asynchronous resolver library uses alarm() to time out DNS lookups. When a timeout occurs, this causes libcurl to jump from the signal handler back into the library with a sigsetjmp, which effectively causes libcurl to continue running within the signal handler. This is non-portable and could cause problems on some platforms. A discussion on the problem is available at https://curl.haxx.se/mail/lib-2008-09/0197.html

Also, alarm() provides timeout resolution only to the nearest second. alarm ought to be replaced by setitimer on systems that support it.

1.5 get rid of PATH_MAX

Having code use and rely on PATH_MAX is not nice: http://insanecoding.blogspot.com/2007/11/pathmax-simply-isnt.html

Currently the SSH based code uses it a bit, but to remove PATH_MAX from there we need libssh2 to properly tell us when we pass in a too small buffer and its current API (as of libssh2 1.2.7) doesn't.

1.6 Modified buffer size approach

Current libcurl allocates a fixed 16K size buffer for download and an additional 16K for upload. They are always unconditionally part of the easy handle. If CRLF translations are requested, an additional 32K "scratch buffer" is allocated. A total of 64K transfer buffers in the worst case.

First, while the handles are not actually in use these buffers could be freed so that lingering handles just kept in queues or whatever waste less memory.

Secondly, SFTP is a protocol that needs to handle many ~30K blocks at once since each need to be individually acked and therefore libssh2 must be allowed to send (or receive) many separate ones in parallel to achieve high transfer speeds. A current libcurl build with a 16K buffer makes that impossible, but one with a 512K buffer will reach MUCH faster transfers. But allocating 512K unconditionally for all buffers just in case they would like to do fast SFTP transfers at some point is not a good solution either.

Dynamically allocate buffer size depending on protocol in use in combination with freeing it after each individual transfer? Other suggestions?

1.7 Detect when called from within callbacks

We should set a state variable before calling callbacks, so that we subsequently can add code within libcurl that returns error if called within callbacks for when that's not supported.

1.9 Cache negative name resolves

A name resolve that has failed is likely to fail when made again within a short period of time. Currently we only cache positive responses.

1.11 minimize dependencies with dynamicly loaded modules

We can create a system with loadable modules/plug-ins, where these modules would be the ones that link to 3rd party libs. That would allow us to avoid having to load ALL dependencies since only the necessary ones for this app/invoke/used protocols would be necessary to load. See https://github.com/curl/curl/issues/349

1.12 have form functions use CURL handle argument

curl_formadd() and curl_formget() both currently have no CURL handle argument, but both can use a callback that is set in the easy handle, and thus curl_formget() with callback cannot function without first having curl_easy_perform() (or similar) called - which is hard to grasp and a design mistake.

The curl_formadd() design can probably also be reconsidered to make it easier to use and less error-prone. Probably easiest by splitting it into several function calls.

1.14 Typesafe curl_easy_setopt()

One of the most common problems in libcurl using applications is the lack of type checks for curl_easy_setopt() which happens because it accepts varargs and thus can take any type.

One possible solution to this is to introduce a few different versions of the setopt version for the different kinds of data you can set.

curl_easy_set_num() - sets a long value

curl_easy_set_large() - sets a curl_off_t value

curl_easy_set_ptr() - sets a pointer

curl_easy_set_cb() - sets a callback PLUS its callback data

1.15 Monitor connections in the connection pool

libcurl's connection cache or pool holds a number of open connections for the purpose of possible subsequent connection reuse. It may contain a few up to a significant amount of connections. Currently, libcurl leaves all connections as they are and first when a connection is iterated over for matching or reuse purpose it is verified that it is still alive.

Those connections may get closed by the server side for idleness or they may get a HTTP/2 ping from the peer to verify that they're still alive. By adding monitoring of the connections while in the pool, libcurl can detect dead connections (and close them) better and earlier, and it can handle HTTP/2 pings to keep such ones alive even when not actively doing transfers on them.

1.16 Try to URL encode given URL

Given a URL that for example contains spaces, libcurl could have an option that would try somewhat harder than it does now and convert spaces to %20 and perhaps URL encoded byte values over 128 etc (basically do what the redirect following code already does).

https://github.com/curl/curl/issues/514

1.17 Add support for IRIs

IRIs (RFC 3987) allow localized, non-ascii, names in the URL. To properly support this, curl/libcurl would need to translate/encode the given input from the input string encoding into percent encoded output "over the wire".

To make that work smoothly for curl users even on Windows, curl would probably need to be able to convert from several input encodings.

1.18 try next proxy if one doesn't work

Allow an application to specify a list of proxies to try, and failing to connect to the first go on and try the next instead until the list is exhausted. Browsers support this feature at least when they specify proxies using PACs.

https://github.com/curl/curl/issues/896

1.19 Timeout idle connections from the pool

libcurl currently keeps connections in its connection pool for an indefinite period of time, until it either gets reused, gets noticed that it has been closed by the server or gets pruned to make room for a new connection.

To reduce overhead (especially for when we add monitoring of the connections in the pool), we should introduce a timeout so that connections that have been idle for N seconds get closed.

1.20 SRV and URI DNS records

Offer support for resolving SRV and URI DNS records for libcurl to know which server to connect to for various protocols (including HTTP!).

1.21 API for URL parsing/splitting

libcurl has always parsed URLs internally and never exposed any API or features to allow applications to do it. Still most or many applications using libcurl need that ability. In polls to users, we've learned that many libcurl users would like to see and use such an API.

1.23 Offer API to flush the connection pool

Sometimes applications want to flush all the existing connections kept alive. An API could allow a forced flush or just a forced loop that would properly close all connections that have been closed by the server already.

1.24 TCP Fast Open for windows

libcurl supports the CURLOPT_TCP_FASTOPEN option since 7.49.0 for Linux and Mac OS. Windows supports TCP Fast Open starting with Windows 10, version 1607 and we should add support for it.

1.25 Remove the generated include file

When curl and libcurl are built, one of the public include files are generated and is populated with a set of defines that are derevid from sizes and constants for the particular target architecture that build is made. For platforms that can select between 32 bit and 64 bit at build time, this approach makes the libcurl build only create a set of public headers suitable for one of the architectures and not both. If you build libcurl for such a platform and you want to allow applications to get built using either 32/64 version, you must generate the libcurl headers once for each setup and you must then add a replacement curl header that would itself select the correct 32 or 64 bit specific header as necessary.

Your curl/curl.h alternative could then look like (replace with suitable CPP variable to check):

 #ifdef ARCH_32bit
 #include <curl32/curl.h>
 #else /* ARCH_64bit */
 #include <curl64/curl.h>
 #endif

A fix would either (A) fix the 32/64 setup automatically or even better (B) work away the architecture specific defines from the headers so that they can be used for all architectures independently of what libcurl was built for.

2. libcurl - multi interface

2.1 More non-blocking

Make sure we don't ever loop because of non-blocking sockets returning EWOULDBLOCK or similar. Blocking cases include:

- Name resolves on non-windows unless c-ares is used - NSS SSL connections - HTTP proxy CONNECT operations - SOCKS proxy handshakes - file:// transfers - TELNET transfers - The "DONE" operation (post transfer protocol-specific actions) for the

protocols SFTP, SMTP, FTP. Fixing Curl_done() for this is a worthy task.

2.2 Better support for same name resolves

If a name resolve has been initiated for name NN and a second easy handle wants to resolve that name as well, make it wait for the first resolve to end up in the cache instead of doing a second separate resolve. This is especially needed when adding many simultaneous handles using the same host name when the DNS resolver can get flooded.

2.3 Non-blocking curl_multi_remove_handle()

The multi interface has a few API calls that assume a blocking behavior, like add_handle() and remove_handle() which limits what we can do internally. The multi API need to be moved even more into a single function that "drives" everything in a non-blocking manner and signals when something is done. A remove or add would then only ask for the action to get started and then multi_perform() etc still be called until the add/remove is completed.

2.4 Split connect and authentication process

The multi interface treats the authentication process as part of the connect phase. As such any failures during authentication won't trigger the relevant QUIT or LOGOFF for protocols such as IMAP, POP3 and SMTP.

2.5 Edge-triggered sockets should work

The multi_socket API should work with edge-triggered socket events. One of the internal actions that need to be improved for this to work perfectly is the 'maxloops' handling in transfer.c:readwrite_data().

3. Documentation

3.1 Update date and version in man pages

'maketgz' or another suitable script could update the .TH sections of the man pages at release time to use the current date and curl/libcurl version number.

3.2 Provide cmake config-file

A config-file package is a set of files provided by us to allow applications to write cmake scripts to find and use libcurl easier. See https://github.com/curl/curl/issues/885

4. FTP

4.1 HOST

HOST is a command for a client to tell which host name to use, to offer FTP servers named-based virtual hosting:

https://tools.ietf.org/html/rfc7151

4.2 Alter passive/active on failure and retry

When trying to connect passively to a server which only supports active connections, libcurl returns CURLE_FTP_WEIRD_PASV_REPLY and closes the connection. There could be a way to fallback to an active connection (and vice versa). https://curl.haxx.se/bug/feature.cgi?id=1754793

4.3 Earlier bad letter detection

Make the detection of (bad) %0d and %0a codes in FTP URL parts earlier in the process to avoid doing a resolve and connect in vain.

4.4 REST for large files

REST fix for servers not behaving well on >2GB requests. This should fail if the server doesn't set the pointer to the requested index. The tricky (impossible?) part is to figure out if the server did the right thing or not.

4.5 ASCII support

FTP ASCII transfers do not follow RFC959. They don't convert the data accordingly.

4.6 GSSAPI via Windows SSPI

In addition to currently supporting the SASL GSSAPI mechanism (Kerberos V5) via third-party GSS-API libraries, such as Heimdal or MIT Kerberos, also add support for GSSAPI authentication via Windows SSPI.

4.7 STAT for LIST without data connection

Some FTP servers allow STAT for listing directories instead of using LIST, and the response is then sent over the control connection instead of as the otherwise usedw data connection: http://www.nsftools.com/tips/RawFTP.htm#STAT This is not detailed in any FTP specification.

5. HTTP

5.1 Better persistency for HTTP 1.0

"Better" support for persistent connections over HTTP 1.0 https://curl.haxx.se/bug/feature.cgi?id=1089001

5.2 support FF3 sqlite cookie files

Firefox 3 is changing from its former format to a a sqlite database instead. We should consider how (lib)curl can/should support this. https://curl.haxx.se/bug/feature.cgi?id=1871388

5.3 Rearrange request header order

Server implementors often make an effort to detect browser and to reject clients it can detect to not match. One of the last details we cannot yet control in libcurl's HTTP requests, which also can be exploited to detect that libcurl is in fact used even when it tries to impersonate a browser, is the order of the request headers. I propose that we introduce a new option in which you give headers a value, and then when the HTTP request is built it sorts the headers based on that number. We could then have internally created headers use a default value so only headers that need to be moved have to be specified.

5.5 auth= in URLs

Add the ability to specify the preferred authentication mechanism to use by using ;auth=<mech> in the login part of the URL.

For example:

http://test:pass;auth=NTLM@example.com would be equivalent to specifying --user test:pass;auth=NTLM or --user test:pass --ntlm from the command line.

Additionally this should be implemented for proxy base URLs as well.

5.6 Refuse "downgrade" redirects

See https://github.com/curl/curl/issues/226

Consider a way to tell curl to refuse to "downgrade" protocol with a redirect and/or possibly a bit that refuses redirect to change protocol completely.

5.7 Brotli compression

Compression algorithms that perform better than gzip are being considered for use and inclusion in existing browsers. For example 'brotli'. If servers follow along it is a good reason for us to also allow users to take advantage of this. The algorithm: https://github.com/google/brotli The Firefox bug: https://bugzilla.mozilla.org/show_bug.cgi?id=366559

5.8 QUIC

The standardization process of QUIC has been taken to the IETF and can be followed on the [IETF QUIC Mailing list](https://www.ietf.org/mailman/listinfo/quic). I'd like us to get on the bandwagon. Ideally, this would be done with a separate library/project to handle the binary/framing layer in a similar fashion to how HTTP/2 is implemented. This, to allow other projects to benefit from the work and to thus broaden the interest and chance of others to participate.

5.9 Add easy argument to formpost functions

Make sure there's an easy handle passed in to `curl_formadd()`, `curl_formget()` and `curl_formfree()` by adding replacement functions and deprecating the old ones. Allows better error messages and is generally good API hygiene.

5.10 Leave secure cookies alone

Non-secure origins (HTTP sites) should not be allowed to set or modify cookies with the 'secure' property:

https://tools.ietf.org/html/draft-ietf-httpbis-cookie-alone-01

6. TELNET

6.1 ditch stdin

Reading input (to send to the remote server) on stdin is a crappy solution for library purposes. We need to invent a good way for the application to be able to provide the data to send.

6.2 ditch telnet-specific select

Move the telnet support's network select() loop go away and merge the code into the main transfer loop. Until this is done, the multi interface won't work for telnet.

6.3 feature negotiation debug data

Add telnet feature negotiation data to the debug callback as header data.

6.4 send data in chunks

Currently, telnet sends data one byte at a time. This is fine for interactive use, but inefficient for any other. Sent data should be sent in larger chunks.

7. SMTP

7.1 Pipelining

Add support for pipelining emails.

7.2 Enhanced capability support

Add the ability, for an application that uses libcurl, to obtain the list of capabilities returned from the EHLO command.

7.3 Add CURLOPT_MAIL_CLIENT option

Rather than use the URL to specify the mail client string to present in the HELO and EHLO commands, libcurl should support a new CURLOPT specifically for specifying this data as the URL is non-standard and to be honest a bit of a hack ;-)

Please see the following thread for more information: https://curl.haxx.se/mail/lib-2012-05/0178.html

8. POP3

8.1 Pipelining

Add support for pipelining commands.

8.2 Enhanced capability support

Add the ability, for an application that uses libcurl, to obtain the list of capabilities returned from the CAPA command.

9. IMAP

9.1 Enhanced capability support

Add the ability, for an application that uses libcurl, to obtain the list of capabilities returned from the CAPABILITY command.

10. LDAP

10.1 SASL based authentication mechanisms

Currently the LDAP module only supports ldap_simple_bind_s() in order to bind to an LDAP server. However, this function sends username and password details using the simple authentication mechanism (as clear text). However, it should be possible to use ldap_bind_s() instead specifying the security context information ourselves.

11. SMB

11.1 File listing support

Add support for listing the contents of a SMB share. The output should probably be the same as/similar to FTP.

11.2 Honor file timestamps

The timestamp of the transferred file should reflect that of the original file.

11.3 Use NTLMv2

Currently the SMB authentication uses NTLMv1.

11.4 Create remote directories

Support for creating remote directories when uploading a file to a directory that doesn't exist on the server, just like --ftp-create-dirs.

12. New protocols

12.1 RSYNC

There's no RFC for the protocol or an URI/URL format. An implementation should most probably use an existing rsync library, such as librsync.

13. SSL

13.1 Disable specific versions

Provide an option that allows for disabling specific SSL versions, such as SSLv2 https://curl.haxx.se/bug/feature.cgi?id=1767276

13.2 Provide mutex locking API

Provide a libcurl API for setting mutex callbacks in the underlying SSL library, so that the same application code can use mutex-locking independently of OpenSSL or GnutTLS being used.

13.3 Evaluate SSL patches

Evaluate/apply Gertjan van Wingerde's SSL patches: https://curl.haxx.se/mail/lib-2004-03/0087.html

13.4 Cache OpenSSL contexts

"Look at SSL cafile - quick traces look to me like these are done on every request as well, when they should only be necessary once per SSL context (or once per handle)". The major improvement we can rather easily do is to make sure we don't create and kill a new SSL "context" for every request, but instead make one for every connection and re-use that SSL context in the same style connections are re-used. It will make us use slightly more memory but it will libcurl do less creations and deletions of SSL contexts.

13.5 Export session ids

Add an interface to libcurl that enables "session IDs" to get exported/imported. Cris Bailiff said: "OpenSSL has functions which can serialise the current SSL state to a buffer of your choice, and recover/reset the state from such a buffer at a later date - this is used by mod_ssl for apache to implement and SSL session ID cache".

13.6 Provide callback for cert verification

OpenSSL supports a callback for customised verification of the peer certificate, but this doesn't seem to be exposed in the libcurl APIs. Could it be? There's so much that could be done if it were!

13.7 improve configure --with-ssl

make the configure --with-ssl option first check for OpenSSL, then GnuTLS, then NSS...

13.8 Support DANE

DNS-Based Authentication of Named Entities (DANE) is a way to provide SSL keys and certs over DNS using DNSSEC as an alternative to the CA model. https://www.rfc-editor.org/rfc/rfc6698.txt

An initial patch was posted by Suresh Krishnaswamy on March 7th 2013 (https://curl.haxx.se/mail/lib-2013-03/0075.html) but it was a too simple approach. See Daniel's comments: https://curl.haxx.se/mail/lib-2013-03/0103.html . libunbound may be the correct library to base this development on.

Björn Stenberg wrote a separate initial take on DANE that was never completed.

13.9 Support TLS v1.3

TLS version 1.3 is about to ship and is getting implemented by TLS libraries as we speak. We should start to support the symbol and make sure all backends handle it accordingly, then gradually add support as the TLS libraries add the corresponding support. There may be a need to add some additional options to allow libcurl to take advantage of the new features in 1.3.

13.10 Support SSLKEYLOGFILE

When used, Firefox and Chrome dumps their master TLS keys to the file name this environment variable specifies. This allows tools like for example Wireshark to capture and decipher TLS traffic to/from those clients. libcurl could be made to support this more widely (presumably this already works when built with NSS). Peter Wu made a OpenSSL preload to make possible that can be used as inspiration and guidance https://git.lekensteyn.nl/peter/wireshark-notes/tree/src/sslkeylog.c

13.11 Support intermediate & root pinning for PINNEDPUBLICKEY

CURLOPT_PINNEDPUBLICKEY does not consider the hashes of intermediate & root certificates when comparing the pinned keys. Therefore it is not compatible with "HTTP Public Key Pinning" as there also intermediate and root certificates can be pinned. This is very useful as it prevents webadmins from "locking themself out of their servers".

Adding this feature would make curls pinning 100% compatible to HPKP and allow more flexible pinning.

13.12 Support HSTS

"HTTP Strict Transport Security" is TOFU (trust on first use), time-based features indicated by a HTTP header send by the webserver. It is widely used in browsers and it's purpose is to prevent insecure HTTP connections after a previous HTTPS connection. It protects against SSLStripping attacks.

Doc: https://developer.mozilla.org/en-US/docs/Web/Security/HTTP_strict_transport_security RFC 6797: https://tools.ietf.org/html/rfc6797

13.13 Support HPKP

"HTTP Public Key Pinning" is TOFU (trust on first use), time-based features indicated by a HTTP header send by the webserver. It's purpose is to prevent Man-in-the-middle attacks by trusted CAs by allowing webadmins to specify which CAs/certificates/public keys to trust when connection to their websites.

It can be build based on PINNEDPUBLICKEY.

Wikipedia: https://en.wikipedia.org/wiki/HTTP_Public_Key_Pinning OWASP: https://www.owasp.org/index.php/Certificate_and_Public_Key_Pinning Doc: https://developer.mozilla.org/de/docs/Web/Security/Public_Key_Pinning RFC: https://tools.ietf.org/html/draft-ietf-websec-key-pinning-21

14. GnuTLS

14.1 SSL engine stuff

Is this even possible?

14.2 check connection

Add a way to check if the connection seems to be alive, to correspond to the SSL_peak() way we use with OpenSSL.

15. WinSSL/SChannel

15.1 Add support for client certificate authentication

WinSSL/SChannel currently makes use of the OS-level system and user certificate and private key stores. This does not allow the application or the user to supply a custom client certificate using curl or libcurl.

Therefore support for the existing -E/--cert and --key options should be implemented by supplying a custom certificate to the SChannel APIs, see: - Getting a Certificate for Schannel

https://msdn.microsoft.com/en-us/library/windows/desktop/aa375447.aspx

15.2 Add support for custom server certificate validation

WinSSL/SChannel currently makes use of the OS-level system and user certificate trust store. This does not allow the application or user to customize the server certificate validation process using curl or libcurl.

Therefore support for the existing --cacert or --capath options should be implemented by supplying a custom certificate to the SChannel APIs, see: - Getting a Certificate for Schannel

https://msdn.microsoft.com/en-us/library/windows/desktop/aa375447.aspx

15.3 Add support for the --ciphers option

The cipher suites used by WinSSL/SChannel are configured on an OS-level instead of an application-level. This does not allow the application or the user to customize the configured cipher suites using curl or libcurl.

Therefore support for the existing --ciphers option should be implemented by mapping the OpenSSL/GnuTLS cipher suites to the SChannel APIs, see - Specifying Schannel Ciphers and Cipher Strengths

https://msdn.microsoft.com/en-us/library/windows/desktop/aa380161.aspx

16. SASL

16.1 Other authentication mechanisms

Add support for other authentication mechanisms such as OLP, GSS-SPNEGO and others.

16.2 Add QOP support to GSSAPI authentication

Currently the GSSAPI authentication only supports the default QOP of auth (Authentication), whilst Kerberos V5 supports both auth-int (Authentication with integrity protection) and auth-conf (Authentication with integrity and privacy protection).

16.3 Support binary messages (i.e.: non-base64)

Mandatory to support LDAP SASL authentication.

17. SSH protocols

17.1 Multiplexing

SSH is a perfectly fine multiplexed protocols which would allow libcurl to do multiple parallel transfers from the same host using the same connection, much in the same spirit as HTTP/2 does. libcurl however does not take advantage of that ability but will instead always create a new connection for new transfers even if an existing connection already exists to the host.

To fix this, libcurl would have to detect an existing connection and "attach" the new transfer to the existing one.

17.2 SFTP performance

libcurl's SFTP transfer performance is sub par and can be improved, mostly by the approach mentioned in "1.6 Modified buffer size approach".

17.3 Support better than MD5 hostkey hash

libcurl offers the CURLOPT_SSH_HOST_PUBLIC_KEY_MD5 option for verifying the server's key. MD5 is generally being deprecated so we should implement support for stronger hashing algorithms. libssh2 itself is what provides this underlying functionality and it supports at least SHA-1 as an alternative. SHA-1 is also being deprecated these days so we should consider workign with libssh2 to instead offer support for SHA-256 or similar.

18. Command line tool

18.1 sync

"curl --sync http://example.com/feed[1-100].rss" or "curl --sync http://example.net/{index,calendar,history}.html"

Downloads a range or set of URLs using the remote name, but only if the remote file is newer than the local file. A Last-Modified HTTP date header should also be used to set the mod date on the downloaded file.

18.2 glob posts

Globbing support for -d and -F, as in 'curl -d "name=foo[0-9]" URL'. This is easily scripted though.

18.3 prevent file overwriting

Add an option that prevents curl from overwriting existing local files. When used, and there already is an existing file with the target file name (either -O or -o), a number should be appended (and increased if already existing). So that index.html becomes first index.html.1 and then index.html.2 etc.

18.4 simultaneous parallel transfers

The client could be told to use maximum N simultaneous parallel transfers and then just make sure that happens. It should of course not make more than one connection to the same remote host. This would require the client to use the multi interface. https://curl.haxx.se/bug/feature.cgi?id=1558595

Using the multi interface would also allow properly using parallel transfers with HTTP/2 and supporting HTTP/2 server push from the command line.

18.5 provide formpost headers

Extending the capabilities of the multipart formposting. How about leaving the ';type=foo' syntax as it is and adding an extra tag (headers) which works like this: curl -F "coolfiles=@fil1.txt;headers=@fil1.hdr" where fil1.hdr contains extra headers like

Content-Type: text/plain; charset=KOI8-R" Content-Transfer-Encoding: base64 X-User-Comment: Please don't use browser specific HTML code

which should overwrite the program reasonable defaults (plain/text, 8bit...)

18.6 warning when setting an option

Display a warning when libcurl returns an error when setting an option. This can be useful to tell when support for a particular feature hasn't been compiled into the library.

18.7 warning when sending binary output to terminal

Provide a way that prompts the user for confirmation before binary data is sent to the terminal, much in the style 'less' does it.

18.8 offer color-coded HTTP header output

By offering different color output on the header name and the header contents, they could be made more readable and thus help users working on HTTP services.

18.9 Choose the name of file in braces for complex URLs

When using braces to download a list of URLs and you use complicated names in the list of alternatives, it could be handy to allow curl to use other names when saving.

Consider a way to offer that. Possibly like {partURL1:name1,partURL2:name2,partURL3:name3} where the name following the colon is the output name.

See https://github.com/curl/curl/issues/221

18.10 improve how curl works in a windows console window

If you pull the scrollbar when transferring with curl in a Windows console window, the transfer is interrupted and can get disconnected. This can probably be improved. See https://github.com/curl/curl/issues/322

18.11 -w output to stderr

-w is quite useful, but not to those of us who use curl without -o or -O (such as for scripting through a higher level language). It would be nice to have an option that is exactly like -w but sends it to stderr instead. Proposed name: --write-stderr. See https://github.com/curl/curl/issues/613

18.12 keep running, read instructions from pipe/socket

Provide an option that makes curl not exit after the last URL (or even work without a given URL), and then make it read instructions passed on a pipe or over a socket to make further instructions so that a second subsequent curl invoke can talk to the still running instance and ask for transfers to get done, and thus maintain its connection pool, DNS cache and more.

18.13 support metalink in http headers

Curl has support for downloading a metalink xml file, processing it, and then downloading the target of the metalink. This is done via the --metalink option. It would be nice if metalink also supported downloading via metalink information that is stored in HTTP headers (RFC 6249). Theoretically this could also be supported with the --metalink option.

See https://tools.ietf.org/html/rfc6249

See also https://lists.gnu.org/archive/html/bug-wget/2015-06/msg00034.html for an implematation of this in wget.

18.14 --fail without --location should treat 3xx as a failure

To allow a command line like this to detect a redirect and consider it a failure:

curl -v --fail -O https://example.com/curl-7.48.0.tar.gz

... --fail must treat 3xx responses as failures too. The least problematic way to implement this is probably to add that new logic in the command line tool only and not in the underlying CURLOPT_FAILONERROR logic.

18.15 Introduce --fail-fast to exit on first transfer fail

curl will transfer all URLs given on the command line one by one but only returns the error code for the last transfer. Transfer failures on the first ones will not be returned as error code etc to the shell. A --fail-fast option would make curl exit and return an error for the first transfer that fails.

18.16 --retry should resume

When --retry is used and curl actually retries transfer, it should use the already transfered data and do a resumed transfer for the rest (when possible) so that it doesn't have to transfer the same data again that was already tranfered before the retry.

See https://github.com/curl/curl/issues/1084

19. Build

19.1 roffit

Consider extending 'roffit' to produce decent ASCII output, and use that instead of (g)nroff when building src/tool_hugehelp.c

19.2 Enable PIE and RELRO by default

Especially when having programs that execute curl via the command line, PIE renders the exploitation of memory corruption vulnerabilities a lot more difficult. This can be attributed to the additional information leaks being required to conduct a successful attack. RELRO, on the other hand, masks different binary sections like the GOT as read-only and thus kills a handful of techniques that come in handy when attackers are able to arbitrarily overwrite memory. A few tests showed that enabling these features had close to no impact, neither on the performance nor on the general functionality of curl.

20. Test suite

20.1 SSL tunnel

Make our own version of stunnel for simple port forwarding to enable HTTPS and FTP-SSL tests without the stunnel dependency, and it could allow us to provide test tools built with either OpenSSL or GnuTLS

20.2 nicer lacking perl message

If perl wasn't found by the configure script, don't attempt to run the tests but explain something nice why it doesn't.

20.3 more protocols supported

Extend the test suite to include more protocols. The telnet could just do FTP or http operations (for which we have test servers).

20.4 more platforms supported

Make the test suite work on more platforms. OpenBSD and Mac OS. Remove fork()s and it should become even more portable.

20.5 Add support for concurrent connections

Tests 836, 882 and 938 were designed to verify that separate connections aren't used when using different login credentials in protocols that shouldn't re-use a connection under such circumstances.

Unfortunately, ftpserver.pl doesn't appear to support multiple concurrent connections. The read while() loop seems to loop until it receives a disconnect from the client, where it then enters the waiting for connections loop. When the client opens a second connection to the server, the first connection hasn't been dropped (unless it has been forced - which we shouldn't do in these tests) and thus the wait for connections loop is never entered to receive the second connection.

20.6 Use the RFC6265 test suite

A test suite made for HTTP cookies (RFC 6265) by Adam Barth is available at https://github.com/abarth/http-state/tree/master/tests

It'd be really awesome if someone would write a script/setup that would run curl with that test suite and detect deviances. Ideally, that would even be incorporated into our regular test suite.

21. Next SONAME bump

21.1 http-style HEAD output for FTP

#undef CURL_FTP_HTTPSTYLE_HEAD in lib/ftp.c to remove the HTTP-style headers from being output in NOBODY requests over FTP

21.2 combine error codes

Combine some of the error codes to remove duplicates. The original numbering should not be changed, and the old identifiers would be macroed to the new ones in an CURL_NO_OLDIES section to help with backward compatibility.

Candidates for removal and their replacements:

CURLE_FILE_COULDNT_READ_FILE => CURLE_REMOTE_FILE_NOT_FOUND

CURLE_FTP_COULDNT_RETR_FILE => CURLE_REMOTE_FILE_NOT_FOUND

CURLE_FTP_COULDNT_USE_REST => CURLE_RANGE_ERROR

CURLE_FUNCTION_NOT_FOUND => CURLE_FAILED_INIT

CURLE_LDAP_INVALID_URL => CURLE_URL_MALFORMAT

CURLE_TFTP_NOSUCHUSER => CURLE_TFTP_ILLEGAL

CURLE_TFTP_NOTFOUND => CURLE_REMOTE_FILE_NOT_FOUND

CURLE_TFTP_PERM => CURLE_REMOTE_ACCESS_DENIED

21.3 extend CURLOPT_SOCKOPTFUNCTION prototype

The current prototype only provides 'purpose' that tells what the connection/socket is for, but not any protocol or similar. It makes it hard for applications to differentiate on TCP vs UDP and even HTTP vs FTP and similar.

22. Next major release

22.1 cleanup return codes

curl_easy_cleanup() returns void, but curl_multi_cleanup() returns a CURLMcode. These should be changed to be the same.

22.2 remove obsolete defines

remove obsolete defines from curl/curl.h

22.3 size_t

make several functions use size_t instead of int in their APIs

22.4 remove several functions

remove the following functions from the public API:

curl_getenv

curl_mprintf (and variations)

curl_strequal

curl_strnequal

They will instead become curlx_ - alternatives. That makes the curl app still capable of using them, by building with them from source.

These functions have no purpose anymore:

curl_multi_socket

curl_multi_socket_all

22.5 remove CURLOPT_FAILONERROR

Remove support for CURLOPT_FAILONERROR, it has gotten too kludgy and weird internally. Let the app judge success or not for itself.

22.6 remove CURLOPT_DNS_USE_GLOBAL_CACHE

Remove support for a global DNS cache. Anything global is silly, and we already offer the share interface for the same functionality but done "right".

22.7 remove progress meter from libcurl

The internally provided progress meter output doesn't belong in the library. Basically no application wants it (apart from curl) but instead applications can and should do their own progress meters using the progress callback.

The progress callback should then be bumped as well to get proper 64bit variable types passed to it instead of doubles so that big files work correctly.

22.8 remove 'curl_httppost' from public

curl_formadd() was made to fill in a public struct, but the fact that the struct is public is never really used by application for their own advantage but instead often restricts how the form functions can or can't be modified.

Changing them to return a private handle will benefit the implementation and allow us much greater freedoms while still maintaining a solid API and ABI.