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Things that could be nice to do in the future
Things to do in project curl. Please tell us what you think, contribute and
send us patches that improve things!
Be aware that these are things that we could do, or have once been considered
things we could do. If you want to work on any of these areas, please
consider bringing it up for discussions first on the mailing list so that we
all agree it is still a good idea for the project!
All bugs documented in the KNOWN_BUGS document are subject for fixing!
1. libcurl
1.1 TFO support on Windows
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 Support HTTP/2 for HTTP(S) proxies
1.8 CURLOPT_RESOLVE for any port number
1.9 Cache negative name resolves
1.10 auto-detect proxy
1.11 minimize dependencies with dynamically loaded modules
1.12 updated DNS server while running
1.13 c-ares and CURLOPT_OPENSOCKETFUNCTION
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
1.20 SRV and URI DNS records
1.21 Have the URL API offer IDN decoding
1.22 CURLINFO_PAUSE_STATE
1.23 Offer API to flush the connection pool
1.24 TCP Fast Open for windows
1.25 Expose tried IP addresses that failed
1.26 CURL_REFUSE_CLEARTEXT
1.27 hardcode the "localhost" addresses
1.28 FD_CLOEXEC
1.29 Upgrade to websockets
1.30 config file parsing
2. 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
2.6 multi upkeep
3. Documentation
3.2 Provide cmake config-file
4. 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
4.8 Option to ignore private IP addresses in PASV response
5. HTTP
5.1 Better persistency for HTTP 1.0
5.2 support FF3 sqlite cookie files
5.3 Rearrange request header order
5.4 Allow SAN names in HTTP/2 server push
5.5 auth= in URLs
5.6 Refuse "downgrade" redirects
5.7 QUIC
6. TELNET
6.1 ditch stdin
6.2 ditch telnet-specific select
6.3 feature negotiation debug data
7. SMTP
7.1 Pipelining
7.2 Enhanced capability support
7.3 Add CURLOPT_MAIL_CLIENT option
8. POP3
8.1 Pipelining
8.2 Enhanced capability support
9. IMAP
9.1 Enhanced capability support
10. LDAP
10.1 SASL based authentication mechanisms
11. SMB
11.1 File listing support
11.2 Honor file timestamps
11.3 Use NTLMv2
11.4 Create remote directories
12. New protocols
12.1 RSYNC
13. SSL
13.1 Disable specific versions
13.2 Provide mutex locking API
13.3 Support in-memory certs/ca certs/keys
13.4 Cache/share 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 Configurable loading of OpenSSL configuration file
13.10 Support Authority Information Access certificate extension (AIA)
13.11 Support intermediate & root pinning for PINNEDPUBLICKEY
13.12 Support HSTS
13.13 Support HPKP
13.14 Support the clienthello extension
14. GnuTLS
14.1 SSL engine stuff
14.2 check connection
15. WinSSL/SChannel
15.1 Add support for client certificate authentication
15.3 Add support for the --ciphers option
15.4 Add option to disable client certificate auto-send
16. SASL
16.1 Other authentication mechanisms
16.2 Add QOP support to GSSAPI authentication
16.3 Support binary messages (i.e.: non-base64)
17. SSH protocols
17.1 Multiplexing
17.2 SFTP performance
17.3 Support better than MD5 hostkey hash
17.4 Support CURLOPT_PREQUOTE
18. Command line tool
18.1 sync
18.2 glob posts
18.3 prevent file overwriting
18.4 simultaneous parallel transfers
18.5 UTF-8 filenames in Content-Disposition
18.6 warning when setting an option
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 Windows: set attribute 'archive' for completed downloads
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 --retry should resume
18.16 send only part of --data
18.17 consider file name from the redirected URL with -O ?
18.18 retry on network is unreachable
18.19 expand ~/ in config files
18.20 host name sections in config files
19. Build
19.1 roffit
19.2 Enable PIE and RELRO by default
19.3 cmake test suite improvements
20. 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
20.7 Support LD_PRELOAD on macOS
21. Next SONAME bump
21.1 http-style HEAD output for FTP
21.2 combine error codes
21.3 extend CURLOPT_SOCKOPTFUNCTION prototype
22. 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
22.7 remove progress meter from libcurl
22.8 remove 'curl_httppost' from public
==============================================================================
1. libcurl
1.1 TFO support on Windows
TCP Fast Open is supported on several platforms but not on Windows. Work on
this was once started but never finished.
See https://github.com/curl/curl/pull/3378
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.
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:
https://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 Support HTTP/2 for HTTP(S) proxies
Support for doing HTTP/2 to HTTP and HTTPS proxies is still missing.
See https://github.com/curl/curl/issues/3570
1.8 CURLOPT_RESOLVE for any port number
This option allows applications to set a replacement IP address for a given
host + port pair. Consider making support for providing a replacement address
for the host name on all port numbers.
See https://github.com/curl/curl/issues/1264
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.
1.10 auto-detect proxy
libcurl could be made to detect the system proxy setup automatically and use
that. On Windows, macOS and Linux desktops for example.
The pull-request to use libproxy for this was deferred due to doubts on the
reliability of the dependency and how to use it:
https://github.com/curl/curl/pull/977
libdetectproxy is a (C++) library for detecting the proxy on Windows
https://github.com/paulharris/libdetectproxy
1.11 minimize dependencies with dynamically 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 updated DNS server while running
If /etc/resolv.conf gets updated while a program using libcurl is running, it
is may cause name resolves to fail unless res_init() is called. We should
consider calling res_init() + retry once unconditionally on all name resolve
failures to mitigate against this. Firefox works like that. Note that Windows
doesn't have res_init() or an alternative.
https://github.com/curl/curl/issues/2251
1.13 c-ares and CURLOPT_OPENSOCKETFUNCTION
curl will create most sockets via the CURLOPT_OPENSOCKETFUNCTION callback and
close them with the CURLOPT_CLOSESOCKETFUNCTION callback. However, c-ares
does not use those functions and instead opens and closes the sockets
itself. This means that when curl passes the c-ares socket to the
CURLMOPT_SOCKETFUNCTION it isn't owned by the application like other sockets.
See https://github.com/curl/curl/issues/2734
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
1.20 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 Have the URL API offer IDN decoding
Similar to how URL decoding/encoding is done, we could have URL functions to
convert IDN host names to punycode (probably not the reverse).
https://github.com/curl/curl/issues/3232
1.22 CURLINFO_PAUSE_STATE
Return information about the transfer's current pause state, in both
directions. https://github.com/curl/curl/issues/2588
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 Expose tried IP addresses that failed
When libcurl fails to connect to a host, it should be able to offer the
application the list of IP addresses that were used in the attempt.
https://github.com/curl/curl/issues/2126
1.26 CURL_REFUSE_CLEARTEXT
An environment variable that when set will make libcurl refuse to use any
cleartext network protocol. That's all non-encrypted ones (FTP, HTTP, Gopher,
etc). By adding the check to libcurl and not just curl, this environment
variable can then help users to block all libcurl-using programs from
accessing the network using unsafe protocols.
The variable could be given some sort of syntax or different levels and be
used to also allow for example users to refuse libcurl to do transfers with
HTTPS certificate checks disabled.
It could also automatically refuse usernames in URLs when set
(see CURLOPT_DISALLOW_USERNAME_IN_URL)
1.27 hardcode the "localhost" addresses
There's this new spec getting adopted that says "localhost" should always and
unconditionally be a local address and not get resolved by a DNS server. A
fine way for curl to fix this would be to simply hard-code the response to
127.0.0.1 and/or ::1 (depending on what IP versions that are requested). This
is what the browsers probably will do with this hostname.
https://bugzilla.mozilla.org/show_bug.cgi?id=1220810
https://tools.ietf.org/html/draft-ietf-dnsop-let-localhost-be-localhost-02
1.28 FD_CLOEXEC
It sets the close-on-exec flag for the file descriptor, which causes the file
descriptor to be automatically (and atomically) closed when any of the
exec-family functions succeed. Should probably be set by default?
https://github.com/curl/curl/issues/2252
1.29 Upgrade to websockets
libcurl could offer a smoother path to get to a websocket connection.
See https://github.com/curl/curl/issues/3523
Michael Kaufmann suggestion here:
https://curl.haxx.se/video/curlup-2017/2017-03-19_05_Michael_Kaufmann_Websocket_support_for_curl.mp4
1.30 config file parsing
Consider providing an API, possibly in a separate companion library, for
parsing a config file like curl's -K/--config option to allow applications to
get the same ability to read curl options from files.
See https://github.com/curl/curl/issues/3698
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 or the threaded resolver is used
- 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().
2.6 multi upkeep
In libcurl 7.62.0 we introduced curl_easy_upkeep. It unfortunately only works
on easy handles. We should introduces a version of that for the multi handle,
and also consider doing "upkeep" automatically on connections in the
connection pool when the multi handle is in used.
See https://github.com/curl/curl/issues/3199
3. Documentation
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: https://www.nsftools.com/tips/RawFTP.htm#STAT
This is not detailed in any FTP specification.
4.8 Option to ignore private IP addresses in PASV response
Some servers respond with and some other FTP client implementations can
ignore private (RFC 1918 style) IP addresses when received in PASV responses.
To consider for libcurl as well. See https://github.com/curl/curl/issues/1455
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.
5.4 Allow SAN names in HTTP/2 server push
curl only allows HTTP/2 push promise if the provided :authority header value
exactly matches the host name given in the URL. It could be extended to allow
any name that would match the Subject Alternative Names in the server's TLS
certificate.
See https://github.com/curl/curl/pull/3581
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 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.
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.
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 Support in-memory certs/ca certs/keys
You can specify the private and public keys for SSH/SSL as file paths. Some
programs want to avoid using files and instead just pass them as in-memory
data blobs. There's probably a challenge to make this work across the
plethory of different TLS and SSH backends that curl supports.
https://github.com/curl/curl/issues/2310
13.4 Cache/share 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.
Technically, the "caching" is probably best implemented by getting added to
the share interface so that easy handles who want to and can reuse the
context specify that by sharing with the right properties set.
https://github.com/curl/curl/issues/1110
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 Configurable loading of OpenSSL configuration file
libcurl calls the OpenSSL function CONF_modules_load_file() in openssl.c,
Curl_ossl_init(). "We regard any changes in the OpenSSL configuration as a
security risk or at least as unnecessary."
Please add a configuration switch or something similar to disable the
CONF_modules_load_file() call.
See https://github.com/curl/curl/issues/2724
13.10 Support Authority Information Access certificate extension (AIA)
AIA can provide various things like CRLs but more importantly information
about intermediate CA certificates that can allow validation path to be
fulfilled when the HTTPS server doesn't itself provide them.
Since AIA is about downloading certs on demand to complete a TLS handshake,
it is probably a bit tricky to get done right.
See https://github.com/curl/curl/issues/2793
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
13.14 Support the clienthello extension
Certain stupid networks and middle boxes have a problem with SSL handshake
pakets that are within a certain size range because how that sets some bits
that previously (in older TLS version) were not set. The clienthello
extension adds padding to avoid that size range.
https://tools.ietf.org/html/rfc7685
https://github.com/curl/curl/issues/2299
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
15.3 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
15.4 Add option to disable client certificate auto-send
Microsoft says "By default, Schannel will, with no notification to the client,
attempt to locate a client certificate and send it to the server." That could
be considered a privacy violation and unexpected.
Some Windows users have come to expect that default behavior and to change the
default to make it consistent with other SSL backends would be a breaking
change. An option should be added that can be used to disable the default
Schannel auto-send behavior.
https://github.com/curl/curl/issues/2262
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 working with
libssh2 to instead offer support for SHA-256 or similar.
17.4 Support CURLOPT_PREQUOTE
The two other QUOTE options are supported for SFTP, but this was left out for
unknown reasons!
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 UTF-8 filenames in Content-Disposition
RFC 6266 documents how UTF-8 names can be passed to a client in the
Content-Disposition header, and curl does not support this.
https://github.com/curl/curl/issues/1888
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.
18.8 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 Windows: set attribute 'archive' for completed downloads
The archive bit (FILE_ATTRIBUTE_ARCHIVE, 0x20) separates files that shall be
backed up from those that are either not ready or have not changed.
Downloads in progress are neither ready to be backed up, nor should they be
opened by a different process. Only after a download has been completed it's
sensible to include it in any integer snapshot or backup of the system.
See https://github.com/curl/curl/issues/3354
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 --retry should resume
When --retry is used and curl actually retries transfer, it should use the
already transferred 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 transferred before the retry.
See https://github.com/curl/curl/issues/1084
18.16 send only part of --data
When the user only wants to send a small piece of the data provided with
--data or --data-binary, like when that data is a huge file, consider a way
to specify that curl should only send a piece of that. One suggested syntax
would be: "--data-binary @largefile.zip!1073741823-2147483647".
See https://github.com/curl/curl/issues/1200
18.17 consider file name from the redirected URL with -O ?
When a user gives a URL and uses -O, and curl follows a redirect to a new
URL, the file name is not extracted and used from the newly redirected-to URL
even if the new URL may have a much more sensible file name.
This is clearly documented and helps for security since there's no surprise
to users which file name that might get overwritten. But maybe a new option
could allow for this or maybe -J should imply such a treatment as well as -J
already allows for the server to decide what file name to use so it already
provides the "may overwrite any file" risk.
This is extra tricky if the original URL has no file name part at all since
then the current code path will error out with an error message, and we can't
*know* already at that point if curl will be redirected to a URL that has a
file name...
See https://github.com/curl/curl/issues/1241
18.18 retry on network is unreachable
The --retry option retries transfers on "transient failures". We later added
--retry-connrefused to also retry for "connection refused" errors.
Suggestions have been brought to also allow retry on "network is unreachable"
errors and while totally reasonable, maybe we should consider a way to make
this more configurable than to add a new option for every new error people
want to retry for?
https://github.com/curl/curl/issues/1603
18.19 expand ~/ in config files
For example .curlrc could benefit from being able to do this.
See https://github.com/curl/curl/issues/2317
18.20 host name sections in config files
config files would be more powerful if they could set different
configurations depending on used URLs, host name or possibly origin. Then a
default .curlrc could a specific user-agent only when doing requests against
a certain site.
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.
19.3 cmake test suite improvements
The cmake build doesn't support 'make show' so it doesn't know which tests
are in the makefile or not (making appveyor builds do many false warnings
about it) nor does it support running the test suite if building out-of-tree.
See https://github.com/curl/curl/issues/3109
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.
20.7 Support LD_PRELOAD on macOS
LD_RELOAD doesn't work on macOS, but there are tests which require it to run
properly. Look into making the preload support in runtests.pl portable such
that it uses DYLD_INSERT_LIBRARIES on macOS.
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.
22.7 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.
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