lib/src: white space edits to comply better with code style

... as checksrc now finds and complains about these.

Closes #14921

lib, src, tests: added space around ternary expressions

Closes #14912

vtls/rustls: support strong CSRNG data

Now that the curl rustls vtls backend is using rustls 0.14 we can
address the weak random situation by using
`rustls_default_crypto_provider_ra

vtls/rustls: support strong CSRNG data

Now that the curl rustls vtls backend is using rustls 0.14 we can
address the weak random situation by using
`rustls_default_crypto_provider_random()` to provide a `Curl_ssl`
`random` callback that fills the provided buffer with cryptographically
secure random data.

The mentions in `docs/` about weak RNG when using rustls are removed as
they are no longer applicable.

Closes #14889

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vtls/rustls: simplify ciphersuite skipping

Now that the rustls vtls backend is using rustls 0.14 we can take
advantage of `rustls_supported_ciphersuite_protocol_version()` to skip
TL

vtls/rustls: simplify ciphersuite skipping

Now that the rustls vtls backend is using rustls 0.14 we can take
advantage of `rustls_supported_ciphersuite_protocol_version()` to skip
TLS 1.3 and TLS 1.2 ciphersuites as required without needing to
interrogate the ciphersuite names as `rustls_str`s.

Closes #14889

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vtls/rustls: rustls-ffi 0.14.0 update

* Documentation is updated to describe new required version, and to link
to the upstream README about cryptography providers.
* GitHub workflo

vtls/rustls: rustls-ffi 0.14.0 update

* Documentation is updated to describe new required version, and to link
to the upstream README about cryptography providers.
* GitHub workflow is updated to fetch 0.14.0.
* Breaking changes in`lib/vtls/rustls.c` are addressed:
* The `rustls_client_config_builder_build()` function now uses an out
parameter for the built config instead of returning it directly.
This allows the building process to fail if the default crypto
provider state isn't appropriate, or another error condition occurs.
* Default ciphersuites are collected using renamed functions named to
make it clear the ciphersuites are associated with the default
crypto provider.
* Customization of ciphersuites is now done via
a `rustls_crypto_provider_builder` used to instantiate a
`rustls_crypto_provider`. The customized provider can then can be
used with `rustls_client_config_builder_new_custom` in place of
providing ciphersuites directly.
* `rustls_connection_get_negotiated_ciphersuite()` now returns the
ciphersuite ID directly.

Closes #14889

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vtls/rustls: differentiate error messages

It's easier to diagnose a problem when there is one place where the
error message can be emitted. For that reason this commit updates two
er

vtls/rustls: differentiate error messages

It's easier to diagnose a problem when there is one place where the
error message can be emitted. For that reason this commit updates two
errors that were shared between other fallible operations to use unique
messages.

Closes #14889

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vtls/rustls: simplify builder cleanup

Don't build `config_builder` just to free the resulting config, free the
builder directly.

When `cr_init_backend` encounters an error condi

vtls/rustls: simplify builder cleanup

Don't build `config_builder` just to free the resulting config, free the
builder directly.

When `cr_init_backend` encounters an error condition setting up the
Rustls client configuration it must do something with the
`config_builder` that was constructed earlier to avoid a memory leak.

The previous implementation preferred to use a pattern of building the
builder (thus consuming it) and then freeing the built config (to avoid
a memory leak). However, the purpose/intent is clearer when we just free
the builder directly instead of building it and freeing the result.

Closes #14889

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rustls: fixed minor logic bug in default cipher selection

Follow-up to 1e03d4b

Closes #14840

lib: use FMT_ as prefix instead of CURL_FORMAT_

For printf format defines used internally. Makes the code slighly
easier to read.

Closes #14764

rand: only provide weak random when needed

builds without TLS and builds using rustls

Closes #14749

tidy-up: spelling quiche and Rustls

Closes #14605

rustls: fix setting tls version

The value CURL_SSLVERSION_TLSv1_0 was unsupported.

Closes #14586

rustls: add support for setting TLS version and ciphers

Add support for CURLOPT_SSLVERSION, CURLOPT_TLS13_CIPHERS and
CURLOPT_SSL_CIPHER_LIST.

Closes #14535

spnego_gssapi: implement TLS channel bindings for openssl

Channel Bindings are used to tie the session context to a specific TLS
channel. This is to provide additional proof of valid ide

spnego_gssapi: implement TLS channel bindings for openssl

Channel Bindings are used to tie the session context to a specific TLS
channel. This is to provide additional proof of valid identity,
mitigating authentication relay attacks.

Major web servers have the ability to require (None/Accept/Require)
GSSAPI channel binding, rendering Curl unable to connect to such
websites unless support for channel bindings is implemented.

IIS calls this feature Extended Protection (EPA), which is used in
Enterprise environments using Kerberos for authentication.

This change require krb5 >= 1.19, otherwise channel bindings won't be
forwarded through SPNEGO.

Co-Authored-By: Steffen Kieß <947515+steffen-kiess@users.noreply.github.com>
Closes #13098

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lib: add eos flag to send methods

Adds a `bool eos` flag to send methods to indicate that the data
is the last chunk the invovled transfer wants to send to the server.

This will

lib: add eos flag to send methods

Adds a `bool eos` flag to send methods to indicate that the data
is the last chunk the invovled transfer wants to send to the server.

This will help protocol filters like HTTP/2 and 3 to forward the
stream's EOF flag and also allow to EAGAIN such calls when buffers
are not yet fully flushed.

Closes #14220

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rustls: make all tests pass

- supports IP addresses in certs since 0.21
- Remove workaround, and re-enable tests

Closes #14317

Revert "lib: send eos flag"

This reverts commit be93299f10ef0b2bf7fe5c82140120073831867a.

lib: send eos flag

Adds a `bool eos` flag to send methods to indicate that the data is the
last chunk the invovled transfer wants to send to the server.

This will help protocol

lib: send eos flag

Adds a `bool eos` flag to send methods to indicate that the data is the
last chunk the invovled transfer wants to send to the server.

This will help protocol filters like HTTP/2 and 3 to forward the
stream's EOF flag and also allow to EAGAIN such calls when buffers are
not yet fully flushed.

Closes #14220

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code: language cleanup in comments

Based on the standards and guidelines we use for our documentation.

- expand contractions (they're => they are etc)
- host name = > hostname

code: language cleanup in comments

Based on the standards and guidelines we use for our documentation.

- expand contractions (they're => they are etc)
- host name = > hostname
- file name => filename
- user name = username
- man page => manpage
- run-time => runtime
- set-up => setup
- back-end => backend
- a HTTP => an HTTP
- Two spaces after a period => one space after period

Closes #14073

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lib: graceful connection shutdown

When libcurl discards a connection there are two phases this may go
through: "shutdown" and "closing". If a connection is aborted, the
shutdown phas

lib: graceful connection shutdown

When libcurl discards a connection there are two phases this may go
through: "shutdown" and "closing". If a connection is aborted, the
shutdown phase is skipped and it is closed right away.

The connection filters attached to the connection implement the phases
in their `do_shutdown()` and `do_close()` callbacks. Filters carry now a
`shutdown` flags next to `connected` to keep track of the shutdown
operation.

Filters are shut down from top to bottom. If a filter is not connected,
its shutdown is skipped. Notable filters that *do* something during
shutdown are HTTP/2 and TLS. HTTP/2 sends the GOAWAY frame. TLS sends
its close notify and expects to receive a close notify from the server.

As sends and receives may EAGAIN on the network, a shutdown is often not
successful right away and needs to poll the connection's socket(s). To
facilitate this, such connections are placed on a new shutdown list
inside the connection cache.

Since managing this list requires the cooperation of a multi handle,
only the connection cache belonging to a multi handle is used. If a
connection was in another cache when being discarded, it is removed
there and added to the multi's cache. If no multi handle is available at
that time, the connection is shutdown and closed in a one-time,
best-effort attempt.

When a multi handle is destroyed, all connection still on the shutdown
list are discarded with a final shutdown attempt and close. In curl
debug builds, the environment variable `CURL_GRACEFUL_SHUTDOWN` can be
set to make this graceful with a timeout in milliseconds given by the
variable.

The shutdown list is limited to the max number of connections configured
for a multi cache. Set via CURLMOPT_MAX_TOTAL_CONNECTIONS. When the
limit is reached, the oldest connection on the shutdown list is
discarded.

- In multi_wait() and multi_waitfds(), collect all connection caches
involved (each transfer might carry its own) into a temporary list.
Let each connection cache on the list contribute sockets and
POLLIN/OUT events it's connections are waiting for.

- in multi_perform() collect the connection caches the same way and let
them peform their maintenance. This will make another non-blocking
attempt to shutdown all connections on its shutdown list.

- for event based multis (multi->socket_cb set), add the sockets and
their poll events via the callback. When `multi_socket()` is invoked
for a socket not known by an active transfer, forward this to the
multi's cache for processing. On closing a connection, remove its
socket(s) via the callback.

TLS connection filters MUST NOT send close nofity messages in their
`do_close()` implementation. The reason is that a TLS close notify
signals a success. When a connection is aborted and skips its shutdown
phase, the server needs to see a missing close notify to detect
something has gone wrong.

A graceful shutdown of FTP's data connection is performed implicitly
before regarding the upload/download as complete and continuing on the
control connection. For FTP without TLS, there is just the socket close
happening. But with TLS, the sent/received close notify signals that the
transfer is complete and healthy. Servers like `vsftpd` verify that and
reject uploads without a TLS close notify.

- added test_19_* for shutdown related tests
- test_19_01 and test_19_02 test for TCP RST packets
which happen without a graceful shutdown and should
no longer appear otherwise.
- add test_19_03 for handling shutdowns by the server
- add test_19_04 for handling shutdowns by curl
- add test_19_05 for event based shutdowny by server
- add test_30_06/07 and test_31_06/07 for shutdown checks
on FTP up- and downloads.

Closes #13976

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connection: shutdown TLS (for FTP) better

This adds connection shutdown infrastructure and first use for FTP. FTP
data connections, when not encountering an error, are now shut down in a

connection: shutdown TLS (for FTP) better

This adds connection shutdown infrastructure and first use for FTP. FTP
data connections, when not encountering an error, are now shut down in a
blocking way with a 2sec timeout.

- add cfilter `Curl_cft_shutdown` callback
- keep a shutdown start timestamp and timeout at connectdata
- provide shutdown timeout default and member in
`data->set.shutdowntimeout`.
- provide methods for starting, interrogating and clearing
shutdown timers
- provide `Curl_conn_shutdown_blocking()` to shutdown the
`sockindex` filter chain in a blocking way. Use that in FTP.
- add `Curl_conn_cf_poll()` to wait for socket events during
shutdown of a connection filter chain.
This gets the monitoring sockets and events via the filters
"adjust_pollset()" methods. This gives correct behaviour when
shutting down a TLS connection through a HTTP/2 proxy.
- Implement shutdown for all socket filters
- for HTTP/2 and h2 proxying to send GOAWAY
- for TLS backends to the best of their capabilities
- for tcp socket filter to make a final, nonblocking
receive to avoid unwanted RST states
- add shutdown forwarding to happy eyeballers and
https connect ballers when applicable.

Closes #13904

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vtls: new io_need flags for poll handling

- decouple need to recv/send from negotiation state, we need
this later in shutdown handling as well
- move ssl enums from urldata.h to vt

vtls: new io_need flags for poll handling

- decouple need to recv/send from negotiation state, we need
this later in shutdown handling as well
- move ssl enums from urldata.h to vtls_int.h
- implement use of `connssl->io_need` in vtls.c. and all backends

Closes #13879

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lib/v*: tidy up types and casts

Also add a couple of negative checks.

Cherry-picked from #13489
Closes #13622

multi: add multi->proto_hash, a key-value store for protocol data

- add `Curl_hash_add2()` that passes a destructor function for
the element added. Call element destructor instead of h

multi: add multi->proto_hash, a key-value store for protocol data

- add `Curl_hash_add2()` that passes a destructor function for
the element added. Call element destructor instead of hash
destructor if present.
- multi: add `proto_hash` for protocol related information,
remove `struct multi_ssl_backend_data`.
- openssl: use multi->proto_hash to keep x509 shared store
- schannel: use multi->proto_hash to keep x509 shared store
- vtls: remove Curl_free_multi_ssl_backend_data() and its
equivalents in the TLS backends

Closes #13345

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rustls: fix handshake done handling

- rustls report it has finished the TLS handshake *before*
all relevant data has been sent off, e.g. it FINISHED message
- On connections the se

rustls: fix handshake done handling

- rustls report it has finished the TLS handshake *before*
all relevant data has been sent off, e.g. it FINISHED message
- On connections the send data immediately, this was never noticed
as the FINISHED in rustls buffers was send with the app data
- On passive FTP connections, curl does not send any data after
the handshake, leaving FINISHED unsent and the server never
responded as it was waiting on this.

Closes #13686

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