Do not default to host/ for client keytabs

When the normal (acceptor) keytab is being used to obtain initial
credentials, it is reasonable to use the default hostbased service
principal (host/fully.qualified.localhost.domain) when no client
principal is given.  This behavior is not very reasonable when
the default client keytab is being used, as host/ credentials are
not normally client credentials.

Make kinit -i match up with the GSS-API behavior when client keytabs
are in use, using the name of the first entry in the keytab when
no name is explicitly given.

ticket: 7892
Test that kinit -k -i picks the intended principal

Prior to ticket 7892 it would use the default host/ principal
when no principal was given on the command line.

ticket: 7892
Remove dead code from the mechglue initialization

The stat check in gss_indicate_mechs had no consequent and would have
been redundant with logic in updateMechList if it did.

[ghudson@mit.edu: elaborated commit message; removed unused
g_mechSetTime and now-irrelevant comment]
Load mechglue config files from /etc/gss/mech.d

In addition to loading /etc/gss/mech, glob for *.conf files in
/etc/gss/mech.d.  Load only config files which have changed since the
highest mtime we saw in the previous scan.  Scan at most once per
second to avoid excessive numbers of filesystem syscalls for busy
GSSAPI applications.

[ghudson@mit.edu: rewrote commit message; style changes; added
once-per-second throttle on glob/stat calls]

ticket: 7882 (new)
Document /etc/gss/mech.d/*.conf

[ghudson@mit.edu: editorial changes]
Fix fencepost error in krad timeout handler

ticket: 7911
target_version: 1.12.2
tags: pullup
Improve pointer hygiene around gss_display_name

GSSAPI functions are responsible for setting their output parameters
on failure.  Take greater care to do so in krb5_gss_display_name.

The mechglue is generally defensive about initializing variables used
as outputs, and not assuming that mechs will set them on failure.
Make gssint_convert_name_to_union_name initialize
union_name->external_name before calling mech->gss_display_name, so
that if the mech's gss_display_name doesn't touch it, we don't free an
uninitialized pointer.

Either one of these changes prevents an unlikely memory bug which
could occur if krb5_gss_init_context fails within
krb5_gss_display_name when called from
gssint_convert_name_to_union_name.

ticket: 7915 (new)
target_version: 1.12.2
Don't blindly use PKCS11 slot IDs in PKINIT

Passing invalid slot IDs to C_OpenSession can cause some PKCS #11
implementations (such as the Solaris one) to crash.  If a PKINIT
identity specifies a slotid, use it to filter the result of
C_GetSlotList, but don't try it if it does not appear in the list.

ticket: 7916
target_version: 1.12.2
tags: pullup
Properly handle PKCS11 label in PKINIT

The CK_TOKEN_INFO label field is defined to be zero-filled, but it may
not be zero-terminated if all bytes of the field are used.  Use only
length-counted operations to process it.  Also avoid underrunning the
buffer pointer if the label is empty or contains only whitespace.

ticket: 7917
target_version: 1.12.2
tags: pullup
Fix uninitialized variable bug in KEYRING ccache

Commit 5f4a4d7d357fedac5feadc65c09ecf487ff98db8 removed the only
unconditional assignment of ret in get_time_offsets, causing the
function to return an uninitialized value if nothing goes wrong.
Initialize ret at declaration time to fix this.
Make tcl_kadm5.c work with Tcl 8.6

Directly accessing the result field of Tcl_Interp has been deprecated
for a long time, requires a special define in Tcl 8.6, and will be
impossible in Tcl 9.  Use Tcl_SetResult instead.  The new error
messages are less helpful than the old ones, but this is just support
infrastructure for old tests, so it isn't important.

ticket: 7924
Simplify sendto_kdc.c

* Get rid of the "x" member of conn_state, which used to be a union
  but hasn't been since r14742.
* Define a structure type for the "out" member of conn_state.
* Rename incoming_krb5_message to incoming_message for brevity.
* Make the "pos" member of incoming_message an offset instead of a
  pointer, simplifying several present and future computations.
* Use "in" and "out" aliases to the conn_state in and out members
  where it improves brevity.
* Rename set_conn_state_msg_length to set_transport_message and give
  it a descriptive comment.
* Call set_transport_message from start_connection only, instead of
  once in add_connection and perhaps again in start_connection.  To
  make this possible, pass the original message argument to maybe_send
  and start_connection.
* Use make_data and empty_data helpers where appropriate.
Add helper to determine if a KDC is the master

Add a new function k5_kdc_is_master in locate_kdc.c to determine
whether a KDC matches one of the masters, and use it in
krb5_sendto_kdc.
Use k5_transport(_strategy) enums for k5_sendto

In k5_sendto and k5_locate_server, replace "socktype" parameters with
a new enumerator k5_transport, so that we can add new transports which
are not in the socket type namespace.  Control the order in which we
make connections of different types using a new k5_transport_strategy
enumerator, to simplify the logic for adding new transports later.
Control the result of k5_locate_server with a no_udp boolean rather
than a socket type.

[ghudson@mit.edu: renamed type to k5_transport; k5_locate_server
 no_udp change; clarified commit message]
[kaduk@mit.edu: name variables of type k5_transport 'transport']
[nalin@redhat.com: use transport rather than sock_type in more places,
 add and use k5_transport_strategy, update the test program]
Build support for TLS used by HTTPS proxy support

Add a --with-proxy-tls-impl option to configure, taking 'openssl',
'auto', or invocation as --without-proxy-tls-impl.  Use related CFLAGS
when building lib/krb5/os, and LIBS when linking libkrb5.  Call the
OpenSSL library startup functions during library initialization.
Add ASN.1 codec for KKDCP's KDC-PROXY-MESSAGE

Handle encoding and decoding [MS-KKDCP] proxy messages, including
handling of the additional length bytes.  Early versions of [MS-KKDCP]
incorrectly omit that the size of the proxied message is prepended to
the proxied message, as it is when we're using plain TCP, before
encoding the proxy-message structure.  This is fixed at least as of
version 2.1 of the spec.

[nalin@redhat.com: add tests]
Dispatch-style protocol switching for transport

Switch to using per-transport-type functions when a socket that we're
using to communicate with a server becomes readable or writable, and add
them as pointers to the connection state.  The functions are passed the
name of the realm of the server being contacted, as we expect to need
this in the near future.

[nalin@redhat.com: replace macros with typedefs]
[nalin@redhat.com: compare transports with TCP_OR_UDP rather than with 0]
HTTPS transport (Microsoft KKDCPP implementation)

Add an 'HTTPS' transport type which connects to an [MS-KKDCP] proxy
server using HTTPS to communicate with a KDC.  The KDC's name should
take the form of an HTTPS URL (e.g. "https://proxybox/KdcProxy").

An HTTPS connection's encryption layer can be reading and writing when
the application layer is expecting to write and read, so the HTTPS
callbacks have to handle being called multiple times.

[nalin@redhat.com: use cleanup labels, make sure we always send the
 realm name, keep a copy of the URI on-hand, move most of the
 conditionally-compiled sections into their own conditionally-built
 functions, break out HTTPS request formatting into a helper function,
 handle the MS-KKDCP length bytes, update comments to mention specific
 versions of the MS-KKDCP spec, differentiate TCP and HTTP trace
 messages, trace unparseable responses]
Load custom anchors when using KKDCP

Add an http_anchors per-realm setting which we'll apply when using an
HTTPS proxy, more or less mimicking the syntax of its similarly-named
PKINIT counterpart.  We only check the [realms] section, though.
Check names in the server's cert when using KKDCP

When we connect to a KDC using an HTTPS proxy, check that the naming
information in the certificate matches the name or address which we
extracted from the server URL in the configuration.