We shouldn't allow both "-tls1" and "-tls1_2", or "-tls1" and "-no_tls1_2".
The only time multiple flags are allowed is where they are all "-no_<prot>".
This fixes Github Issue #1268
Reviewed-by: Rich Salz <rsalz@openssl.org>
Don't use BN_hex2bn() for PSK key conversion as the conversion to
BN and back removes leading zeroes, use OPENSSL_hexstr2buf() instead.
RT#4554
Reviewed-by: Matt Caswell <matt@openssl.org>
On Windows we were using the function _kbhit() to determine whether there
was input waiting in stdin for us to read. Actually all this does is work
out whether there is a keyboard press event waiting to be processed in the
input buffer. This only seems to work in a standard Windows console (not
Msys console) and also doesn't work if you redirect the input from some
other source (as we do in TLSProxy tests). This commit changes things to
work differently depending on whether we are on the Windows console or not.
RT#4255
Reviewed-by: Richard Levitte <levitte@openssl.org>
In s_server we call BIO_sock_should_retry() to determine the state of the
socket and work out whether we should retry an operation on it or not.
However if you leave it too long to call this then other operations may
have occurred in the meantime which affect the result. Therefore we should
call it early and remember the result for when we need to use it. This fixes
a test problem on Windows.
Another issue with s_server on Windows is that some of output to stdout does
not get displayed immediately. Apparently more liberal use of BIO_flush is
required.
RT#4255
Reviewed-by: Richard Levitte <levitte@openssl.org>
Discard useless static engine_id
Add a const qualifier
Fix some spelling
Reviewed-by: Richard Levitte <levitte@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
If the application has limited the size of the async pool using
ASYNC_init_thread() then we could run out of jobs while trying to start a
libssl io operation. However libssl was failing to handle this and treating
it like a fatal error. It should not be fatal...we just need to retry when
there are jobs available again.
Reviewed-by: Richard Levitte <levitte@openssl.org>
Building with -DCHARSET_EBCDIC and using --strict-warnings resulted in
lots of miscellaneous errors. This fixes it.
Reviewed-by: Andy Polyakov <appro@openssl.org>
Make X509_OBJECT, X509_STORE_CTX, X509_STORE, X509_LOOKUP,
and X509_LOOKUP_METHOD opaque.
Remove unused X509_CERT_FILE_CTX
Reviewed-by: Richard Levitte <levitte@openssl.org>
Reviewed-by: Dr. Stephen Henson <steve@openssl.org>
BIO_new, etc., don't need a non-const BIO_METHOD. This allows all the
built-in method tables to live in .rodata.
Reviewed-by: Richard Levitte <levitte@openssl.org>
* Perform ALPN after the SNI callback; the SSL_CTX may change due to
that processing
* Add flags to indicate that we actually sent ALPN, to properly error
out if unexpectedly received.
* clean up ssl3_free() no need to explicitly clear when doing memset
* document ALPN functions
Signed-off-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Emilia Käsper <emilia@openssl.org>
Previously s_client and s_server relied on using SSL_pending() which does
not take into account read_ahead. For read pipelining to work, read_ahead
gets set automatically. Therefore s_client and s_server have been
converted to use SSL_has_pending() instead.
Reviewed-by: Tim Hudson <tjh@openssl.org>
This capability is required for read pipelining. We will only read in as
many records as will fit in the read buffer (and the network can provide
in one go). The bigger the buffer the more records we can process in
parallel.
Reviewed-by: Tim Hudson <tjh@openssl.org>
Add the options min_send_frag and max_pipelines to s_server and s_client
in order to control pipelining capabilities. This will only have an effect
if a pipeline capable cipher is used (such as the one provided by the
dasync engine).
Reviewed-by: Tim Hudson <tjh@openssl.org>
in s_server cmd:
specifying -trace option, falls through and turn-on security_debug
Signed-off-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
- srtp_profiles variable is defined when building with SRTP, keeping
the variable usage also under ifndef OPENSSL_NO_SRTP
- alpn help option was kept under ifndef OPENSSL_NO_SRTP
Reviewed-by: Kurt Roeckx <kurt@openssl.org>
Reviewed-by: Rich Salz <rsalz@openssl.org>
The SRP user database lookup method SRP_VBASE_get_by_user had confusing
memory management semantics; the returned pointer was sometimes newly
allocated, and sometimes owned by the callee. The calling code has no
way of distinguishing these two cases.
Specifically, SRP servers that configure a secret seed to hide valid
login information are vulnerable to a memory leak: an attacker
connecting with an invalid username can cause a memory leak of around
300 bytes per connection.
Servers that do not configure SRP, or configure SRP but do not configure
a seed are not vulnerable.
In Apache, the seed directive is known as SSLSRPUnknownUserSeed.
To mitigate the memory leak, the seed handling in SRP_VBASE_get_by_user
is now disabled even if the user has configured a seed.
Applications are advised to migrate to SRP_VBASE_get1_by_user. However,
note that OpenSSL makes no strong guarantees about the
indistinguishability of valid and invalid logins. In particular,
computations are currently not carried out in constant time.
Reviewed-by: Rich Salz <rsalz@openssl.org>
On some platforms, the implementation is such that a signed char
triggers a warning when used with is*() functions. On others, the
behavior is outright buggy when presented with a char that happens
to get promoted to a negative integer.
The safest thing is to cast the char that's used to an unsigned char.
Reviewed-by: Andy Polyakov <appro@openssl.org>
* added missing help option messages
* ecdh_single option is removed as it is a no-op and not an option
supported in earlier versions
* ssl_ctx_security_debug() was invoked before ctx check for NULL
* trusted_first option can be removed, as it is always enabled in 1.1.
But not removed the option, require confirmation.
Signed-off-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
The DTLSv1_listen function exposed details of the underlying BIO
abstraction and did not properly allow for IPv6. This commit changes the
"peer" argument to be a BIO_ADDR and makes it a first class function
(rather than a ctrl) to ensure proper type checking.
Reviewed-by: Richard Levitte <levitte@openssl.org>
s_socket.c gets brutally cleaned out and now consists of only two
functions, one for client and the other for server. They both handle
AF_INET, AF_INET6 and additionally AF_UNIX where supported. The rest
is just easy adaptation.
Both s_client and s_server get the new flags -4 and -6 to force the
use of IPv4 or IPv6 only.
Also, the default host "localhost" in s_client is removed. It's not
certain that this host is set up for both IPv4 and IPv6. For example,
Debian has "ip6-localhost" as the default hostname for [::1]. The
better way is to default |host| to NULL and rely on BIO_lookup() to
return a BIO_ADDRINFO with the appropriate loopback address for IPv4
or IPv6 as indicated by the |family| parameter.
Reviewed-by: Kurt Roeckx <kurt@openssl.org>
The control commands that previously took a struct sockaddr * have
been changed to take a BIO_ADDR * instead.
Reviewed-by: Kurt Roeckx <kurt@openssl.org>
PACKET contents should be read-only. To achieve this, also
- constify two user callbacks
- constify BUF_reverse.
Reviewed-by: Rich Salz <rsalz@openssl.org>
Some users want to disable SSL 3.0/TLS 1.0/TLS 1.1, and enable just
TLS 1.2. In the future they might want to disable TLS 1.2 and
enable just TLS 1.3, ...
This commit makes it possible to disable any or all of the TLS or
DTLS protocols. It also considerably simplifies the SSL/TLS tests,
by auto-generating the min/max version tests based on the set of
supported protocols (425 explicitly written out tests got replaced
by two loops that generate all 425 tests if all protocols are
enabled, fewer otherwise).
Reviewed-by: Richard Levitte <levitte@openssl.org>
It turns out that -pause calls the undocumented function SSL_set_debug.
That just sets flag inside the SSL structure. That flag, despite
the command is never used. So remove the flag, the field, and the
function.
Reviewed-by: Richard Levitte <levitte@openssl.org>
Rename BUF_{strdup,strlcat,strlcpy,memdup,strndup,strnlen}
to OPENSSL_{strdup,strlcat,strlcpy,memdup,strndup,strnlen}
Add #define's for the old names.
Add CRYPTO_{memdup,strndup}, called by OPENSSL_{memdup,strndup} macros.
Reviewed-by: Tim Hudson <tjh@openssl.org>
s_server was trying to set the ECDH curve when no-ec was defined. This also
highlighted the fact that the -no_ecdhe option to s_server is broken, and
doesn't make any sense any more (ECDHE is on by default and the only way it
can be disabled is through the cipherstring). Therefore this commit removes
the option.
Reviewed-by: Kurt Roeckx <kurt@openssl.org>
In theory the pthreads approach for Thread Local Storage should be more
portable.
This also changes some APIs in order to accommodate this change. In
particular ASYNC_init_pool is renamed ASYNC_init_thread and
ASYNC_free_pool is renamed ASYNC_cleanup_thread. Also introduced ASYNC_init
and ASYNC_cleanup.
Reviewed-by: Rich Salz <rsalz@openssl.org>
If an async event occurs during a renegotiation in SSL_read then s_server
was looping around, detecting we were in init and calling
init_ssl_connection instead of re-calling SSL_read.
Reviewed-by: Rich Salz <rsalz@openssl.org>
Initial API implemented for notifying applications that an ASYNC_JOB
has completed. Currently only s_server is using this. The Dummy Async
engine "cheats" in that it notifies that it has completed *before* it
pauses the job. A normal async engine would not do that.
Only the posix version of this has been implemented so far, so it will
probably fail to compile on Windows at the moment.
Reviewed-by: Rich Salz <rsalz@openssl.org>
It is expensive to create the ASYNC_JOB objects due to the "makecontext"
call. This change adds support for pools of ASYNC_JOB objects so that we
don't have to create a new ASYNC_JOB every time we want to use one.
Reviewed-by: Rich Salz <rsalz@openssl.org>
The s_server option -WWW was not async aware, and therefore was not
handling SSL_ERROR_WANT_ASYNC conditions. This commit fixes that.
Reviewed-by: Rich Salz <rsalz@openssl.org>
A new -async option is added which activates SSL_MODE_ASYNC. Also
SSL_WANT_ASYNC errors are handled appropriately.
Reviewed-by: Rich Salz <rsalz@openssl.org>
SSL_state has been replaced by SSL_get_state and SSL_set_state is no longer
supported.
Reviewed-by: Tim Hudson <tjh@openssl.org>
Reviewed-by: Richard Levitte <levitte@openssl.org>
s_server was (ab)using SSL_set_state to force a renegotiation. This is a
bad way to do things and does not work with the new state machine code, so
we need to do it a different way.
Reviewed-by: Tim Hudson <tjh@openssl.org>
Reviewed-by: Richard Levitte <levitte@openssl.org>
Clean up and remove lots of code that is now no longer needed due to the
move to the new state machine.
Reviewed-by: Tim Hudson <tjh@openssl.org>
Reviewed-by: Richard Levitte <levitte@openssl.org>
Loading the config file after processing command line options can
cause problems, e.g. where an engine provides new ciphers/digests
these are not then recoginised on the command line. Move the
default config file loading to before the command line option
processing. Whilst we're doing this we might as well centralise
this instead of doing it individually for each application. Finally
if we do it before the OpenSSL_add_ssl_algorithms() call then
ciphersuites provided by an engine (e.g. GOST) can be available to
the apps.
RT#4085
RT#4086
Reviewed-by: Richard Levitte <levitte@openssl.org>
For those command line options that take the verification options
-CApath and -CAfile, if those options are absent then the default path or
file is used instead. It is not currently possible to specify *no* path or
file at all. This change adds the options -no-CApath and -no-CAfile to
specify that the default locations should not be used to all relevant
applications.
Reviewed-by: Andy Polyakov <appro@openssl.org>
Use sockaddr_storage not sockaddr for the client IP address to allow for
IPv6.
Also fixed a section of code which was conditional on OPENSSL_NO_DTLS1
which should not have been.
Reviewed-by: Andy Polyakov <appro@openssl.org>
DTLSv1_listen is a commonly used function within DTLS solutions for
listening for new incoming connections. This commit adds support to s_server
for using it.
Reviewed-by: Andy Polyakov <appro@openssl.org>
If the output to stdout or the input from stdin is meant to be binary,
it's deeply unsetting to get the occasional LF converted to CRLF or
the other way around. If someone happens to forget to redirect stdin
or stdout, they will get gibberish anyway, line ending conversion will
not change that.
Therefore, let's not have dup_bio_* decide unilaterally what mode the
BIO derived from stdin and stdout, and rather let the app decide by
declaring the intended format.
Reviewed-by: Tim Hudson <tjh@openssl.org>
The -use_srtp s_client/s_server option is supposed to take a colon
separated string as an argument. In master this was incorrectly set to
expect a filename.
Reviewed-by: Rich Salz <rsalz@openssl.org>
When generating a private key, try to make the output file be readable
only by the owner. Put it in CHANGES file since it might be noticeable.
Add "int private" flag to apps that write private keys, and check that it's
set whenever we do write a private key. Checked via assert so that this
bug (security-related) gets fixed. Thanks to Viktor for help in tracing
the code-paths where private keys are written.
Reviewed-by: Viktor Dukhovni <viktor@openssl.org>
This is a workaround so old that nobody remembers what buggy clients
it was for. It's also been broken in stable branches for two years and
nobody noticed (see
https://boringssl-review.googlesource.com/#/c/1694/).
Reviewed-by: Tim Hudson <tjh@openssl.org>
Here are the "rules" for handling flags that depend on #ifdef:
- Do not ifdef the enum. Only ifdef the OPTIONS table. All ifdef'd
entries appear at the end; by convention "engine" is last. This
ensures that at run-time, the flag will never be recognized/allowed.
The next two bullets entries are for silencing compiler warnings:
- In the while/switch parsing statement, use #ifdef for the body to
disable it; leave the "case OPT_xxx:" and "break" statements outside
the ifdef/ifndef. See ciphers.c for example.
- If there are multiple options controlled by a single guard, OPT_FOO,
OPT_BAR, etc., put a an #ifdef around the set, and then do "#else"
and a series of case labels and a break. See OPENSSL_NO_AES in cms.c
for example.
Reviewed-by: Matt Caswell <matt@openssl.org>
The module loading feature got broken a while ago, so restore it, but
have it a bit more explicit this time around.
Reviewed-by: Stephen Henson <steve@openssl.org>
Given the pervasive nature of TLS extensions it is inadvisable to run
OpenSSL without support for them. It also means that maintaining
the OPENSSL_NO_TLSEXT option within the code is very invasive (and probably
not well tested). Therefore it is being removed.
Reviewed-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Richard Levitte <levitte@openssl.org>
This commit changes the way that we do server side protocol version
negotiation. Previously we had a whole set of code that had an "up front"
state machine dedicated to the negotiating the protocol version. This adds
significant complexity to the state machine. Historically the justification
for doing this was the support of SSLv2 which works quite differently to
SSLv3+. However, we have now removed support for SSLv2 so there is little
reason to maintain this complexity.
The one slight difficulty is that, although we no longer support SSLv2, we
do still support an SSLv3+ ClientHello in an SSLv2 backward compatible
ClientHello format. This is generally only used by legacy clients. This
commit adds support within the SSLv3 code for these legacy format
ClientHellos.
Server side version negotiation now works in much the same was as DTLS,
i.e. we introduce the concept of TLS_ANY_VERSION. If s->version is set to
that then when a ClientHello is received it will work out the most
appropriate version to respond with. Also, SSLv23_method and
SSLv23_server_method have been replaced with TLS_method and
TLS_server_method respectively. The old SSLv23* names still exist as
macros pointing at the new name, although they are deprecated.
Subsequent commits will look at client side version negotiation, as well of
removal of the old s23* code.
Reviewed-by: Kurt Roeckx <kurt@openssl.org>
Follow the same convention the other OPENSSL_NO_xxx header files
do, and use #error instead of making the header file be a no-op.
Reviewed-by: Matt Caswell <matt@openssl.org>
Remove Kerberos related options from the apps to prepare for the
subsequent commits which will remove libcrypto and libssl support for
Kerberos.
Reviewed-by: Rich Salz <rsalz@openssl.org>
For the various string-compare routines (strcmp, strcasecmp, str.*cmp)
use "strcmp()==0" instead of "!strcmp()"
Reviewed-by: Tim Hudson <tjh@openssl.org>
Compiling OpenSSL code with MSVC and /W4 results in a number of warnings.
One category of warnings is particularly interesting - C4701 (potentially
uninitialized local variable 'name' used). This warning pretty much means
that there's a code path which results in uninitialized variables being used
or returned. Depending on compiler, its options, OS, values in registers
and/or stack, the results can be nondeterministic. Cases like this are very
hard to debug so it's rational to fix these issues.
This patch contains a set of trivial fixes for all the C4701 warnings (just
initializing variables to 0 or NULL or appropriate error code) to make sure
that deterministic values will be returned from all the execution paths.
RT#3835
Signed-off-by: Matt Caswell <matt@openssl.org>
Matt's note: All of these appear to be bogus warnings, i.e. there isn't
actually a code path where an unitialised variable could be used - its just
that the compiler hasn't been able to figure that out from the logic. So
this commit is just about silencing spurious warnings.
Reviewed-by: Rich Salz <rsalz@openssl.org>
For a local variable:
TYPE *p;
Allocations like this are "risky":
p = OPENSSL_malloc(sizeof(TYPE));
if the type of p changes, and the malloc call isn't updated, you
could get memory corruption. Instead do this:
p = OPENSSL_malloc(sizeof(*p));
Also fixed a few memset() calls that I noticed while doing this.
Reviewed-by: Richard Levitte <levitte@openssl.org>
After the finale, the "real" final part. :) Do a recursive grep with
"-B1 -w [a-zA-Z0-9_]*_free" to see if any of the preceeding lines are
an "if NULL" check that can be removed.
Reviewed-by: Tim Hudson <tjh@openssl.org>
This gets BN_.*free:
BN_BLINDING_free BN_CTX_free BN_FLG_FREE BN_GENCB_free
BN_MONT_CTX_free BN_RECP_CTX_free BN_clear_free BN_free BUF_MEM_free
Also fix a call to DSA_SIG_free to ccgost engine and remove some #ifdef'd
dead code in engines/e_ubsec.
Reviewed-by: Richard Levitte <levitte@openssl.org>
Add OPENSSL_clear_free which merges cleanse and free.
(Names was picked to be similar to BN_clear_free, etc.)
Removed OPENSSL_freeFunc macro.
Fixed the small simple ones that are left:
CRYPTO_free CRYPTO_free_locked OPENSSL_free_locked
Reviewed-by: Richard Levitte <levitte@openssl.org>
No point in proceeding if you're out of memory. So change
*all* OPENSSL_malloc calls in apps to use the new routine which
prints a message and exits.
Reviewed-by: Richard Levitte <levitte@openssl.org>
Don't check for NULL before calling a free routine. This gets X509_.*free:
x509_name_ex_free X509_policy_tree_free X509_VERIFY_PARAM_free
X509_STORE_free X509_STORE_CTX_free X509_PKEY_free
X509_OBJECT_free_contents X509_LOOKUP_free X509_INFO_free
Reviewed-by: Richard Levitte <levitte@openssl.org>
Many functions had a BIO* parameter, and it was always called
with bio_err. Remove the param and just use bio_err.
Reviewed-by: Matt Caswell <matt@openssl.org>
Make setup_engine be a dummy if NO_ENGINE is enabled.
The option is not enabled if NO_ENGINE is enabled, so the one "wasted"
variable just sits there. Removes some variables and code.
Reviewed-by: Richard Levitte <levitte@openssl.org>
This is merges the old "rsalz-monolith" branch over to master. The biggest
change is that option parsing switch from cascasding 'else if strcmp("-foo")'
to a utility routine and somethin akin to getopt. Also, an error in the
command line no longer prints the full summary; use -help (or --help :)
for that. There have been many other changes and code-cleanup, see
bullet list below.
Special thanks to Matt for the long and detailed code review.
TEMPORARY:
For now, comment out CRYPTO_mem_leaks() at end of main
Tickets closed:
RT3515: Use 3DES in pkcs12 if built with no-rc2
RT1766: s_client -reconnect and -starttls broke
RT2932: Catch write errors
RT2604: port should be 'unsigned short'
RT2983: total_bytes undeclared #ifdef RENEG
RT1523: Add -nocert to fix output in x509 app
RT3508: Remove unused variable introduced by b09eb24
RT3511: doc fix; req default serial is random
RT1325,2973: Add more extensions to c_rehash
RT2119,3407: Updated to dgst.pod
RT2379: Additional typo fix
RT2693: Extra include of string.h
RT2880: HFS is case-insensitive filenames
RT3246: req command prints version number wrong
Other changes; incompatibilities marked with *:
Add SCSV support
Add -misalign to speed command
Make dhparam, dsaparam, ecparam, x509 output C in proper style
Make some internal ocsp.c functions void
Only display cert usages with -help in verify
Use global bio_err, remove "BIO*err" parameter from functions
For filenames, - always means stdin (or stdout as appropriate)
Add aliases for -des/aes "wrap" ciphers.
*Remove support for IISSGC (server gated crypto)
*The undocumented OCSP -header flag is now "-header name=value"
*Documented the OCSP -header flag
Reviewed-by: Matt Caswell <matt@openssl.org>
EVP_.*free; this gets:
EVP_CIPHER_CTX_free EVP_PKEY_CTX_free EVP_PKEY_asn1_free
EVP_PKEY_asn1_set_free EVP_PKEY_free EVP_PKEY_free_it
EVP_PKEY_meth_free; and also EVP_CIPHER_CTX_cleanup
Reviewed-by: Kurt Roeckx <kurt@openssl.org>
Start ensuring all OpenSSL "free" routines allow NULL, and remove
any if check before calling them.
This gets DH_free, DSA_free, RSA_free
Reviewed-by: Matt Caswell <matt@openssl.org>
Ensure that all libssl functions called from within the apps have their
return values checked where appropriate.
Reviewed-by: Richard Levitte <levitte@openssl.org>
Some miscellaneous removal of dead code from apps. Also fix an issue with
error handling with pkcs7.
Reviewed-by: Richard Levitte <levitte@openssl.org>
Miscellaneous unchecked malloc fixes. Also fixed some mem leaks on error
paths as I spotted them along the way.
Reviewed-by: Tim Hudson <tjh@openssl.org>
X509_V_FLAG_NO_ALT_CHAINS flag. Using this option means that when building
certificate chains, the first chain found will be the one used. Without this
flag, if the first chain found is not trusted then we will keep looking to
see if we can build an alternative chain instead.
Reviewed-by: Dr. Stephen Henson <steve@openssl.org>
An expired IETF Internet-Draft (seven years old) that nobody
implements, and probably just as good as NSA DRBG work.
Reviewed-by: Richard Levitte <levitte@openssl.org>
Rename OPENSSL_SYSNAME_xxx to OPENSSL_SYS_xxx
Remove MS_STATIC; it's a relic from platforms <32 bits.
Reviewed-by: Andy Polyakov <appro@openssl.org>
Reviewed-by: Tim Hudson <tjh@openssl.org>
and UDP header) when setting an mtu. This constant is not always correct (e.g.
if using IPv6). Use the new DTLS_CTRL functions instead.
Reviewed-by: Tim Hudson <tjh@openssl.org>
When no-ssl3 is set only make SSLv3 disabled by default. Retain -ssl3
options for s_client/s_server/ssltest.
When no-ssl3-method is set SSLv3_*method() is removed and all -ssl3
options.
We should document this somewhere, e.g. wiki, FAQ or manual page.
Reviewed-by: Emilia Käsper <emilia@openssl.org>
The "-unix <path>" argument allows s_server and s_client to use a unix
domain socket in the filesystem instead of IPv4 ("-connect", "-port",
"-accept", etc). If s_server exits gracefully, such as when "-naccept"
is used and the requested number of SSL/TLS connections have occurred,
then the domain socket file is removed. On ctrl-C, it is likely that
the stale socket file will be left over, such that s_server would
normally fail to restart with the same arguments. For this reason,
s_server also supports an "-unlink" option, which will clean up any
stale socket file before starting.
If you have any reason to want encrypted IPC within an O/S instance,
this concept might come in handy. Otherwise it just demonstrates that
there is nothing about SSL/TLS that limits it to TCP/IP in any way.
(There might also be benchmarking and profiling use in this path, as
unix domain sockets are much lower overhead than connecting over local
IP addresses).
Signed-off-by: Geoff Thorpe <geoff@openssl.org>
Add auto DH parameter support. This is roughly equivalent to the
ECDH auto curve selection but for DH. An application can just call
SSL_CTX_set_auto_dh(ctx, 1);
and appropriate DH parameters will be used based on the size of the
server key.
Unlike ECDH there is no way a peer can indicate the range of DH parameters
it supports. Some peers cannot handle DH keys larger that 1024 bits for
example. In this case if you call:
SSL_CTX_set_auto_dh(ctx, 2);
Only 1024 bit DH parameters will be used.
If the server key is 7680 bits or more in size then 8192 bit DH parameters
will be used: these will be *very* slow.
The old export ciphersuites aren't supported but those are very
insecure anyway.
