Net::SSLeay(3pm) User Contributed Perl Documentation Net::SSLeay(3pm)NAMENet::SSLeay - Perl extension for using OpenSSL
SYNOPSIS
use Net::SSLeay qw(get_https post_https sslcat make_headers make_form);
($page) = get_https('www.bacus.pt', 443, '/'); # 1
($page, $response, %reply_headers)
= get_https('www.bacus.pt', 443, '/', # 2
make_headers(User-Agent => 'Cryptozilla/5.0b1',
Referer => 'https://www.bacus.pt'
));
($page, $result, %headers) = # 2b
= get_https('www.bacus.pt', 443, '/protected.html',
make_headers(Authorization =>
'Basic ' . MIME::Base64::encode("$user:$pass",''))
);
($page, $response, %reply_headers)
= post_https('www.bacus.pt', 443, '/foo.cgi', '', # 3
make_form(OK => '1',
name => 'Sampo'
));
$reply = sslcat($host, $port, $request); # 4
($reply, $err, $server_cert) = sslcat($host, $port, $request); # 5
$Net::SSLeay::trace = 2; # 0=no debugging, 1=ciphers, 2=trace, 3=dump data
DESCRIPTION
There is a related module called "Net::SSLeay::Handle" included in this
distribution that you might want to use instead. It has its own pod
documentation.
This module offers some high level convenience functions for accessing
web pages on SSL servers (for symmetry, the same API is offered for
accessing http servers, too), an "sslcat()" function for writing your
own clients, and finally access to the SSL api of the SSLeay/OpenSSL
package so you can write servers or clients for more complicated
applications.
For high level functions it is most convenient to import them into your
main namespace as indicated in the synopsis.
Case 1 demonstrates the typical invocation of get_https() to fetch an
HTML page from secure server. The first argument provides the hostname
or IP in dotted decimal notation of the remote server to contact. The
second argument is the TCP port at the remote end (your own port is
picked arbitrarily from high numbered ports as usual for TCP). The
third argument is the URL of the page without the host name part. If in
doubt consult the HTTP specifications at <http://www.w3c.org>.
Case 2 demonstrates full fledged use of "get_https()". As can be seen,
"get_https()" parses the response and response headers and returns them
as a list, which can be captured in a hash for later reference. Also a
fourth argument to "get_https()" is used to insert some additional
headers in the request. "make_headers()" is a function that will
convert a list or hash to such headers. By default "get_https()"
supplies "Host" (to make virtual hosting easy) and "Accept" (reportedly
needed by IIS) headers.
Case 2b demonstrates how to get a password protected page. Refer to the
HTTP protocol specifications for further details (e.g. RFC-2617).
Case 3 invokes "post_https()" to submit a HTML/CGI form to a secure
server. The first four arguments are equal to "get_https()" (note that
the empty string ('') is passed as header argument). The fifth
argument is the contents of the form formatted according to CGI
specification. In this case the helper function "make_https()" is used
to do the formatting, but you could pass any string. "post_https()"
automatically adds "Content-Type" and "Content-Length" headers to the
request.
Case 4 shows the fundamental "sslcat()" function (inspired in spirit by
the "netcat" utility :-). It's your swiss army knife that allows you to
easily contact servers, send some data, and then get the response. You
are responsible for formatting the data and parsing the response -
"sslcat()" is just a transport.
Case 5 is a full invocation of "sslcat()" which allows the return of
errors as well as the server (peer) certificate.
The $trace global variable can be used to control the verbosity of the
high level functions. Level 0 guarantees silence, level 1 (the default)
only emits error messages.
Alternate versions of the API
The above mentioned functions actually return the response headers as a
list, which only gets converted to hash upon assignment (this
assignment looses information if the same header occurs twice, as may
be the case with cookies). There are also other variants of the
functions that return unprocessed headers and that return a reference
to a hash.
($page, $response, @headers) = get_https('www.bacus.pt', 443, '/');
for ($i = 0; $i < $#headers; $i+=2) {
print "$headers[$i] = " . $headers[$i+1] . "\n";
}
($page, $response, $headers, $server_cert)
= get_https3('www.bacus.pt', 443, '/');
print "$headers\n";
($page, $response, %headers_ref, $server_cert)
= get_https4('www.bacus.pt', 443, '/');
for $k (sort keys %{headers_ref}) {
for $v (@{$headers_ref{$k}}) {
print "$k = $v\n";
}
}
All of the above code fragments accomplish the same thing: display all
values of all headers. The API functions ending in "3" return the
headers simply as a scalar string and it is up to the application to
split them up. The functions ending in "4" return a reference to a hash
of arrays (see perlref and perllol if you are not familiar with complex
perl data structures). To access a single value of such a header hash
you would do something like
print $headers_ref{COOKIE}[0];
Variants 3 and 4 also allow you to discover the server certificate in
case you would like to store or display it, e.g.
($p, $resp, $hdrs, $server_cert) = get_https3('www.bacus.pt', 443, '/');
if (!defined($server_cert) || ($server_cert == 0)) {
warn "Subject Name: undefined, Issuer Name: undefined";
} else {
warn 'Subject Name: '
. Net::SSLeay::X509_NAME_oneline(
Net::SSLeay::X509_get_subject_name($server_cert))
. 'Issuer Name: '
. Net::SSLeay::X509_NAME_oneline(
Net::SSLeay::X509_get_issuer_name($server_cert));
}
Beware that this method only allows after the fact verification of the
certificate: by the time "get_https3()" has returned the https request
has already been sent to the server, whether you decide to trust it or
not. To do the verification correctly you must either employ the
OpenSSL certificate verification framework or use the lower level API
to first connect and verify the certificate and only then send the http
data. See the implementation of "ds_https3()" for guidance on how to do
this.
Using client certificates
Secure web communications are encrypted using symmetric crypto keys
exchanged using encryption based on the certificate of the server.
Therefore in all SSL connections the server must have a certificate.
This serves both to authenticate the server to the clients and to
perform the key exchange.
Sometimes it is necessary to authenticate the client as well. Two
options are available: HTTP basic authentication and a client side
certificate. The basic authentication over HTTPS is actually quite safe
because HTTPS guarantees that the password will not travel in the
clear. Never-the-less, problems like easily guessable passwords remain.
The client certificate method involves authentication of the client at
the SSL level using a certificate. For this to work, both the client
and the server have certificates (which typically are different) and
private keys.
The API functions outlined above accept additional arguments that allow
one to supply the client side certificate and key files. The format of
these files is the same as used for server certificates and the caveat
about encrypting private keys applies.
($page, $result, %headers) = # 2c
= get_https('www.bacus.pt', 443, '/protected.html',
make_headers(Authorization =>
'Basic ' . MIME::Base64::encode("$user:$pass",'')),
'', $mime_type6, $path_to_crt7, $path_to_key8);
($page, $response, %reply_headers)
= post_https('www.bacus.pt', 443, '/foo.cgi', # 3b
make_headers('Authorization' =>
'Basic ' . MIME::Base64::encode("$user:$pass",'')),
make_form(OK => '1', name => 'Sampo'),
$mime_type6, $path_to_crt7, $path_to_key8);
Case 2c demonstrates getting a password protected page that also
requires a client certificate, i.e. it is possible to use both
authentication methods simultaneously.
Case 3b is a full blown POST to a secure server that requires both
password authentication and a client certificate, just like in case 2c.
Note: The client will not send a certificate unless the server requests
one. This is typically achieved by setting the verify mode to
"VERIFY_PEER" on the server:
Net::SSLeay::set_verify(ssl, Net::SSLeay::VERIFY_PEER, 0);
See "perldoc ~openssl/doc/ssl/SSL_CTX_set_verify.pod" for a full
description.
Working through a web proxy
"Net::SSLeay" can use a web proxy to make its connections. You need to
first set the proxy host and port using "set_proxy()" and then just use
the normal API functions, e.g:
Net::SSLeay::set_proxy('gateway.myorg.com', 8080);
($page) = get_https('www.bacus.pt', 443, '/');
If your proxy requires authentication, you can supply a username and
password as well
Net::SSLeay::set_proxy('gateway.myorg.com', 8080, 'joe', 'salainen');
($page, $result, %headers) =
= get_https('www.bacus.pt', 443, '/protected.html',
make_headers(Authorization =>
'Basic ' . MIME::Base64::encode("susie:pass",''))
);
This example demonstrates the case where we authenticate to the proxy
as "joe" and to the final web server as "susie". Proxy authentication
requires the "MIME::Base64" module to work.
Certificate verification and Certificate Revoocation Lists (CRLs)
OpenSSL supports the ability to verify peer certificates. It can also
optionally check the peer certificate against a Certificate Revocation
List (CRL) from the certificates issuer. A CRL is a file, created by
the certificate issuer that lists all the certificates that it
previously signed, but which it now revokes. CRLs are in PEM format.
You can enable "Net::SSLeay CRL" checking like this:
&Net::SSLeay::X509_STORE_CTX_set_flags
(&Net::SSLeay::CTX_get_cert_store($ssl),
&Net::SSLeay::X509_V_FLAG_CRL_CHECK);
After setting this flag, if OpenSSL checks a peer's certificate, then
it will attempt to find a CRL for the issuer. It does this by looking
for a specially named file in the search directory specified by
CTX_load_verify_locations. CRL files are named with the hash of the
issuer's subject name, followed by ".r0", ".r1" etc. For example
"ab1331b2.r0", "ab1331b2.r1". It will read all the .r files for the
issuer, and then check for a revocation of the peer cerificate in all
of them. (You can also force it to look in a specific named CRL file.,
see below). You can find out the hash of the issuer subject name in a
CRL with
openssl crl -in crl.pem -hash -noout
If the peer certificate does not pass the revocation list, or if no CRL
is found, then the handshaking fails with an error.
You can also force OpenSSL to look for CRLs in one or more arbitrarily
named files.
my $bio = Net::SSLeay::BIO_new_file($crlfilename, 'r');
my $crl = Net::SSLeay::PEM_read_bio_X509_CRL($bio);
if ($crl) {
Net::SSLeay::X509_STORE_add_crl(Net::SSLeay::CTX_get_cert_store($ssl, $crl);
} else {
error reading CRL....
}
Convenience routines
To be used with Low level API
Net::SSLeay::randomize($rn_seed_file,$additional_seed);
Net::SSLeay::set_cert_and_key($ctx, $cert_path, $key_path);
$cert = Net::SSLeay::dump_peer_certificate($ssl);
Net::SSLeay::ssl_write_all($ssl, $message) or die "ssl write failure";
$got = Net::SSLeay::ssl_read_all($ssl) or die "ssl read failure";
$got = Net::SSLeay::ssl_read_CRLF($ssl [, $max_length]);
$got = Net::SSLeay::ssl_read_until($ssl [, $delimit [, $max_length]]);
Net::SSLeay::ssl_write_CRLF($ssl, $message);
"randomize()" seeds the openssl PRNG with "/dev/urandom" (see the top
of "SSLeay.pm" for how to change or configure this) and optionally with
user provided data. It is very important to properly seed your random
numbers, so do not forget to call this. The high level API functions
automatically call "randomize()" so it is not needed with them. See
also caveats.
"set_cert_and_key()" takes two file names as arguments and sets the
certificate and private key to those. This can be used to set either
cerver certificates or client certificates.
"dump_peer_certificate()" allows you to get a plaintext description of
the certificate the peer (usually the server) presented to us.
"ssl_read_all()" and "ssl_write_all()" provide true blocking semantics
for these operations (see limitation, below, for explanation). These
are much preferred to the low level API equivalents (which implement
BSD blocking semantics). The message argument to "ssl_write_all()" can
be a reference. This is helpful to avoid unnecessary copying when
writing something big, e.g:
$data = 'A' x 1000000000;
Net::SSLeay::ssl_write_all($ssl, \$data) or die "ssl write failed";
"ssl_read_CRLF()" uses "ssl_read_all()" to read in a line terminated
with a carriage return followed by a linefeed (CRLF). The CRLF is
included in the returned scalar.
"ssl_read_until()" uses "ssl_read_all()" to read from the SSL input
stream until it encounters a programmer specified delimiter. If the
delimiter is undefined, $/ is used. If $/ is undefined, "\n" is used.
One can optionally set a maximum length of bytes to read from the SSL
input stream.
"ssl_write_CRLF()" writes $message and appends CRLF to the SSL output
stream.
Low level API
In addition to the high level functions outlined above, this module
contains straight-forward access to SSL part of OpenSSL C api. Only the
SSL subpart of OpenSSL is implemented (if anyone wants to implement
other parts, feel free to submit patches).
See the "ssl.h" header from OpenSSL C distribution for a list of low
level SSLeay functions to call (check SSLeay.xs to see if some function
has been implemented). The module strips the initial "SSL_" off of the
SSLeay names. Generally you should use "Net::SSLeay::" in its place.
For example:
In C:
#include <ssl.h>
err = SSL_set_verify (ssl, SSL_VERIFY_CLIENT_ONCE,
&your_call_back_here);
In Perl:
use Net::SSLeay;
$err = Net::SSLeay::set_verify ($ssl,
Net::SSLeay::VERIFY_CLIENT_ONCE,
\&your_call_back_here);
If the function does not start with "SSL_" you should use the full
function name, e.g.:
$err = Net::SSLeay::ERR_get_error;
The following new functions behave in perlish way:
$got = Net::SSLeay::read($ssl);
# Performs SSL_read, but returns $got
# resized according to data received.
# Returns undef on failure.
Net::SSLeay::write($ssl, $foo) || die;
# Performs SSL_write, but automatically
# figures out the size of $foo
In order to use the low level API you should start your programs with
the following incantation:
use Net::SSLeay qw(die_now die_if_ssl_error);
Net::SSLeay::load_error_strings();
Net::SSLeay::SSLeay_add_ssl_algorithms(); # Important!
Net::SSLeay::ENGINE_load_builtin_engines(); # If you want built-in engines
Net::SSLeay::ENGINE_register_all_complete(); # If you want built-in engines
Net::SSLeay::randomize();
"die_now()" and "die_if_ssl_error()" are used to conveniently print the
SSLeay error stack when something goes wrong, thusly:
Net::SSLeay::connect($ssl) or die_now("Failed SSL connect ($!)");
Net::SSLeay::write($ssl, "foo") or die_if_ssl_error("SSL write ($!)");
You can also use "Net::SSLeay::print_errs()" to dump the error stack
without exiting the program. As can be seen, your code becomes much
more readable if you import the error reporting functions into your
main name space.
I can not emphasize the need to check for error enough. Use these
functions even in the most simple programs, they will reduce debugging
time greatly. Do not ask questions on the mailing list without having
first sprinkled these in your code.
Sockets
Perl uses file handles for all I/O. While SSLeay has a quite flexible
BIO mechanism and perl has an evolved PerlIO mechanism, this module
still sticks to using file descriptors. Thus to attach SSLeay to a
socket you should use "fileno()" to extract the underlying file
descriptor:
Net::SSLeay::set_fd($ssl, fileno(S)); # Must use fileno
You should also set $| to 1 to eliminate STDIO buffering so you do not
get confused if you use perl I/O functions to manipulate your socket
handle.
If you need to select(2) on the socket, go right ahead, but be warned
that OpenSSL does some internal buffering so SSL_read does not always
return data even if the socket selected for reading (just keep on
selecting and trying to read). "Net::SSLeay" is no different from the C
language OpenSSL in this respect.
Callbacks
You can establish a per-context verify callback function something like
this:
sub verify {
my ($ok, $x509_store_ctx) = @_;
print "Verifying certificate...\n";
...
return $ok;
}
It is used like this:
Net::SSLeay::set_verify ($ssl, Net::SSLeay::VERIFY_PEER, \&verify);
Per-context callbacks for decrypting private keys are implemented.
Net::SSLeay::CTX_set_default_passwd_cb($ctx, sub { "top-secret" });
Net::SSLeay::CTX_use_PrivateKey_file($ctx, "key.pem",
Net::SSLeay::FILETYPE_PEM)
or die "Error reading private key";
Net::SSLeay::CTX_set_default_passwd_cb($ctx, undef);
If Hello Extensions are supported by your OpenSSL, a session secret
callback can be set up to be called when a session secret is set by
openssl.
Establish it like this:
Net::SSLeay::set_session_secret_cb($ssl, \&session_secret_cb,
$somedata);
It will be called like this:
sub session_secret_cb
{
my ($secret, \@cipherlist, \$preferredcipher, $somedata) = @_;
}
No other callbacks are implemented. You do not need to use any callback
for simple (i.e. normal) cases where the SSLeay built-in verify
mechanism satisfies your needs.
It is required to reset these callbacks to undef immediately after use
to prevent memory leaks, thread safety problems and crashes on exit
that can occur if different threads set different callbacks.
If you want to use callback stuff, see examples/callback.pl! Its the
only one I am able to make work reliably.
X509 and RAND stuff
This module largely lacks interface to the X509 and RAND routines, but
as I was lazy and needed them, the following kludges are implemented:
$x509_name = Net::SSLeay::X509_get_subject_name($x509_cert);
$x509_name = Net::SSLeay::X509_get_issuer_name($x509_cert);
print Net::SSLeay::X509_NAME_oneline($x509_name);
$text = Net::SSLeay::X509_NAME_get_text_by_NID($name, $nid);
($type1, $subject1, $type2, $subject2, ...) =
Net::SSLeay::X509_get_subjectAltNames($x509_cert)
subjectAltName types as per x509v3.h GEN_*, for example
GEN_DNS or GEN_IPADD which can be imported.
Net::SSLeay::RAND_seed($buf); # Perlishly figures out buf size
Net::SSLeay::RAND_bytes($buf, $num);
Net::SSLeay::RAND_pseudo_bytes($buf, $num);
Net::SSLeay::RAND_add($buf, $num, $entropy);
Net::SSLeay::RAND_poll();
Net::SSLeay::RAND_status();
Net::SSLeay::RAND_cleanup();
Net::SSLeay::RAND_file_name($num);
Net::SSLeay::RAND_load_file($file_name, $how_many_bytes);
Net::SSLeay::RAND_write_file($file_name);
Net::SSLeay::RAND_egd($path);
Net::SSLeay::RAND_egd_bytes($path, $bytes);
Actually you should consider using the following helper functions:
print Net::SSLeay::dump_peer_certificate($ssl);
Net::SSLeay::randomize();
RSA interface
Some RSA functions are available:
$rsakey = Net::SSLeay::RSA_generate_key();
Net::SSLeay::CTX_set_tmp_rsa($ctx, $rsakey);
Net::SSLeay::RSA_free($rsakey);
Digests
Some Digest functions are available if supported by the underlying
library. These may include MD2, MD4, MD5, and RIPEMD160:
$hash = Net::SSLeay::MD5($foo);
print unpack('H*', $hash);
BIO interface
Some BIO functions are available:
Net::SSLeay::BIO_s_mem();
$bio = Net::SSLeay::BIO_new(BIO_s_mem())
$bio = Net::SSLeay::BIO_new_file($filename, $mode);
Net::SSLeay::BIO_free($bio)
$count = Net::SSLeay::BIO_write($data);
$data = Net::SSLeay::BIO_read($bio);
$data = Net::SSLeay::BIO_read($bio, $maxbytes);
$is_eof = Net::SSLeay::BIO_eof($bio);
$count = Net::SSLeay::BIO_pending($bio);
$count = Net::SSLeay::BIO_wpending ($bio);
Low level API
Some very low level API functions are available:
$client_random = Net::SSLeay::get_client_random($ssl);
$server_random = Net::SSLeay::get_server_random($ssl);
$session = Net::SSLeay::get_session($ssl);
$master_key = Net::SSLeay::SESSION_get_master_key($session);
Net::SSLeay::SESSION_set_master_key($session, $master_secret);
$keyblocksize = Net::SSLeay::get_keyblock_size($session);
HTTP (without S) API
Over the years it has become clear that it would be convenient to use
the light-weight flavour API of "Net::SSLeay" for normal HTTP as well
(see "LWP" for the heavy-weight object-oriented approach). In fact it
would be nice to be able to flip https on and off on the fly. Thus
regular HTTP support was evolved.
use Net::SSLeay qw(get_http post_http tcpcat
get_httpx post_httpx tcpxcat
make_headers make_form);
($page, $result, %headers) =
= get_http('www.bacus.pt', 443, '/protected.html',
make_headers(Authorization =>
'Basic ' . MIME::Base64::encode("$user:$pass",''))
);
($page, $response, %reply_headers)
= post_http('www.bacus.pt', 443, '/foo.cgi', '',
make_form(OK => '1',
name => 'Sampo'
));
($reply, $err) = tcpcat($host, $port, $request);
($page, $result, %headers) =
= get_httpx($usessl, 'www.bacus.pt', 443, '/protected.html',
make_headers(Authorization =>
'Basic ' . MIME::Base64::encode("$user:$pass",''))
);
($page, $response, %reply_headers)
= post_httpx($usessl, 'www.bacus.pt', 443, '/foo.cgi', '',
make_form(OK => '1', name => 'Sampo' ));
($reply, $err, $server_cert) = tcpxcat($usessl, $host, $port, $request);
As can be seen, the "x" family of APIs takes as the first argument a
flag which indicates whether SSL is used or not.
EXAMPLES
One very good example to look at is the implementation of "sslcat()" in
the "SSLeay.pm" file.
The following is a simple SSLeay client (with too little error checking
:-(
#!/usr/local/bin/perl
use Socket;
use Net::SSLeay qw(die_now die_if_ssl_error) ;
Net::SSLeay::load_error_strings();
Net::SSLeay::SSLeay_add_ssl_algorithms();
Net::SSLeay::randomize();
($dest_serv, $port, $msg) = @ARGV; # Read command line
$port = getservbyname ($port, 'tcp') unless $port =~ /^\d+$/;
$dest_ip = gethostbyname ($dest_serv);
$dest_serv_params = sockaddr_in($port, $dest_ip);
socket (S, &AF_INET, &SOCK_STREAM, 0) or die "socket: $!";
connect (S, $dest_serv_params) or die "connect: $!";
select (S); $| = 1; select (STDOUT); # Eliminate STDIO buffering
# The network connection is now open, lets fire up SSL
$ctx = Net::SSLeay::CTX_new() or die_now("Failed to create SSL_CTX $!");
Net::SSLeay::CTX_set_options($ctx, &Net::SSLeay::OP_ALL)
and die_if_ssl_error("ssl ctx set options");
$ssl = Net::SSLeay::new($ctx) or die_now("Failed to create SSL $!");
Net::SSLeay::set_fd($ssl, fileno(S)); # Must use fileno
$res = Net::SSLeay::connect($ssl) and die_if_ssl_error("ssl connect");
print "Cipher `" . Net::SSLeay::get_cipher($ssl) . "'\n";
# Exchange data
$res = Net::SSLeay::write($ssl, $msg); # Perl knows how long $msg is
die_if_ssl_error("ssl write");
CORE::shutdown S, 1; # Half close --> No more output, sends EOF to server
$got = Net::SSLeay::read($ssl); # Perl returns undef on failure
die_if_ssl_error("ssl read");
print $got;
Net::SSLeay::free ($ssl); # Tear down connection
Net::SSLeay::CTX_free ($ctx);
close S;
The following is a simple SSLeay echo server (non forking):
#!/usr/local/bin/perl -w
use Socket;
use Net::SSLeay qw(die_now die_if_ssl_error);
Net::SSLeay::load_error_strings();
Net::SSLeay::SSLeay_add_ssl_algorithms();
Net::SSLeay::randomize();
$our_ip = "\0\0\0\0"; # Bind to all interfaces
$port = 1235;
$sockaddr_template = 'S n a4 x8';
$our_serv_params = pack ($sockaddr_template, &AF_INET, $port, $our_ip);
socket (S, &AF_INET, &SOCK_STREAM, 0) or die "socket: $!";
bind (S, $our_serv_params) or die "bind: $!";
listen (S, 5) or die "listen: $!";
$ctx = Net::SSLeay::CTX_new () or die_now("CTX_new ($ctx): $!");
Net::SSLeay::CTX_set_options($ctx, &Net::SSLeay::OP_ALL)
and die_if_ssl_error("ssl ctx set options");
# Following will ask password unless private key is not encrypted
Net::SSLeay::CTX_use_RSAPrivateKey_file ($ctx, 'plain-rsa.pem',
&Net::SSLeay::FILETYPE_PEM);
die_if_ssl_error("private key");
Net::SSLeay::CTX_use_certificate_file ($ctx, 'plain-cert.pem',
&Net::SSLeay::FILETYPE_PEM);
die_if_ssl_error("certificate");
while (1) {
print "Accepting connections...\n";
($addr = accept (NS, S)) or die "accept: $!";
select (NS); $| = 1; select (STDOUT); # Piping hot!
($af,$client_port,$client_ip) = unpack($sockaddr_template,$addr);
@inetaddr = unpack('C4',$client_ip);
print "$af connection from " .
join ('.', @inetaddr) . ":$client_port\n";
# We now have a network connection, lets fire up SSLeay...
$ssl = Net::SSLeay::new($ctx) or die_now("SSL_new ($ssl): $!");
Net::SSLeay::set_fd($ssl, fileno(NS));
$err = Net::SSLeay::accept($ssl) and die_if_ssl_error('ssl accept');
print "Cipher `" . Net::SSLeay::get_cipher($ssl) . "'\n";
# Connected. Exchange some data.
$got = Net::SSLeay::read($ssl); # Returns undef on fail
die_if_ssl_error("ssl read");
print "Got `$got' (" . length ($got) . " chars)\n";
Net::SSLeay::write ($ssl, uc ($got)) or die "write: $!";
die_if_ssl_error("ssl write");
Net::SSLeay::free ($ssl); # Tear down connection
close NS;
}
Yet another echo server. This one runs from "/etc/inetd.conf" so it
avoids all the socket code overhead. Only caveat is opening an rsa key
file - it had better be without any encryption or else it will not know
where to ask for the password. Note how "STDIN" and "STDOUT" are wired
to SSL.
#!/usr/local/bin/perl
# /etc/inetd.conf
# ssltst stream tcp nowait root /path/to/server.pl server.pl
# /etc/services
# ssltst 1234/tcp
use Net::SSLeay qw(die_now die_if_ssl_error);
Net::SSLeay::load_error_strings();
Net::SSLeay::SSLeay_add_ssl_algorithms();
Net::SSLeay::randomize();
chdir '/key/dir' or die "chdir: $!";
$| = 1; # Piping hot!
open LOG, ">>/dev/console" or die "Can't open log file $!";
select LOG; print "server.pl started\n";
$ctx = Net::SSLeay::CTX_new() or die_now "CTX_new ($ctx) ($!)";
$ssl = Net::SSLeay::new($ctx) or die_now "new ($ssl) ($!)";
Net::SSLeay::set_options($ssl, &Net::SSLeay::OP_ALL)
and die_if_ssl_error("ssl set options");
# We get already open network connection from inetd, now we just
# need to attach SSLeay to STDIN and STDOUT
Net::SSLeay::set_rfd($ssl, fileno(STDIN));
Net::SSLeay::set_wfd($ssl, fileno(STDOUT));
Net::SSLeay::use_RSAPrivateKey_file ($ssl, 'plain-rsa.pem',
Net::SSLeay::FILETYPE_PEM);
die_if_ssl_error("private key");
Net::SSLeay::use_certificate_file ($ssl, 'plain-cert.pem',
Net::SSLeay::FILETYPE_PEM);
die_if_ssl_error("certificate");
Net::SSLeay::accept($ssl) and die_if_ssl_err("ssl accept: $!");
print "Cipher `" . Net::SSLeay::get_cipher($ssl) . "'\n";
$got = Net::SSLeay::read($ssl);
die_if_ssl_error("ssl read");
print "Got `$got' (" . length ($got) . " chars)\n";
Net::SSLeay::write ($ssl, uc($got)) or die "write: $!";
die_if_ssl_error("ssl write");
Net::SSLeay::free ($ssl); # Tear down the connection
Net::SSLeay::CTX_free ($ctx);
close LOG;
There are also a number of example/test programs in the examples
directory:
sslecho.pl - A simple server, not unlike the one above
minicli.pl - Implements a client using low level SSLeay routines
sslcat.pl - Demonstrates using high level sslcat utility function
get_page.pl - Is a utility for getting html pages from secure servers
callback.pl - Demonstrates certificate verification and callback usage
stdio_bulk.pl - Does SSL over Unix pipes
ssl-inetd-serv.pl - SSL server that can be invoked from inetd.conf
httpd-proxy-snif.pl - Utility that allows you to see how a browser
sends https request to given server and what reply
it gets back (very educative :-)
makecert.pl - Creates a self signed cert (does not use this module)
LIMITATIONS
"Net::SSLeay::read()" uses an internal buffer of 32KB, thus no single
read will return more. In practice one read returns much less, usually
as much as fits in one network packet. To work around this, you should
use a loop like this:
$reply = '';
while ($got = Net::SSLeay::read($ssl)) {
last if print_errs('SSL_read');
$reply .= $got;
}
Although there is no built-in limit in "Net::SSLeay::write()", the
network packet size limitation applies here as well, thus use:
$written = 0;
while ($written < length($message)) {
$written += Net::SSLeay::write($ssl, substr($message, $written));
last if print_errs('SSL_write');
}
Or alternatively you can just use the following convenience functions:
Net::SSLeay::ssl_write_all($ssl, $message) or die "ssl write failure";
$got = Net::SSLeay::ssl_read_all($ssl) or die "ssl read failure";
KNOWN BUGS AND CAVEATS
Autoloader emits a
Argument "xxx" isn't numeric in entersub at blib/lib/Net/SSLeay.pm'
warning if die_if_ssl_error is made autoloadable. If you figure out
why, drop me a line.
Callback set using "SSL_set_verify()" does not appear to work. This may
well be an openssl problem (e.g. see "ssl/ssl_lib.c" line 1029). Try
using "SSL_CTX_set_verify()" instead and do not be surprised if even
this stops working in future versions.
Callback and certificate verification stuff is generally too little
tested.
Random numbers are not initialized randomly enough, especially if you
do not have "/dev/random" and/or "/dev/urandom" (such as in Solaris
platforms - but I've been suggested that cryptorand daemon from the
SUNski package solves this). In this case you should investigate third
party software that can emulate these devices, e.g. by way of a named
pipe to some program.
Another gotcha with random number initialization is randomness
depletion. This phenomenon, which has been extensively discussed in
OpenSSL, Apache-SSL, and Apache-mod_ssl forums, can cause your script
to block if you use "/dev/random" or to operate insecurely if you use
"/dev/urandom". What happens is that when too much randomness is drawn
from the operating system's randomness pool then randomness can
temporarily be unavailable. "/dev/random" solves this problem by
waiting until enough randomness can be gathered - and this can take a
long time since blocking reduces activity in the machine and less
activity provides less random events: a vicious circle. "/dev/urandom"
solves this dilemma more pragmatically by simply returning predictable
"random" numbers. Some" /dev/urandom" emulation software however
actually seems to implement "/dev/random" semantics. Caveat emptor.
I've been pointed to two such daemons by Mik Firestone
<mik@@speed.stdio._com> who has used them on Solaris 8:
1. Entropy Gathering Daemon (EGD) at
<http://www.lothar.com/tech/crypto/>
2. Pseudo-random number generating daemon (PRNGD) at
<http://www.aet.tu-cottbus.de/personen/jaenicke/postfix_tls/prngd.html>
If you are using the low level API functions to communicate with other
SSL implementations, you would do well to call
Net::SSLeay::CTX_set_options($ctx, &Net::SSLeay::OP_ALL)
and die_if_ssl_error("ssl ctx set options");
to cope with some well know bugs in some other SSL implementations. The
high level API functions always set all known compatibility options.
Sometimes "sslcat()" (and the high level HTTPS functions that build on
it) is too fast in signaling the EOF to legacy HTTPS servers. This
causes the server to return empty page. To work around this problem you
can set the global variable
$Net::SSLeay::slowly = 1; # Add sleep so broken servers can keep up
HTTP/1.1 is not supported. Specifically this module does not know to
issue or serve multiple http requests per connection. This is a serious
shortcoming, but using the SSL session cache on your server helps to
alleviate the CPU load somewhat.
As of version 1.09 many newer OpenSSL auxiliary functions were added
(from "REM_AUTOMATICALLY_GENERATED_1_09" onwards in "SSLeay.xs").
Unfortunately I have not had any opportunity to test these. Some of
them are trivial enough that I believe they "just work", but others
have rather complex interfaces with function pointers and all. In these
cases you should proceed wit great caution.
This module defaults to using OpenSSL automatic protocol negotiation
code for automatically detecting the version of the SSL protocol that
the other end talks. With most web servers this works just fine, but
once in a while I get complaints from people that the module does not
work with some web servers. Usually this can be solved by explicitly
setting the protocol version, e.g.
$Net::SSLeay::ssl_version = 2; # Insist on SSLv2
$Net::SSLeay::ssl_version = 3; # Insist on SSLv3
$Net::SSLeay::ssl_version = 10; # Insist on TLSv1
Although the autonegotiation is nice to have, the SSL standards do not
formally specify any such mechanism. Most of the world has accepted the
SSLeay/OpenSSL way of doing it as the de facto standard. But for the
few that think differently, you have to explicitly speak the correct
version. This is not really a bug, but rather a deficiency in the
standards. If a site refuses to respond or sends back some nonsensical
error codes (at the SSL handshake level), try this option before
mailing me.
The high level API returns the certificate of the peer, thus allowing
one to check what certificate was supplied. However, you will only be
able to check the certificate after the fact, i.e. you already sent
your form data by the time you find out that you did not trust them,
oops.
So, while being able to know the certificate after the fact is surely
useful, the security minded would still choose to do the connection and
certificate verification first and only then exchange data with the
site. Currently none of the high level API functions do this, thus you
would have to program it using the low level API. A good place to start
is to see how the "Net::SSLeay::http_cat()" function is implemented.
The high level API functions use a global file handle "SSLCAT_S"
internally. This really should not be a problem because there is no way
to interleave the high level API functions, unless you use threads (but
threads are not very well supported in perl anyway (as of version
5.6.1). However, you may run into problems if you call undocumented
internal functions in an interleaved fashion.
DIAGNOSTICS
Random number generator not seeded!!!
(W) This warning indicates that "randomize()" was not able to read
"/dev/random" or "/dev/urandom", possibly because your system does
not have them or they are differently named. You can still use SSL,
but the encryption will not be as strong.
open_tcp_connection: destination host not found:`server' (port 123)
($!)
Name lookup for host named "server" failed.
open_tcp_connection: failed `server', 123 ($!)
The name was resolved, but establising the TCP connection failed.
msg 123: 1 - error:140770F8:SSL routines:SSL23_GET_SERVER_HELLO:unknown
proto
SSLeay error string. The first number (123) is the PID, the second
number (1) indicates the position of the error message in SSLeay
error stack. You often see a pile of these messages as errors
cascade.
msg 123: 1 - error:02001002::lib(2) :func(1) :reason(2)
The same as above, but you didn't call load_error_strings() so
SSLeay couldn't verbosely explain the error. You can still find out
what it means with this command:
/usr/local/ssl/bin/ssleay errstr 02001002
Password is being asked for private key
This is normal behaviour if your private key is encrypted. Either
you have to supply the password or you have to use an unencrypted
private key. Scan OpenSSL.org for the FAQ that explains how to do
this (or just study examples/makecert.pl which is used during "make
test" to do just that).
BUGS AND SUPPORT
Please report any bugs or feature requests to "bug-Net-SSLeay at
rt.cpan.org", or through the web interface at
<http://rt.cpan.org/Public/Dist/Display.html?Name=Net-SSLeay>. I will
be notified, and then you'll automatically be notified of progress on
your bug as I make changes.
Subversion access to the latest source code etc can be obtained at
<http://alioth.debian.org/projects/net-ssleay>
The developer mailing list (for people interested in contributing to
the source code) can be found at
<http://lists.alioth.debian.org/mailman/listinfo/net-ssleay-devel>
You can find documentation for this module with the "perldoc" command.
perldoc Net::SSLeay
You can also look for information at:
· AnnoCPAN: Annotated CPAN documentation
<http://annocpan.org/dist/Net-SSLeay>
· CPAN Ratings
<http://cpanratings.perl.org/d/Net-SSLeay>
· Search CPAN
<http://search.cpan.org/dist/Net-SSLeay>
Commercial support for Net::SSLeay may be obtained from
Symlabs (netssleay@symlabs.com)
Tel: +351-214.222.630
Fax: +351-214.222.637
AUTHOR
Maintained by Mike McCauley and Florian Ragwitz since November 2005
Originally written by Sampo Kellomaeki <sampo@symlabs.com>
COPYRIGHT
Copyright (c) 1996-2003 Sampo Kellomaeki <sampo@symlabs.com>
Copyright (C) 2005-2006 Florian Ragwitz <rafl@debian.org>
Copyright (C) 2005 Mike McCauley <mikem@open.com.au>
All Rights Reserved.
Distribution and use of this module is under the same terms as the
OpenSSL package itself (i.e. free, but mandatory attribution; NO
WARRANTY). Please consult LICENSE file in the root of the OpenSSL
distribution.
While the source distribution of this perl module does not contain
Eric's or OpenSSL's code, if you use this module you will use OpenSSL
library. Please give Eric and OpenSSL team credit (as required by their
licenses).
And remember, you, and nobody else but you, are responsible for
auditing this module and OpenSSL library for security problems,
backdoors, and general suitability for your application.
SEE ALSO
Net::SSLeay::Handle - File handle interface
./examples - Example servers and a clients
<http://www.openssl.org/> - OpenSSL source, documentation, etc
openssl-users-request@openssl.org - General OpenSSL mailing list
<http://www.ietf.org/rfc/rfc2246.txt> - TLS 1.0 specification
<http://www.w3c.org> - HTTP specifications
<http://www.ietf.org/rfc/rfc2617.txt> - How to send password
<http://www.lothar.com/tech/crypto/> - Entropy Gathering Daemon (EGD)
<http://www.aet.tu-cottbus.de/personen/jaenicke/postfix_tls/prngd.html>
- pseudo-random number generating daemon (PRNGD)
perl(1)perlref(1)perllol(1)
perldoc ~openssl/doc/ssl/SSL_CTX_set_verify.pod
perl v5.10.1 2010-01-30 Net::SSLeay(3pm)
