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Net::SSLeay(3pm) User Contributed Perl Documentation Net::SSLeay(3pm)
NAME
Net::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 convinience functions for accessing web pages on SSL
servers (for symmetry, same API is offered for accessing http servers, too), a "sslcat()"
function for writing your own clients, and finally access to the SSL api of SSLeay/OpenSSL
package so you can write servers or clients for more complicated applications.
For high level functions it is most convinient to import them to your main namespace as
indicated in the synopsis.
Case 1 demonstrates typical invocation of get_https() to fetch an HTML page from secure
server. The first argument provides host name or ip in dotted decimal notation of the
remote server to contact. 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 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" (make virtual
hosting easy) and "Accept" (reportedly needed by IIS) headers.
Case 2b demonstrates how to get password protected page. Refer to HTTP protocol
specifications for further details (e.g. RFC-2617).
Case 3 invokes "post_https()" to submit a HTML/CGI form to secure server. First four
arguments are equal to "get_https()" (note that 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. The "post_https()" automatically adds
"Content-Type" and "Content-Length" headers to the request.
Case 4 shows the fundamental "sslcat()" function (inspired in spirit by "netcat" utility
:-). Its 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 return of errors as well as the
server (peer) certificate.
The $trace global variable can be used to control the verbosity of high level functions.
Level 0 guarantees silence, level 1 (the default) only emits error messages.
Alternate versions of the API
The above mentioned functions actually return the response headers as a list, which only
gets converted to hash upon assignment (this assignment looses information if the same
header occurs twice, as may be the case with cookies). There are also other variants of
the functions that return unprocessed headers and that return a reference to a hash.
($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 hash of arrays (see perlref and perllol if you are not familiar with complex
perl data structures). To access single value of such header hash you would do something
like
print $headers_ref{COOKIE}[0];
The variants 3 and 4 also allow you to discover the server certificate in case you would
like to store or display it, e.g.
($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($server_cert));
}
Beware that this method only allows after the fact verification of the certificate: by the
time "get_https3()" has returned the https request has already been sent to the server,
whether you decide to tryst it or not. To do the verification correctly you must either
employ the OpenSSL certificate verification framework or use the lower level API to first
connect and verify the certificate and only then send the http data. See implementation of
"ds_https3()" for guidance on how to do this.
Using client certificates
Secure web communications are encrypted using symmetric crypto keys exchanged using
encryption based on the certificate of the server. Therefore in all SSL connections the
server must have a certificate. This serves both to authenticate the server to the clients
and to perform the key exchange.
Sometimes it is necessary to authenticate the client as well. Two options are available:
HTTP basic authentication and client side certificate. The basic authentication over HTTPS
is actually quite safe because HTTPS guarantees that the password will not travel in
clear. Never-the-less, problems like easily guessable passwords remain. The client
certificate method involves authentication of the client at SSL level using a certificate.
For this to work, both the client and the server will have certificates (which typically
are different) and private keys.
The API functions outlined above accept additional arguments that allow one to supply the
client side certificate and key files. The format of these files is the same as used for
server certificates and the caveat about encrypting private key applies.
($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, $path_to_key8);
Case 2c demonstrates getting password protected page that also requires client
certificate, i.e. it is possible to use both authentication methods simultaneously.
Case 3b is full blown post to secure server that requires both password authentication and
client certificate, just like in case 2c.
Note: Client will not send a certificate unless the server requests one. This is
typically achieved by setting verify mode to "VERIFY_PEER" on the server:
Net::SSLeay::set_verify(ssl, Net::SSLeay::VERIFY_PEER, 0);
See "perldoc ~openssl/doc/ssl/SSL_CTX_set_verify.pod" for full description.
Working through Web proxy
"Net::SSLeay" can use a web proxy to make its connections. You need to first set the proxy
host and port using "set_proxy()" and then just use the normal API functions, e.g:
Net::SSLeay::set_proxy('gateway.myorg.com', 8080);
($page) = get_https('www.bacus.pt', 443, '/');
If your proxy requires authentication, you can supply username and password as well
Net::SSLeay::set_proxy('gateway.myorg.com', 8080, 'joe', 'salainen');
($page, $result, %headers) =
= get_https('www.bacus.pt', 443, '/protected.html',
make_headers(Authorization =>
'Basic ' . MIME::Base64::encode("susie:pass",''))
);
This example demonstrates case where we authenticate to the proxy as "joe" and to the
final web server as "susie". Proxy authentication requires "MIME::Base64" module to work.
Certificate verification and Certificate Revoocation Lists (CRLs)
OpenSSL supports the ability to verify peer certificates. It can also optionally check the
peer certificate against a Certificate Revocation List (CRL) from the certificates issuer.
A CRL is a file, created by the certificate issuer that lists all the certificates that it
previously signed, but which it now revokes. CRLs are in PEM format.
You can enable "Net::SSLeay CRL" checking like this:
&Net::SSLeay::X509_STORE_CTX_set_flags
(&Net::SSLeay::CTX_get_cert_store($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 eay PRNG with "/dev/urandom" (see 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 plaintext description of the certificate the
peer (usually 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 reference. This is helpful to avoid unnecessary copy 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 "ssl.h" header from OpenSSL C distribution for list of low lever SSLeay functions to
call (to check if some function has been implemented see directly in SSLeay.xs). The
module strips SSLeay names of the initial "SSL_", generally you should use "Net::SSLeay::"
in 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 by "SSL_" you should use the full function name, e.g.:
$err = Net::SSLeay::ERR_get_error;
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 $foo
In order to use the low level API you should start your programs with the following
incantation:
use Net::SSLeay qw(die_now die_if_ssl_error);
Net::SSLeay::load_error_strings();
Net::SSLeay::SSLeay_add_ssl_algorithms(); # Important!
Net::SSLeay::ENGINE_load_builtin_engines(); # If you want built-in engines
Net::SSLeay::ENGINE_register_all_complete(); # If you want built-in engines
Net::SSLeay::randomize();
"die_now()" and "die_if_ssl_error()" are used to conveniently print SSLeay error stack
when something goes wrong, thusly:
Net::SSLeay::connect($ssl) or die_now("Failed SSL connect ($!)");
Net::SSLeay::write($ssl, "foo") or die_if_ssl_error("SSL write ($!)");
You can also use "Net::SSLeay::print_errs()" to dump the error stack without exiting the
program. As can be seen, your code becomes much more readable if you import the error
reporting functions to your main name space.
I can not emphasize enough the need to check error returns. Use these functions even in
most simple programs, they will reduce debugging time greatly. Do not ask questions in
mailing list without having first sprinkled these in your code.
Sockets
Perl uses file handles for all I/O. While SSLeay has quite flexible BIO mechanism and perl
has evolved PerlIO mechanism, this module still sticks to using file descriptors. Thus to
attach SSLeay to socket you should use "fileno()" to extract the underlying file
descriptor:
Net::SSLeay::set_fd($ssl, fileno(S)); # Must use fileno
You should also set $| to 1 to eliminate STDIO buffering so you do not get confused if you
use perl I/O functions to manipulate your socket handle.
If you need to select(2) on the socket, go right ahead, but be warned that OpenSSL does
some internal buffering so SSL_read does not always return data even if socket selected
for reading (just keep on selecting and trying to read). "Net::SSLeay" is no different
from the C language OpenSSL in this respect.
Callbacks
At this moment the implementation of verify_callback is crippeled in the sense that at any
given time there can be only one call back which is shared by all SSL contexts, sessions
and connections. This is due to having to keep the reference to the perl call back in a
static variable so that the callback C glue can find it. To remove this restriction would
require either a more complex data structure (like a hash?) in XSUB to map the call backs
to their owners or, cleaner, adding a context pointer in the SSL structure. This context
would then be passed to the C callback, which in our case would be the glue to look up the
proper Perl function from the context and call it.
---- inaccurate ---- The verify call back looks like this in C:
int (*callback)(int ok,X509 *subj_cert,X509 *issuer_cert,
int depth,int errorcode,char *arg,STACK *cert_chain)
The corresponding Perl function should be something like this:
sub verify {
my ($ok, $subj_cert, $issuer_cert, $depth, $errorcode,
$arg, $chain) = @_;
print "Verifying certificate...\n";
...
return $ok;
}
It is used like this:
Net::SSLeay::set_verify ($ssl, Net::SSLeay::VERIFY_PEER, \&verify);
Callbacks for decrypting private keys are implemented, but have the same limitation as the
verify_callback implementation (one password callback shared between all contexts.) You
might use it something like this:
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);
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 desirable to reset these callbacks to undef immediately after use to prevent thread
safety problems and crashes on exit that can occur if different threads set different
callbacks.
---- end inaccurate ----
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);
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" also for normal HTTP (see LWP for 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, $request);
As can be seen, the "x" family of APIs takes as first argument a flag which indicated
whether SSL is used or not.
EXAMPLES
One very good example is to look at the implementation of "sslcat()" in the "SSLeay.pm"
file.
Following is a simple SSLeay client (with too little error checking :-(
#!/usr/local/bin/perl
use Socket;
use Net::SSLeay qw(die_now die_if_ssl_error) ;
Net::SSLeay::load_error_strings();
Net::SSLeay::SSLeay_add_ssl_algorithms();
Net::SSLeay::randomize();
($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;
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 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 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, $written));
last if print_errs('SSL_write');
}
Or alternatively you can just use the following convinence functions:
Net::SSLeay::ssl_write_all($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
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 eay
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 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 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 short coming, but using 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 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
after that 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 "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. First (123) number is PID, 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 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).
REPORTING BUGS AND SUPPORT
Bug reports, patch submission, feature requests, 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 contributin to the source code) can
be found at <http://lists.alioth.debian.org/mailman/listinfo/net-ssleay-devel>
Commercial support for Net::SSLeay may be obtained from
Symlabs (netssleay AT symlabs.com)
Tel: +351-214.222.630
Fax: +351-214.222.637
VERSION
There are currently two perl modules for using OpenSSL C library: "Net::SSLeay" (maintaned
by me) and "SSLeay" (maintained by OpenSSL team). This module is the "Net::SSLeay"
variant.
At the time of making this release, Eric's module was still quite sketchy and could not be
used for real work, thus I felt motivated to make this maintenance release. This module is
not planned to evolve to contain any further functionality, i.e. I will concentrate on
just making a simple SSL connection over TCP socket. Presumably Eric's own module will
offer full SSLeay API one day.
This module uses OpenSSL-0.9.6c. It does not work with any earlier version and there is no
guarantee that it will work with later versions either, though as long as C API does not
change, it should. This module requires Perl 5.005 or newer, though I believe it would
build with Perl 5.002 or newer.
BUGS
Please report any bugs or feature requests to "bug-net_ssleay.pm at rt.cpan.org", or
through the web interface at
<http://rt.cpan.org/Public/Dist/Display.html?Name=Net_SSLeay.pm>. I will be notified, and
then you'll automatically be notified of progress on your bug as I make changes.
SUPPORT
You can find documentation for this module with the "perldoc" command.
perldoc Net::SSLeay
You can also look for information at:
o AnnoCPAN: Annotated CPAN documentation
<http://annocpan.org/dist/Net_SSLeay.pm>
o CPAN Ratings
<http://cpanratings.perl.org/d/Net_SSLeay.pm>
o RT: CPAN's request tracker
<http://rt.cpan.org/Public/Dist/Display.html?Name=Net_SSLeay.pm>
o Search CPAN
<http://search.cpan.org/dist/Net_SSLeay.pm>
AUTHOR
Maintained by Mike McCauley and Florian Ragwitz since November 2005
Originally written by Sampo Kellomaeki <sampo AT symlabs.com>
COPYRIGHT
Copyright (c) 1996-2003 Sampo Kellomaeki <sampo AT symlabs.com>
Copyright (C) 2005-2006 Florian Ragwitz <rafl AT debian.org>
Copyright (C) 2005 Mike McCauley <mikem AT open.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
./Net_SSLeay/examples - Example servers and a clients
<http://symlabs.com/Net_SSLeay/index.html> - Net::SSLeay.pm home
<http://symlabs.com/Net_SSLeay/smime.html> - Another module using OpenSSL
<http://www.openssl.org/> - OpenSSL source, documentation, etc
openssl-users-request AT openssl.org - General OpenSSL mailing list
<http://home.netscape.com/newsref/std/SSL.html> - SSL Draft 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
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