Net::SSLeay(3) User Contributed Perl Documentation Net::SSLeay(3)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 convinience functions for accessing
web pages on SSL servers (for symmetry, same API is offered for access‐
ing 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 argu‐
ment is the TCP port at the remote end (your own port is picked arbi‐
trarily 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 con‐
vert 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 format‐
ting, 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 eas‐
ily 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 $trace global variable can be used to control the verbosity of high
level functions. Level 0 guarantees silence, level 1 (the default) only
emits error messages.
Alternate versions of the API
The above mentioned functions actually return the response headers as a
list, which only gets converted to hash upon assignment (this assign‐
ment looses information if the same header occurs twice, as may be the
case with cookies). There are also other variants of the functions that
return unprocessed headers and that return a reference to a hash.
($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 head‐
ers 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($server_cert));
}
Beware that this method only allows after the fact verification of the
certificate: by the time "get_https3()" has returned the https request
has already been sent to the server, whether you decide to tryst it or
not. To do the verification correctly you must either employ the
OpenSSL certificate verification framework or use the lower level API
to first connect and verify the certificate and only then send the http
data. See implementation of "ds_https3()" for guidance on how to do
this.
Using client certificates
Secure web communications are encrypted using symmetric crypto keys
exchanged using encryption based on the certificate of the server.
Therefore in all SSL connections the server must have a certificate.
This serves both to authenticate the server to the clients and to per‐
form the key exchange.
Sometimes it is necessary to authenticate the client as well. Two
options are available: HTTP basic authentication and client side cer‐
tificate. The basic authentication over HTTPS is actually quite safe
because HTTPS guarantees that the password will not travel in clear.
Never-the-less, problems like easily guessable passwords remain. The
client certificate method involves authentication of the client at SSL
level using a certificate. For this to work, both the client and the
server will have certificates (which typically are different) and pri‐
vate keys.
The API functions outlined above accept additional arguments that allow
one to supply the client side certificate and key files. The format of
these files is the same as used for server certificates and the caveat
about encrypting private key applies.
($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, $path_to_key8);
Case 2c demonstrates getting password protected page that also requires
client certificate, i.e. it is possible to use both authentication
methods simultaneously.
Case 3b is full blown post to secure server that requires both password
authentication and client certificate, just like in case 2c.
Note: Client will not send a certificate unless the server requests
one. This is typically achieved by setting verify mode to "VER‐
IFY_PEER" on the server:
Net::SSLeay::set_verify(ssl, Net::SSLeay::VERIFY_PEER, 0);
See "perldoc ~openssl/doc/ssl/SSL_CTX_set_verify.pod" for full descrip‐
tion.
Working through Web proxy
"Net::SSLeay" can use a web proxy to make its connections. You need to
first set the proxy host and port using "set_proxy()" and then just use
the normal API functions, e.g:
Net::SSLeay::set_proxy('gateway.myorg.com', 8080);
($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, $result, %headers) =
= get_https('www.bacus.pt', 443, '/protected.html',
make_headers(Authorization =>
'Basic ' . MIME::Base64::encode("susie:pass",''))
);
This example demonstrates case where we authenticate to the proxy as
"joe" and to the final web server as "susie". Proxy authentication
requires "MIME::Base64" module to work.
Certificate verification and Certificate Revoocation Lists (CRLs)
OpenSSL supports the ability to verify peer certificates. It can also
optionally check the peer certificate against a Certificate Revocation
List (CRL) from the certificates issuer. A CRL is a file, created by
the certificate issuer that lists all the certificates that it previ‐
ously signed, but which it now revokes. CRLs are in PEM format.
You can enable "Net::SSLeay CRL" checking like this:
&Net::SSLeay::X509_STORE_CTX_set_flags
(&Net::SSLeay::CTX_get_cert_store($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 imple‐
mented 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 func‐
tion 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 $⎪ to 1 to eliminate STDIO buffering so you do not
get confused if you use perl I/O functions to manipulate your socket
handle.
If you need to select(2) on the socket, go right ahead, but be warned
that OpenSSL does some internal buffering so SSL_read does not always
return data even if socket selected for reading (just keep on selecting
and trying to read). "Net::SSLeay" is no different from the C language
OpenSSL in this respect.
Callbacks
At this moment the implementation of verify_callback is crippeled in
the sense that at any given time there can be only one call back which
is shared by all SSL contexts, sessions and connections. This is due to
having to keep the reference to the perl call back in a static variable
so that the callback C glue can find it. To remove this restriction
would require either a more complex data structure (like a hash?) in
XSUB to map the call backs to their owners or, cleaner, adding a con‐
text pointer in the SSL structure. This context would then be passed to
the C callback, which in our case would be the glue to look up the
proper Perl function from the context and call it.
---- inaccurate ---- The verify call back looks like this in C:
int (*callback)(int ok,X509 *subj_cert,X509 *issuer_cert,
int depth,int errorcode,char *arg,STACK *cert_chain)
The corresponding Perl function should be something like this:
sub verify {
my ($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 mecha‐
nism 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 direc‐
tory:
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 net‐
work 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 deple‐
tion. 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 tempo‐
rarily 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 pro‐
vides 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/post‐
fix_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 alle‐
viate 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 stan‐
dards. 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" inter‐
nally. 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 pri‐
vate 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/mail‐
man/listinfo/net-ssleay-devel>
Commercial support for Net::SSLeay may be obtained from
Symlabs (netssleay@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 mak‐
ing a simple SSL connection over TCP socket. Presumably Eric's own mod‐
ule will offer full SSLeay API one day.
This module uses OpenSSL-0.9.6c. It does not work with any earlier ver‐
sion 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/Pub‐
lic/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:
* AnnoCPAN: Annotated CPAN documentation
<http://annocpan.org/dist/Net_SSLeay.pm>
* CPAN Ratings
<http://cpanratings.perl.org/d/Net_SSLeay.pm>
* RT: CPAN's request tracker
<http://rt.cpan.org/Public/Dist/Display.html?Name=Net_SSLeay.pm>
* 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 Kellom�ki <sampo@symlabs.com>
COPYRIGHT
Copyright (c) 1996-2003 Sampo Kellom�ki <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 WAR‐
RANTY). Please consult LICENSE file in the root of the OpenSSL distri‐
bution.
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 audit‐
ing 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@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
perl v5.8.8 2008-07-25 Net::SSLeay(3)