Net::SSLeay(3) User Contributed Perl Documentation Net::SSLeay(3)
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 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] . "
";
}
($page, $response, $headers, $server_cert)
= get_https3('www.bacus.pt', 443, '/');
print "$headers
";
($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
";
}
}
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, "
" 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...
";
...
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, $request);
As can be seen, the "x" family of APIs takes as the first argument a flag which indicates whether SSL is used or not.
EXAMPLES
One very good example to look at is the implementation of "sslcat()" in the "SSLeay.pm" file.
The following is a simple SSLeay client (with too little error checking :-(
#!/usr/bin/perl
use Socket;
use Net::SSLeay qw(die_now die_if_ssl_error) ;
Net::SSLeay::load_error_strings();
Net::SSLeay::SSLeay_add_ssl_algorithms();
Net::SSLeay::randomize();
($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) . "'
";
# 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/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 = "