SSLeay(3) User Contributed Perl Documentation SSLeay(3)
NAME
Net::SSLeay - Perl extension for using OpenSSL
SYNOPSIS
use Net::SSLeay, qw(gethttps posthttps sslcat makeheaders makeform);
($page) = gethttps('www.bacus.pt', 443, '/'); # 1
($page, $response, %replyheaders)
= gethttps('www.bacus.pt', 443, '/', # 2
makeheaders(User-Agent => 'Cryptozilla/5.0b1',
Referer => 'https://www.bacus.pt'
));
($page, $result, %headers) = # 2b
= gethttps('www.bacus.pt', 443, '/protected.html',
makeheaders(Authorization =>
'Basic ' . MIME::Base64::encode("$user:$pass",''))
);
($page, $response, %replyheaders)
= posthttps('www.bacus.pt', 443, '/foo.cgi', '', # 3
makeform(OK => '1',
name => 'Sampo'
));
$reply = sslcat($host, $port, $request); # 4
($reply, $err, $servercert) = sslcat($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 gethttps() 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
Case 2 demonstrates full fledged use of gethttps(). As can be seen,
gethttps() 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 gethttps() is used to insert some additional
headers in the request. makeheaders() is a function that will convert
a list or hash to such headers. By default gethttps() 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. RFC2617).
Case 3 invokes posthttps() to submit a HTML/CGI form to secure server.
First four arguments are equal to gethttps() (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 makehttps() is used to do the formatting, but you
could pass any string. The posthttps() 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 $trace global variable can be used to control the verbosity of high
level functions. Level 0 guarantees silence, level 1 (the default) only
emits error messages.
AAlltteerrnnaattee vveerrssiioonnss ooff tthhee AAPPII
The above mentioned functions actually return the response headers as a
list, which only gets converted to hash upon assignment (this
assignment looses information if the same header occurs twice, as may
be the case with cookies). There are also other variants of the
functions that return unprocessed headers and that return a reference
to a hash.
($page, $response, @headers) = gethttps('www.bacus.pt', 443, '/');
for ($i = 0; $i < $#headers; $i+=2) {
print "$headers[$i] = " . $headers[$i+1] . "\n";
}
($page, $response, $headers, $servercert)
= gethttps3('www.bacus.pt', 443, '/');
print "$headers\n";
($page, $response, %headersref, $servercert)
= gethttps4('www.bacus.pt', 443, '/');
for $k (sort keys %{headersref}) {
for $v (@{$headersref{$k}}) {
print "$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 manual pages if you are not familiar
with complex perl data structures). To access single value of such
header hash you would do something like
print $headersref{COOKIE}[0];
The variants 3 and 4 also allow you to discover the server certificate
in case you would like to store or display it, e.g.
($p, $resp, $hdrs, $servercert) = gethttps3('www.bacus.pt', 443, '/');
if (!defined($servercert) || ($servercert == 0)) {
warn "Subject Name: undefined, Issuer Name: undefined";
} else {
warn 'Subject Name: '
. Net::SSLeay::X509NAMEoneline(
Net::SSLeay::X509getsubjectname($servercert))
. 'Issuer Name: '
. Net::SSLeay::X509NAMEoneline(
Net::SSLeay::X509getissuername($servercert));
}
Beware that this method only allows after the fact verification of the
certificate: by the time gethttps3() has returned the https request
has already been sent to the server, whether you decide to tryst it or
not. To do the verification correctly you must either employ the
OpenSSL certificate verification framework or use the lower level API
to first connect and verify the certificate and only then send the http
data. See implementation of dshttps3() for guidance on how to do this.
UUssiinngg cclliieenntt cceerrttiiffiiccaatteess
Secure web communications are encrypted using symmetric crypto keys
exchanged using encryption based on the certificate of the server.
Therefore in all SSL connections the server must have a certificate.
This serves both to authenticate the server to the clients and to
perform the key exchange.
Sometimes it is necessary to authenticate the client as well. Two
options are available: http basic authentication and client side
certificate. The basic authentication over https is actually quite safe
because https guarantees that the password will not travel in clear.
Never-the-less, problems like easily guessable passwords remain. The
client certificate method involves authentication of the client at SSL
level using a certificate. For this to work, both the client and the
server will have certificates (which typically are different) and
private keys.
The API functions outlined above accept additional arguments that allow
one to supply the client side certificate and key files. The format of
these files is the same as used for server certificates and the caveat
about encrypting private key applies.
($page, $result, %headers) = # 2c
= gethttps('www.bacus.pt', 443, '/protected.html',
makeheaders(Authorization =>
'Basic ' . MIME::Base64::encode("$user:$pass",'')),
'', $mimetype6, $pathtocrt7, $pathtokey8);
($page, $response, %replyheaders)
= posthttps('www.bacus.pt', 443, '/foo.cgi', # 3b
makeheaders('Authorization' =>
'Basic ' . MIME::Base64::encode("$user:$pass",'')),
makeform(OK => '1', name => 'Sampo'),
$mimetype6, $pathtocrt7, $pathtokey8);
Case 2c demonstrates getting password protected page that also requires
client certificate, i.e. it is possible to use both authentication
methods simultaneously.
Case 3b is full blown post to secure server that requires both password
authentication and client certificate, just like in case 2c.
Note: Client will not send a certificate unless the server requests
one. This is typically achieved by setting verify mode to VERIFYPEER
on the server:
Net::SSLeay::setverify(ssl, Net::SSLeay::VERIFYPEER, 0);
See perldoc ~openssl/doc/ssl/SSLCTXsetverify.pod for full
description.
WWoorrkkiinngg tthhrroouugghh WWeebb pprrooxxyy
Net::SSLeay can use a web proxy to make its connections. You need to
first set the proxy host and port using setproxy() and then just use
the normal API functions, e.g:
Net::SSLeay::setproxy('gateway.myorg.com', 8080);
($page) = gethttps('www.bacus.pt', 443, '/');
If your proxy requires authentication, you can supply username and
password as well
Net::SSLeay::setproxy('gateway.myorg.com', 8080, 'joe', 'salainen');
($page, $result, %headers) =
= gethttps('www.bacus.pt', 443, '/protected.html',
makeheaders(Authorization =>
'Basic ' . MIME::Base64::encode("susie:pass",''))
);
This example demonstrates case where we authenticate to the proxy as
"joe" and to the final web server as "susie". Proxy authentication
requires MIME::Base64 module to work.
CCeerrttiiffiiccaattee vveerriiffiiccaattiioonn aanndd CCeerrttiiffiiccaattee RReevvooooccaattiioonn LLiissttss ((CCRRLLss))
OpenSSL supports the ability to verify peer certificates. It can also
optionally check the peer certificate against a Certificate Revocation
List (CRL) from the certificates issuer. A CRL is a file, created by
the certificate issuer that lists all the certificates that it
previously signed, but which it now revokes. CRLs are in PEM format.
You can enable Net::SSLeay CRL checking like this:
&Net::SSLeay::X509STORECTXsetflags
(&Net::SSLeay::CTXgetcertstore($ssl),
&Net::SSLeay::X509VFLAGCRLCHECK);
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
CTXloadverifylocations. 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 $bio = &Net::SSLeay::BIOnewfile($crlfilename, 'r'); my $crl =
&Net::SSLeay::PEMreadbioX509CRL($bio); if ($crl) {
&Net::SSLeay::X509STOREaddcrl(&Net::SSLeay::CTXgetcertstore($ssl,
$crl); } else {
error reading CRL.... }
CCoonnvveenniieennccee rroouuttiinneess
To be used with Low level API
Net::SSLeay::randomize($rnseedfile,$additionalseed);
Net::SSLeay::setcertandkey($ctx, $certpath, $keypath);
$cert = Net::SSLeay::dumppeercertificate($ssl);
Net::SSLeay::sslwriteall($ssl, $message) or die "ssl write failure";
$got = Net::SSLeay::sslreadall($ssl) or die "ssl read failure";
$got = Net::SSLeay::sslreadCRLF($ssl [, $maxlength]);
$got = Net::SSLeay::sslreaduntil($ssl [, $delimit [, $maxlength]]);
Net::SSLeay::sslwriteCRLF($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.
setcertandkey() 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.
dumppeercertificate() allows you to get plaintext description of the
certificate the peer (usually server) presented to us.
sslreadall() and sslwriteall() 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 sslwriteall() can be
reference. This is helpful to avoid unnecessary copy when writing
something big, e.g:
$data = 'A' x 1000000000;
Net::SSLeay::sslwriteall($ssl, \$data) or die "ssl write failed";
sslreadCRLF() uses sslreadall() to read in a line terminated with a
carriage return followed by a linefeed (CRLF). The CRLF is included in
the returned scalar.
sslreaduntil() uses sslreadall() 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.
sslwriteCRLF() writes $message and appends CRLF to the SSL output
stream.
LLooww lleevveell AAPPII
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
err = SSLsetverify (ssl, SSLVERIFYCLIENTONCE,
&yourcallbackhere);
In perl:
use Net::SSLeay;
$err = Net::SSLeay::setverify ($ssl,
&Net::SSLeay::VERIFYCLIENTONCE,
\&yourcallbackhere);
If the function does not start by SSL you should use the full function
name, e.g.:
$err = &Net::SSLeay::ERRgeterror;
Following new functions behave in perlish way:
$got = Net::SSLeay::read($ssl);
# Performs SSLread, but returns $got
# resized according to data received.
# Returns undef on failure.
Net::SSLeay::write($ssl, $foo) || die;
# Performs SSLwrite, but automatically
# figures out the size of $foo
In order to use the low level API you should start your programs with
the following encantation:
use Net::SSLeay qw(dienow dieifsslerror);
Net::SSLeay::loaderrorstrings();
Net::SSLeay::SSLeayaddsslalgorithms(); # Important!
Net::SSLeay::randomize();
dienow() and dieifsslerror() are used to conveniently print SSLeay
error stack when something goes wrong, thusly:
Net::SSLeay:connect($ssl) or dienow("Failed SSL connect ($!)");
Net::SSLeay::write($ssl, "foo") or dieifsslerror("SSL write ($!)");
You can also use Net::SSLeay::printerrs() to dump the error stack
without exiting the program. As can be seen, your code becomes much
more readable if you import the error reporting functions to your main
name space.
I can not emphasize enough the need to check error returns. Use these
functions even in most simple programs, they will reduce debugging time
greatly. Do not ask questions in mailing list without having first
sprinkled these in your code.
SSoocckkeettss
Perl uses file handles for all I/O. While SSLeay has quite flexible BIO
mechanism and perl has evolved PerlIO mechanism, this module still
sticks to using file descriptors. Thus to attach SSLeay to socket you
should use fileno() to extract the underlying file descriptor:
Net::SSLeay::setfd($ssl, fileno(S)); # Must use fileno
You should also use "$|=1;" to eliminate STDIO buffering so you do not
get confused if you use perl I/O functions to manipulate your socket
handle.
If you need to select(2) on the socket, go right ahead, but be warned
that OpenSSL does some internal buffering so SSLread does not always
return data even if socket selected for reading (just keep on selecting
and trying to read). Net::SSLeay.pm is no different from the C language
OpenSSL in this respect.
CCaallllbbaacckkss
At this moment the implementation of verifycallback is crippeled in
the sense that at any given time there can be only one call back which
is shared by all SSL contexts, sessions and connections. This is due to
having to keep the reference to the perl call back in a static variable
so that the callback C glue can find it. To remove this restriction
would require either a more complex data structure (like a hash?) in
XSUB to map the call backs to their owners or, cleaner, adding a
context pointer in the SSL structure. This context would then be passed
to the C callback, which in our case would be the glue to look up the
proper Perl function from the context and call it.
-- inaccurate -- The verify call back looks like this in C:
int (*callback)(int ok,X509 *subjcert,X509 *issuercert,
int depth,int errorcode,char *arg,STACK *certchain)
The corresponding Perl function should be something like this:
sub verify {
my ($ok, $subjcert, $issuercert, $depth, $errorcode,
$arg, $chain) = @;
print "Verifying certificate...\n";
...
return $ok;
}
It is used like this:
Net::SSLeay::setverify ($ssl, Net::SSLeay::VERIFYPEER, \&verify);
Callbacks for decrypting private keys are implemented, but have the
same limitation as the verifycallback implementation (one password
callback shared between all contexts.) You might use it something like
this:
Net::SSLeay::CTXsetdefaultpasswdcb($ctx, sub { "top-secret" });
Net::SSLeay::CTXusePrivateKeyfile($ctx, "key.pem",
Net::SSLeay::FILETYPEPEM)
or die "Error reading private key";
Net::SSLeay::CTXsetdefaultpasswdcb($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.
XX550099 aanndd RRAANNDD ssttuuffff
This module largely lacks interface to the X509 and RAND routines, but
as I was lazy and needed them, the following kludges are implemented:
$x509name = Net::SSLeay::X509getsubjectname($x509cert);
$x509name = Net::SSLeay::X509getissuername($x509cert);
print Net::SSLeay::X509NAMEoneline($x509name);
$text = Net::SSLeay::X509NAMEgettextbyNID($name, $nid);
Net::SSLeay::RANDseed($buf); # Perlishly figures out buf size
Net::SSLeay::RANDbytes($buf, $num);
Net::SSLeay::RANDpseudobytes($buf, $num);
Net::SSLeay::RANDadd($buf, $num, $entropy);
Net::SSLeay::RANDpoll();
Net::SSLeay::RANDstatus();
Net::SSLeay::RANDcleanup();
Net::SSLeay::RANDfilename($num);
Net::SSLeay::RANDloadfile($filename, $howmanybytes);
Net::SSLeay::RANDwritefile($filename);
Net::SSLeay::RANDegd($path);
Net::SSLeay::RANDegdbytes($path, $bytes);
Actually you should consider using the following helper functions:
print Net::SSLeay::dumppeercertificate($ssl);
Net::SSLeay::randomize();
RRSSAA iinntteerrffaaccee
Some RSA functions are available:
$rsakey = Net::SSLeay::RSAgeneratekey();
Net::SSLeay::CTXsettmprsa($ctx, $rsakey);
Net::SSLeay::RSAfree($rsakey);
BBIIOO iinntteerrffaaccee
Some BIO functions are available:
Net::SSLeay::BIOsmem();
$bio = Net::SSLeay::BIOnew(BIOsmem())
$bio = Net::SSLeay::BIOnewfile($filename, $mode);
Net::SSLeay::BIOfree($bio)
$count = Net::SSLeay::BIOwrite($data);
$data = Net::SSLeay::BIOread($bio);
$data = Net::SSLeay::BIOread($bio, $maxbytes);
$iseof = Net::SSLeay::BIOeof($bio);
$count = Net::SSLeay::BIOpending($bio);
$count = Net::SSLeay::BIOwpending ($bio);
LLooww lleevveell AAPPII
Some very low level API functions are available:
$clientrandom = &Net::SSLeay::getclientrandom($ssl);
$serverrandom = &Net::SSLeay::getserverrandom($ssl);
$session = &Net::SSLeay::getsession($ssl);
$masterkey = &Net::SSLeay::SESSIONgetmasterkey($session);
HHTTTTPP ((wwiitthhoouutt SS)) AAPPII
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(gethttp posthttp tcpcat
gethttpx posthttpx tcpxcat
makeheaders makeform);
($page, $result, %headers) =
= gethttp('www.bacus.pt', 443, '/protected.html',
makeheaders(Authorization =>
'Basic ' . MIME::Base64::encode("$user:$pass",''))
);
($page, $response, %replyheaders)
= posthttp('www.bacus.pt', 443, '/foo.cgi', '',
makeform(OK => '1',
name => 'Sampo'
));
($reply, $err) = tcpcat($host, $port, $request);
($page, $result, %headers) =
= gethttpx($usessl, 'www.bacus.pt', 443, '/protected.html',
makeheaders(Authorization =>
'Basic ' . MIME::Base64::encode("$user:$pass",''))
);
($page, $response, %replyheaders)
= posthttpx($usessl, 'www.bacus.pt', 443, '/foo.cgi', '',
makeform(OK => '1', name => 'Sampo' ));
($reply, $err, $servercert) = tcpxcat($usessl, $host, $port, $request);
As can be seen, the "x" family of APIs takes as first argument a flag
which indicated whether SSL is used or not.
EEXXAAMMPPLLEESS
One very good example is to look at the implementation of sslcat() in
the SSLeay.pm file.
Following is a simple SSLeay client (with too little error checking :-(
#!/usr/local/bin/perl
use Socket;
use Net::SSLeay qw(dienow dieifsslerror) ;
Net::SSLeay::loaderrorstrings();
Net::SSLeay::SSLeayaddsslalgorithms();
Net::SSLeay::randomize();
($destserv, $port, $msg) = @ARGV; # Read command line
$port = getservbyname ($port, 'tcp') unless $port =~ /^\d+$/;
$destip = gethostbyname ($destserv);
$destservparams = sockaddrin($port, $destip);
socket (S, &AFINET, &SOCKSTREAM, 0) or die "socket: $!";
connect (S, $destservparams) or die "connect: $!";
select (S); $| = 1; select (STDOUT); # Eliminate STDIO buffering
# The network connection is now open, lets fire up SSL
$ctx = Net::SSLeay::CTXnew() or dienow("Failed to create SSLCTX $!");
Net::SSLeay::CTXsetoptions($ctx, &Net::SSLeay::OPALL)
and dieifsslerror("ssl ctx set options");
$ssl = Net::SSLeay::new($ctx) or dienow("Failed to create SSL $!");
Net::SSLeay::setfd($ssl, fileno(S)); # Must use fileno
$res = Net::SSLeay::connect($ssl) and dieifsslerror("ssl connect");
print "Cipher `" . Net::SSLeay::getcipher($ssl) . "'\n";
# Exchange data
$res = Net::SSLeay::write($ssl, $msg); # Perl knows how long $msg is
dieifsslerror("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
dieifsslerror("ssl read");
print $got;
Net::SSLeay::free ($ssl); # Tear down connection
Net::SSLeay::CTXfree ($ctx);
close S;
Following is a simple SSLeay echo server (non forking):
#!/usr/local/bin/perl -w
use Socket;
use Net::SSLeay qw(dienow dieifsslerror);
Net::SSLeay::loaderrorstrings();
Net::SSLeay::SSLeayaddsslalgorithms();
Net::SSLeay::randomize();
$ourip = "\0\0\0\0"; # Bind to all interfaces
$port = 1235;
$sockaddrtemplate = 'S n a4 x8';
$ourservparams = pack ($sockaddrtemplate, &AFINET, $port, $ourip);
socket (S, &AFINET, &SOCKSTREAM, 0) or die "socket: $!";
bind (S, $ourservparams) or die "bind: $!";
listen (S, 5) or die "listen: $!";
$ctx = Net::SSLeay::CTXnew () or dienow("CTXnew ($ctx): $!");
Net::SSLeay::CTXsetoptions($ctx, &Net::SSLeay::OPALL)
and dieifsslerror("ssl ctx set options");
# Following will ask password unless private key is not encrypted
Net::SSLeay::CTXuseRSAPrivateKeyfile ($ctx, 'plain-rsa.pem',
&Net::SSLeay::FILETYPEPEM);
dieifsslerror("private key");
Net::SSLeay::CTXusecertificatefile ($ctx, 'plain-cert.pem',
&Net::SSLeay::FILETYPEPEM);
dieifsslerror("certificate");
while (1) {
print "Accepting connections...\n";
($addr = accept (NS, S)) or die "accept: $!";
select (NS); $| = 1; select (STDOUT); # Piping hot!
($af,$clientport,$clientip) = unpack($sockaddrtemplate,$addr);
@inetaddr = unpack('C4',$clientip);
print "$af connection from " .
join ('.', @inetaddr) . ":$clientport\n";
# We now have a network connection, lets fire up SSLeay...
$ssl = Net::SSLeay::new($ctx) or dienow("SSLnew ($ssl): $!");
Net::SSLeay::setfd($ssl, fileno(NS));
$err = Net::SSLeay::accept($ssl) and dieifsslerror('ssl accept');
print "Cipher `" . Net::SSLeay::getcipher($ssl) . "'\n";
# Connected. Exchange some data.
$got = Net::SSLeay::read($ssl); # Returns undef on fail
dieifsslerror("ssl read");
print "Got `$got' (" . length ($got) . " chars)\n";
Net::SSLeay::write ($ssl, uc ($got)) or die "write: $!";
dieifsslerror("ssl write");
Net::SSLeay::free ($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(dienow dieifsslerror);
Net::SSLeay::loaderrorstrings();
Net::SSLeay::SSLeayaddsslalgorithms();
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";
$ctx = Net::SSLeay::CTXnew() or dienow "CTXnew ($ctx) ($!)";
$ssl = Net::SSLeay::new($ctx) or dienow "new ($ssl) ($!)";
Net::SSLeay::setoptions($ssl, &Net::SSLeay::OPALL)
and dieifsslerror("ssl set options");
# We get already open network connection from inetd, now we just
# need to attach SSLeay to STDIN and STDOUT
Net::SSLeay::setrfd($ssl, fileno(STDIN));
Net::SSLeay::setwfd($ssl, fileno(STDOUT));
Net::SSLeay::useRSAPrivateKeyfile ($ssl, 'plain-rsa.pem',
&Net::SSLeay::FILETYPEPEM);
dieifsslerror("private key");
Net::SSLeay::usecertificatefile ($ssl, 'plain-cert.pem',
&Net::SSLeay::FILETYPEPEM);
dieifsslerror("certificate");
Net::SSLeay::accept($ssl) and dieifsslerr("ssl accept: $!");
print "Cipher `" . Net::SSLeay::getcipher($ssl) . "'\n";
$got = Net::SSLeay::read($ssl);
dieifsslerror("ssl read");
print "Got `$got' (" . length ($got) . " chars)\n";
Net::SSLeay::write ($ssl, uc($got)) or die "write: $!";
dieifsslerror("ssl write");
Net::SSLeay::free ($ssl); # Tear down the connection
Net::SSLeay::CTXfree ($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
getpage.pl - Is a utility for getting html pages from secure servers
callback.pl - Demonstrates certificate verification and callback usage
stdiobulk.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)
LLIIMMIITTAATTIIOONNSS
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 printerrs('SSLread');
$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, $written));
last if printerrs('SSLwrite');
}
Or alternatively you can just use the following convinence functions:
Net::SSLeay::sslwriteall($ssl, $message) or die "ssl write failure";
$got = Net::SSLeay::sslreadall($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 dieifsslerror is made autoloadable. If you figure out
why, drop me a line.
Callback set using SSLsetverify() does not appear to work. This may
well be eay problem (e.g. see ssl/ssllib.c line 1029). Try using
SSLCTXsetverify() 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-modssl 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
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/postfixtls/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::CTXsetoptions($ctx, &Net::SSLeay::OPALL)
and dieifsslerror("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 REMAUTOMATICALLYGENERATED109 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::sslversion = 2; # Insist on SSLv2
$Net::SSLeay::sslversion = 3; # Insist on SSLv3
$Net::SSLeay::sslversion = 10; # Insist on TLSv1
Although the autonegotiation is nice to have, the SSL standards do not
formally specify any such mechanism. Most of the world has accepted the
SSLeay/OpenSSL way of doing it as the de facto standard. But for the
few that think differently, you have to explicitly speak the correct
version. This is not really a bug, but rather a deficiency in the
standards. If a site refuses to respond or sends back some nonsensical
error codes (at SSL handshake level), try this option before mailing
me.
The high level API returns the certificate of the peer, thus allowing
one to check what certificate was supplied. However, you will only be
able to check the certificate after the fact, i.e. you already sent
your form data by the time you find out that you did not trust them,
oops.
So, while being able to know the certificate after the fact is surely
useful, the security minded would still choose to do the connection and
certificate verification first and only after that exchange data with
the site. Currently none of the high level API functions do this, thus
you would have to program it using the low level API. A good place to
start is to see how Net::SSLeay::httpcat() function is implemented.
The high level API functions use a global file handle SSLCATS
internally. This really should not be a problem because there is no way
to interleave the high level API functions, unless you use threads (but
threads are not very well supported in perl anyway (as of version
5.6.1). However, you may run into problems if you call undocumented
internal functions in an interleaved fashion.
DIAGNOSTICS "Random number generator not seeded!!!"
This warning indicates that randomize() was not able to read
/dev/random or /dev/urandom, possibly because your system does not
have them or they are differently named. You can still use SSL, but
the encryption will not be as strong.
"opentcpconnection: destination host not found:`server' (port 123)
($!)"
Name lookup for host named `server' failed.
"opentcpconnection: failed `server', 123 ($!)"
The name was resolved, but establising the TCP connection failed.
"msg 123: 1 - error:140770F8:SSL
routines:SSL23GETSERVERHELLO: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 loaderrorstrings() 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@symlabs.com)
Tel: +351-214.222.630
Fax: +351-214.222.637
VVEERRSSIIOONN
This man page documents version 1.24, released on 18.8.2003.
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 perl5.005, or 5.6.0 (or better?) though I believe it would
build with any perl5.002 or newer.
AUTHOR Originally written by Sampo Kellomaeki Maintained
by Mike McCauley and Florian Ragwitz since November 2005
COPYRIGHT Copyright (c) 1996-2003 Sampo Kellomaeki Copyright
(C) 2005 Florian Ragwitz Copyright (C) 2005 Mike
McCauley 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
./NetSSLeay/examples - Example servers and a clients
- Net::SSLeay.pm home
- Another module using OpenSSL
- OpenSSL source, documentation, etc
openssl-users-request@openssl.org - General OpenSSL mailing list
- SSL Draft specification
- HTTP specifications
- How to send password
- Entropy Gathering Daemon (EGD)
- pseudo-random number generating daemon (PRNGD)
perl(1)
perlref(1)
perllol(1)
perldoc ~openssl/doc/ssl/SSLCTXsetverify.pod
perl v5.8.8 2005-12-20 SSLeay(3)