Provided by: libconvert-pem-perl_0.08-2_all 
NAME
Convert::PEM - Read/write encrypted ASN.1 PEM files
SYNOPSIS
use Convert::PEM;
my $pem = Convert::PEM->new(
Name => "DSA PRIVATE KEY",
ASN => qq(
DSAPrivateKey SEQUENCE {
version INTEGER,
p INTEGER,
q INTEGER,
g INTEGER,
pub_key INTEGER,
priv_key INTEGER
}
));
my $keyfile = 'private-key.pem';
my $pwd = 'foobar';
my $pkey = $pem->read(
Filename => $keyfile,
Password => $pwd
);
$pem->write(
Content => $pkey,
Password => $pwd,
Filename => $keyfile
);
DESCRIPTION
Convert::PEM reads and writes PEM files containing ASN.1-encoded objects. The files can
optionally be encrypted using a symmetric cipher algorithm, such as 3DES. An unencrypted
PEM file might look something like this:
-----BEGIN DH PARAMETERS-----
MB4CGQDUoLoCULb9LsYm5+/WN992xxbiLQlEuIsCAQM=
-----END DH PARAMETERS-----
The string beginning "MB4C..." is the Base64-encoded, ASN.1-encoded "object."
An encrypted file would have headers describing the type of encryption used, and the
initialization vector:
-----BEGIN DH PARAMETERS-----
Proc-Type: 4,ENCRYPTED
DEK-Info: DES-EDE3-CBC,C814158661DC1449
AFAZFbnQNrGjZJ/ZemdVSoZa3HWujxZuvBHzHNoesxeyqqidFvnydA==
-----END DH PARAMETERS-----
The two headers ("Proc-Type" and "DEK-Info") indicate information about the type of
encryption used, and the string starting with "AFAZ..." is the Base64-encoded, encrypted,
ASN.1-encoded contents of this "object."
The initialization vector ("C814158661DC1449") is chosen randomly.
USAGE
$pem = Convert::PEM->new( %arg )
Constructs a new Convert::PEM object designed to read/write an object of a specific type
(given in %arg, see below). Returns the new object on success, "undef" on failure (see
ERROR HANDLING for details).
%arg can contain:
• Name
The name of the object; when decoding a PEM-encoded stream, the name in the encoding
will be checked against the value of Name. Similarly, when encoding an object, the
value of Name will be used as the name of the object in the PEM-encoded content. For
example, given the string "FOO BAR", the output from encode will start with a header
like:
-----BEGIN FOO BAR-----
Name is a required argument.
• ASN
An ASN.1 description of the content to be either encoded or decoded.
ASN is a required argument.
• Macro
If your ASN.1 description (in the ASN parameter) includes more than one ASN.1 macro
definition, you will want to use the Macro parameter to specify which definition to
use when encoding/decoding objects. For example, if your ASN.1 description looks like
this:
Foo ::= SEQUENCE {
x INTEGER,
bar Bar
}
Bar ::= INTEGER
If you want to encode/decode a "Foo" object, you will need to tell Convert::PEM to use
the "Foo" macro definition by using the Macro parameter and setting the value to
"Foo".
Macro is an optional argument.
$obj = $pem->decode(%args)
Decodes, and, optionally, decrypts a PEM file, returning the object as decoded by
Convert::ASN1. The difference between this method and read is that read reads the contents
of a PEM file on disk; this method expects you to pass the PEM contents as an argument.
If an error occurs while reading the file or decrypting/decoding the contents, the
function returns undef, and you should check the error message using the errstr method
(below).
%args can contain:
• Content
The PEM contents.
• Password
The password with which the file contents were encrypted.
If the file is encrypted, this is a mandatory argument (well, it's not strictly
mandatory, but decryption isn't going to work without it). Otherwise it's not
necessary.
$blob = $pem->encode(%args)
Constructs the contents for the PEM file from an object: ASN.1-encodes the object,
optionally encrypts those contents.
Returns undef on failure (encryption failure, file-writing failure, etc.); in this case
you should check the error message using the errstr method (below). On success returns the
constructed PEM string.
%args can contain:
• Content
A hash reference that will be passed to Convert::ASN1::encode, and which should
correspond to the ASN.1 description you gave to the new method. The hash reference
should have the exact same format as that returned from the read method.
This argument is mandatory.
• Password
A password used to encrypt the contents of the PEM file. This is an optional argument;
if not provided the contents will be unencrypted.
$obj = $pem->read(%args)
Reads, decodes, and, optionally, decrypts a PEM file, returning the object as decoded by
Convert::ASN1. This is implemented as a wrapper around decode, with the bonus of reading
the PEM file from disk for you.
If an error occurs while reading the file or decrypting/decoding the contents, the
function returns undef, and you should check the error message using the errstr method
(below).
In addition to the arguments that can be passed to the decode method (minus the Content
method), %args can contain:
• Filename
The location of the PEM file that you wish to read.
$pem->write(%args)
Constructs the contents for the PEM file from an object: ASN.1-encodes the object,
optionally encrypts those contents; then writes the file to disk. This is implemented as a
wrapper around encode, with the bonus of writing the file to disk for you.
Returns undef on failure (encryption failure, file-writing failure, etc.); in this case
you should check the error message using the errstr method (below). On success returns the
constructed PEM string.
In addition to the arguments for encode, %args can contain:
• Filename
The location on disk where you'd like the PEM file written.
$pem->errstr
Returns the value of the last error that occurred. This should only be considered
meaningful when you've received undef from one of the functions above; in all other cases
its relevance is undefined.
$pem->asn
Returns the Convert::ASN1 object used internally to decode and encode ASN.1
representations. This is useful when you wish to interact directly with that object; for
example, if you need to call configure on that object to set the type of big-integer class
to be used when decoding/encoding big integers:
$pem->asn->configure( decode => { bigint => 'Math::Pari' },
encode => { bigint => 'Math::Pari' } );
ERROR HANDLING
If an error occurs in any of the above methods, the method will return "undef". You should
then call the method errstr to determine the source of the error:
$pem->errstr
In the case that you do not yet have a Convert::PEM object (that is, if an error occurs
while creating a Convert::PEM object), the error can be obtained as a class method:
Convert::PEM->errstr
For example, if you try to decode an encrypted object, and you do not give a passphrase to
decrypt the object:
my $obj = $pem->read( Filename => "encrypted.pem" )
or die "Decryption failed: ", $pem->errstr;
LICENSE
Convert::PEM is free software; you may redistribute it and/or modify it under the same
terms as Perl itself.
AUTHOR & COPYRIGHTS
Except where otherwise noted, Convert::PEM is Copyright Benjamin Trott,
cpan@stupidfool.org. All rights reserved.