Module: Krypt::PEM

Defined in:
ext/krypt/core/krypt_pem.c,
ext/krypt/core/krypt_pem.c

Overview

The popular PEM format is essentially the Base64 encoding of some DER-encoded data, with additional “header” and “footer” lines indicating the type of data being encoded. The PEM module offers ways to conveniently encode and decode arbitrary PEM-formatted data.

Converting from PEM to DER

PEM-encoded data can be easily converted to equivalent DER-encoded data:

pem = File.read("data.pem")
File.open("data.der", "wb") do |f|
  f.print(Krypt::PEM.decode(pem))
end

Defined Under Namespace

Classes: PEMError

Class Method Summary collapse

Class Method Details

.Krypt::PEM.decode(data) {|der, name, i| ... } ⇒ Array

data can be either a PEM-encoded String, an IO-like object that features a read method or any arbitrary object that has a to_pem method returning either a String or an IO-like object.

Returns an Array that contains the DER-encoded results in the order they were decoded. PEM data can potentially consist of multiple elements, a common example being ‘trusted certificate bundles’ that contain a set of to-be-trusted certificates.

If additionally a block is given, block is called for each element that is decoded, where der contains the decoded element, name the identifier of the current element (e.g. ‘CERTIFICATE’) and i the index of the current element starting with 0.

Example: Decoding a simple certificate file

File.open("certificate.pem", "rb") do |f|
  cert = Krypt::PEM.decode(f)[0]
  # process the certificate
end

Example: Decoding multiple elements contained in one file

File.open("trusted-certs.pem", "rb") do |f|
  Krypt::PEM.decode(f) do |der, name, i|
    puts "Element #{i}: #{name}"
    File.open("cert-#{i}.der", "wb") do |g|
      g.print der
    end
  end
end

Yields:

  • (der, name, i)

Returns:

  • (Array) 

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# File 'ext/krypt/core/krypt_pem.c', line 99

static VALUE
krypt_pem_decode(VALUE self, VALUE pem)
{
    VALUE ary, der;
    size_t i = 0;
    int result;
    binyo_instream *in = krypt_instream_new_pem(krypt_instream_new_value_pem(pem));
    
    ary = rb_ary_new();

    while ((result = int_consume_stream(in, &der)) == KRYPT_OK) {
	if (NIL_P(der))
	    break;

	rb_ary_push(ary, der);
	if(rb_block_given_p()) {
	    uint8_t *name;
	    size_t len;
	    VALUE vname;
	    if (krypt_pem_get_last_name(in, &name, &len) == BINYO_ERR) goto error;
	    vname = rb_str_new((const char *) name, len);
	    xfree(name);
	    rb_yield_values(3, der, vname, SIZET2NUM(i++));
	}
	krypt_pem_continue_stream(in);
    }
    if (result == KRYPT_ERR) goto error;

    binyo_instream_free(in);
    return ary;

error:
    binyo_instream_free(in);
    krypt_error_raise(eKryptPEMError, "Error while decoding PEM data");
    return Qnil;
}