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Peter Parker wrote:
Dave,
Thank you for the quick and thorough response. This is good stuff.
Yes, so the files I will be encrypting will be over 100 bytes. I
am aware of the key size requirements - 1028 was only used as a
placeholder for the example commands I provided. Does this mean
that I will be able to use RSA or not?
You lost me with the chaining and AKI stuff. I have no idea what
either of those mean. Does the CMS approach that you suggested
address this issue? In either case, I like the idea of using CMS.
The major reason that I am using the x509 (or originally the ca)
utility is that I want to be able to set begin and end valid dates
(-startdate, -enddate) for the
public and private keys and create certificates as well. I also
want to associate some metadata with them like organization and
locality, for that I am currently using the -subj command.
Am I correct that the large PEM file includes both a public and
private key? If so I should be able to extract them from the PEM
and then use something (rsautl, enc or ...) to encrypt and decrypt
the files. After successfully extracting what I understand to be a
public key from the PEM, I receive this error from the rsautl
utility: "unable to load Public Key. Error in rsautl"
Without going into the ins and outs of using the openssl utility,
you can actually infer a lot from the output PEM files themselves.
They are text files with the certificate parts and key parts base64
encoded and bookended by
-----BEGIN CERTIFICATE-----
...
-----END CERTIFICATE-----
for certificates in which case you can use 'openssl x509
<arguments>' to inspect them, run "openssl x509 -help" for the
options in this case.
AND
-----BEGIN RSA PRIVATE KEY-----
...
-----END RSA PRIVATE KEY-----
for a key (but notice this key is actually an RSA key, you can have
other types of keys so this text may be something like 'BEGIN
<other type> PRIVATE KEY'). The RSA keyword gives you the clue
to use 'openssl rsa <args>' to inspect this one, try 'openssl
rsa -help' to see what is available. You should also know the
password for the private key or you will be told zip by 'openssl
rsa'. The private key should be passworded, but you can strip the
password from them, which is not recommended but procedurally easier
in some circumstances beyond this discussion.
Also note that some certificates may or may not include a key in the
output file, if they don't you will have a separate key file. But
just looking at the certificate or key file and the bookends of the
base64 encoded part will tell you which file contains what.
Could you give me some examples of how you would use CMS or, just
use these utilities properly, to achieve what I'm trying to do.
I really appreciate your help.
Thanks,
Peter
On Tue, Nov 20, 2012 at 10:17 PM, Dave Thompson <dthomp...@prinpay.com> wrote:
>From: owner-openssl-us...@openssl.org
On Behalf Of Peter Parker
>Sent: Tuesday, 20 November, 2012 20:59
>Subject: This is one for the Pros
Not really. This is pretty basic.
>I've been trying to generate a public/private key pair
after
>generating the certificates, but OpenSSL keeps giving me
an error.
>The commands and the error are below. Thanks.
No you're not; you're generating a CA keypair and cert
(directly),
then an application keypair, then an application cert (via
CSR).
Which is the (well, a) correct sequence, for one entity.
>Commands
>#openssl req -new -x509 -extensions v3_ca -days 365
-keyout caKey.pem
>-passout pass:test -out caCert.crt -batch
>#openssl genrsa -out application.pem -passout pass:test
-des3 1028
1028 is an unusual size for an RSA key; most folks use
power-of-2
based values like 1024 1536 2048. 1024 is presently rather
marginal
for security; for example, NIST has it deprecated since the
end of
2010, and prohibited after the end of 2013, for US government
use.
>#openssl req -new -key application.pem -passin pass:test
-out
application.csr -batch
A second req -new -batch generates a CSR with the same DN ...
>#openssl x509 -req -days 365 -in application.csr -CA
caCert.crt
-CAcreateserial
>-CAkey caKey.pem -passin:test -out test-key.pem
-extensions ssl_cert
... thus this creates a CA-signed cert which appears to be
self-signed,
and will not chain correctly with OpenSSL. If the ssl_cert
section of your
config file (which doesn't exist in the distro file) includes
AKI, other
software that chains primarily by AKI may work, but this is
still incorrect.
This puts the cert in a file named test-key.pem, which is a
misleading name.
>#openssl rsa -in test-key.pem -passin pass:test -out
pub-key.pem -outform
PEM -pubout
And therefore this command, which is not the last one, fails
because
you told it to read the privatekey from a file which is a
certificate.
application.pem is your privatekey.
>#openssl rsautl -encrypt -inkey pub-key.pem -pubin -in
testfile.txt -out
eFile.ssl
>Error
>"unable to load Private Key" (I receive this after the
last command)
Not last.
>The key thing that I am trying to do is to encrypt some
files with the key
>that I generate. I do however want to use the public and
private keys that
>I get out of the PEM file using the x509 (or the ca
utilities).
If (any of) your files are larger than about 100 bytes (for
1024-bit RSA)
you can't use raw RSA; even if they aren't, you can't
interoperate with
properly designed software that doesn't use raw RSA. The
conventional
approach is to encrypt the "bulk" data symmetrically with a
nonce key (DEK)
and PK (RSA) encrypt that DEK; there are numerous schemes that
do this,
but the one that OpenSSL supports directly is PKCS7/CMS/SMIME.
(CMS is an
updated Internet version of PKCS7, and SMIME is a simple
wrapping of CMS.)
You can generate and use RSA keys without using certificates
(and without
using the req x509 ca utilities) IF you have a way to
"distribute" them
correctly -- that is, to make sure the "enveloper" always uses
a correct
publickey for the recipient and not a forged, tampered, or
obsolete one.
(And similarly the verifier for a signer.) Most standard
schemes do use
X.509 certs for this purpose, because they are also standard.
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