README for the OpenSSL 0.9.8 TPM engine
Author: Kent Yoder <email@example.com>
Report bugs: firstname.lastname@example.org
This package contains 2 sets of code, a command-line utility used to
generate a TSS key blob and write it to disk and an OpenSSL engine which
interfaces with the TSS API.
Requirements: OpenSSL 0.9.8
By default, the build will assume that you have a custom openssl installed
$ configure [--enable-debug] [--with-openssl=/path/to/custom/openssl]
# make install
create_tpm_key: create a TPM key and write it to disk
usage: create_tpm_key [options] <filename>
-e|--enc-scheme encryption scheme to use [PKCSV15] or OAEP
-q|--sig-scheme signature scheme to use [DER] or SHA1
-s|--key-size key size in bits 
-a|--auth require a password for the key [NO]
-p|--popup use TSS GUI popup dialogs to get the password
for the key [NO] (implies --auth)
Key type: The TPM key type of the key created will be legacy, so that it can
be used for both signing and encryption.
Padding schemes: Choosing the encryption and signature schemes
at key creation time is mandatory because of the structure of a TPM key blob.
Once a key is created by the TPM, the encryption and signature schemes are set
in store and cannot be changed without corrupting the key (making it unloadable
into a TPM). Here are the trade-offs:
* PKCSV15 encryption scheme - all encrypted data will be padded using the
PKCSv1.5 padding algorithm. OAEP padding is considered more secure, but
many legacy apps will require PKCSv1.5 (most notably openssl). PKCSV15
padding will also allow a slightly larger chunk of data to be encrypted in
OAEP encryption scheme - all encrypted data will be padded using the OAEP
* DER signature scheme - assumes data to be signed is DER encoded (although
this is not required). Will allow signatures to be made of arbitrary
size, up to the size the padding will allow.
SHA1 signature scheme - assumes *all* data to be signed is a SHA1 hash.
This restricts the data size to be signed to 20 bytes, always.
Key sizes: Default=2048 bits. Other valid sizes are 512 and 1024 bits.
Key auth: Default=none. if -a is specified, you will be prompted on the
command line using OpenSSL for a passphrase. This passphrase is SHA1 hashed
by the TSS and used as the key's password. At key load time, you'll be
prompted for the passphrase again by OpenSSL. If -p is specified, you'll get
a GUI prompt for password.
In order to make the TPM engine prompt you for your password, add the
following code to your app:
To set the SRK password explicitly in your code, do:
ENGINE_ctrl_cmd(e, "PIN", 0, SRK_password, NULL, 0);
The default secret mode is TSS_SECRET_MODE_PLAIN, so the above code will
always work with a plaintext SRK secret. If you have the hash of your secret,
ENGINE_ctrl_cmd(e, "SECRET_MODE", TSS_SECRET_MODE_SHA1, NULL, NULL, 0);
ENGINE_ctrl_cmd(e, "PIN", 0, SRK_password_hash, NULL, 0);
To force the TSS to popup a dialog prompting you for your SRK password:
ENGINE_ctrl_cmd(e, "SECRET_MODE", TSS_SECRET_MODE_POPUP, NULL, NULL, 0);
OpenSSL TPM engine
Included in this package is a sample openssl.cnf file, which can be used
to turn on use of the TPM engine in apps where OpenSSL config support is
If there's a use case for the TPM engine that you'd like to see it support,
please drop a line to email@example.com.
Create a self-signed cert using the TPM engine:
1. Generate a TPM key and write it to a file:
$ create_tpm_key <keyfilename>
2. Make the openssl certificate request:
$ openssl req -keyform engine -engine tpm -key <keyfilename> -new -x509 -days 365 -out <certfilename>
3. Test using openssl:
$ openssl s_server -cert <certfilename> -www -accept 4433 -keyform engine -engine tpm -key <keyfilename>
$ konqueror https://localhost:4433