TBB: build 'cert_create' with ECDSA only if OpenSSL supports it ...

Some Linux distributions include an OpenSSL library which has been
built without ECDSA support. Trying to build the certificate
generation tool on those distributions will result in a build error.

This patch fixes that issue by including ECDSA support only if
OpenSSL has been built with ECDSA. In that case, the OpenSSL
configuration file does not define the OPENSSL_NO_EC macro. The tool
will build successfully, although the resulting binary will not
support ECDSA keys.

Change-Id: I4627d1abd19eef7ad3251997d8218599187eb902

TBB: add ECDSA support to the certificate generation tool ...

This patch extends the 'cert_create' tool to support ECDSA keys
to sign the certificates. The '--key-alg' command line option
can be used to specify the key algorithm when invoking the tool.
Available options are:

    * 'rsa': create RSA-2048 keys (default option)
    * 'ecdsa': create ECDSA-SECP256R1 keys

The TF Makefile has been updated to allow the platform to specify
the key algorithm by declaring the 'KEY_ALG' variable in the
platform makefile.

The behaviour regarding key management has changed. After applying
this patch, the tool will try first to open the keys from disk. If
one key does not exist or no key is specified, and the command line
option to create keys has been specified, new keys will be created.
Otherwise an error will be generated and the tool will exit. This
way, the user may specify certain keys while the tool will create
the remaining ones. This feature is useful for testing purposes
and CI infrastructures.

The OpenSSL directory may be specified using the build option
'OPENSSL_DIR' when building the certificate generation tool.
Default is '/usr'.

Change-Id: I98bcc2bfab28dd7179f17f1177ea7a65698df4e7

TBB: use ASN.1 type DigestInfo to represent hashes ...

The cert_create tool calculates the hash of each BL image and includes
it as an ASN.1 OCTET STRING in the corresponding certificate extension.
Without additional information, the firmware running on the platform
has to know in advance the algorithm used to generate the hash.

This patch modifies the cert_create tool so the certificate extensions
that include an image hash are generated according to the following
ASN.1 structure:

    DigestInfo ::= SEQUENCE {
        digestAlgorithm  AlgorithmIdentifier,
        digest           OCTET STRING
    }

    AlgorithmIdentifier ::=  SEQUENCE  {
        algorithm        OBJECT IDENTIFIER,
        parameters       ANY DEFINED BY algorithm OPTIONAL
    }

The PolarSSL module has been updated to extract the image hash
from the certificate extension according to this structure.

Change-Id: I6d83430f12a8a0eea8447bec7c936e903f644c85

TBB: use SHA256 to generate the certificate signatures ...

This patch replaces SHA1 by SHA256 in the 'cert_create' tool, so
certificate signatures are generated according to the NSA Suite B
cryptographic algorithm requirements.

Documentation updated accordingly.

Change-Id: I7be79e6b2b62dac8dc78a4f4f5006e37686bccf6

TBB: add tool to generate certificates ...

This patch adds a tool that generates all the necessary elements
to establish the chain of trust (CoT) between the images.

The tool reads the binary images and signing keys and outputs the
corresponding certificates that will be used by the target at run
time to verify the authenticity of the images.

Note: the platform port must provide the file platform_oid.h. This
file will define the OIDs of the x509 extensions that will be added
to the certificates in order to establish the CoT.

Change-Id: I2734d6808b964a2107ab3a4805110698066a04be