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Using assert() to check the length of keys and hashes included in
a certificate is not a safe approach because assert() only applies
to debug builds. A malformed certificate could exploit security
flaws in release binaries due to buffer overflows.

This patch replaces assert() with runtime checkings in the PolarSSL
authentication module, so malformed certificates can not cause a
memory overflow.

Change-Id: I42ba912020595752c806cbd242fe3c74077d993b

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

This patch implements an authentication module based on the
PolarSSL library (v1.3.9) to verify the Chain of Trust when
Trusted Boot is enabled.

PolarSSL sources must be fetched separately. The POLARSSL_DIR
build option may be used to indicate the path to the PolarSSL
main directory (this directory must contain the 'include' and
'library' subdirectories).

To be able to build PolarSSL sources as a part of the Trusted
Firmware build process, the DISABLE_PEDANTIC flag in polarssl.mk
will tell the build system to remove the -pedantic option from
the CFLAGS.

Inclusion of PolarSSL increases the memory requirements of the BL1
and BL2 images. The following are the changes made to the FVP and
Juno platforms to cater for this when TRUSTED_BOARD_BOOT is
defined:

Changes on FVP:

  - BL1 and BL2 stacks have been increased to 4 KB
  - BL1(rw) section has been increased to 32 KB.
  - BL2 memory region has been increased to 112 KB

Changes on Juno:

  - BL1 and BL2 stacks have been increased to 4 KB
  - BL1(rw) section has been increased to 32 KB.
  - Trusted ROM region in Flash has been increased to 128 KB.
  - BL2 memory region has been increased to 116 KB

Change-Id: Ie87d80d43408eb6239c4acd0ec5ab2120e4e9e80