Request for enhancement: libspdm routine to find the hardware identity Serial Number

[lordaule]

DSP0274 documents several optional certificate extensions for hardware identity:

1. Subject Alternative Name otherName
2. SPDM Non-critical Certificate Extension

Both of these are useful for authentication:

1. in the otherName, the ub-DMTF-device-info is the "Device information string"
2. in the id-DMTF-spdm-extension, theh presence of a id-DMTF-hardware-identity can be used to "identify the hardware identity certificate", which means the certificate SerialNumber is uniquely derived from the hardware.

libspdm should export a function which scans a certificate chain looking for the hardware identity serial number, using the following logic:

• if the leaf certificate has otherName ub-DMTF-device-info, return that string.
• if any certificate in the chain has id-DMTF-spdm-extension id-DMTF-hardware-identity return the x509 serial_number of that certificate
• if none of the above are found, return nothing

[steven-bellock]

Most of these functions already exist, they just need to be exposed to Integrator.