Fix 32bit struct serialization

[seanjin99]

Problem Summary
The SecAPI3 reference implementation uses a client-TA (Trusted Application) serialization protocol where data structures are passed between the client library and the TA. These structures use fixed 64-bit fields (uint64_t) for wire compatibility, but the internal TA code uses platform-native size_t fields. On 64-bit platforms, both are 8 bytes, so no conversion is needed. On 32-bit platforms, size_t is 4 bytes, causing struct size mismatches that corrupt data.

Root Cause Analysis
The SecAPI3 defines paired struct types:

Wire format (*_s suffix): Uses uint64_t fields for consistent size across platforms
Internal format: Uses size_t fields for native pointer arithmetic

Struct	Wire Format (32-bit)	Internal Format (32-bit)	Mismatch
sa_unwrap_parameters_ec_elgamal_s	16 bytes (2×uint64_t)	N/A	N/A
sa_unwrap_parameters_ec_elgamal	N/A	8 bytes (2×size_t)	8 bytes
sa_subsample_length_s	16 bytes (2×uint64_t)	N/A	N/A
sa_subsample_length	N/A	8 bytes (2×size_t)	8 bytes

Bug 1: EC ElGamal Key Unwrap (ta.c:607-612)
Before (broken on 32-bit):
memcpy(&parameters_ec_elgamal, params[2].mem_ref, params[2].mem_ref_size);
algorithm_parameters = params[2].mem_ref;
The client sends sa_unwrap_parameters_ec_elgamal_s (16 bytes), but the code copies into sa_unwrap_parameters_ec_elgamal (8 bytes on 32-bit). This causes:
Buffer overflow writing 16 bytes into 8-byte struct
Misaligned field reads (offset reads key_length's upper 32 bits)

After fixed:
memcpy(&parameters_ec_elgamal_s, params[2].mem_ref, params[2].mem_ref_size);
parameters_ec_elgamal.offset = (size_t)parameters_ec_elgamal_s.offset;
parameters_ec_elgamal.key_length = (size_t)parameters_ec_elgamal_s.key_length;
algorithm_parameters = &parameters_ec_elgamal;

Bug 2: CENC Size Validation (ta.c:1830)
Before (broken on 32-bit):
if (params[1].mem_ref_size != sizeof(sa_subsample_length) * sample.subsample_count)
The client sends sa_subsample_length_s array (16 bytes/entry), but validation expects sa_subsample_length (8 bytes/entry on 32-bit). Every CENC request fails validation.

After fixed:
if (params[1].mem_ref_size != sizeof(sa_subsample_length_s) * sample.subsample_count)

Bug 3: CENC Client Serialization (sa_process_common_encryption.c:120)
Before (broken on 32-bit):
Client sends original array (wrong struct type)
CREATE_PARAM(param1, samples[i].subsample_lengths, param1_size);
After fixed:
Client sends converted array with fixed-size fields
CREATE_PARAM(param1, subsample_length_s, param1_size);

Impact: Fixes 516 CENC "integer overflow" errors caused by TA reading misaligned data on 32 bits platform.

Platform	Before	After
macOS 64-bit (ENABLE_SVP=ON)	6678 PASSED	6678 PASSED
ARM32 embedded device	586 FAILED	All PASSED

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