cryptocb: add AES proxy-key support and end-to-end CryptoCB AES-GCM t…

[sameehj]

…ests

Add CryptoCB-based AES proxy-key support to enable Secure Element offload without exposing raw AES key material to wolfCrypt.

This change introduces a new optional CryptoCB hook (WOLF_CRYPTO_CB_AES_SETKEY) that allows AES keys to be imported into external devices (e.g. Secure Elements or HSMs) and referenced via an opaque handle stored in aes->devCtx. When this mode is active, wolfCrypt stores only key metadata and routes AES-GCM operations through CryptoCB, bypassing software key storage and GCM table generation.

Key points:

• Add wc_CryptoCb_AesSetKey() callback for AES key import
• Update AES SetKey paths to support proxy-key mode with graceful fallback to software when CryptoCB is unavailable
• Skip GCM H/M table generation when AES-GCM is handled by the device
• Preserve existing software AES behavior when devId is INVALID_DEVID

Testing:

• Add unit test for CryptoCB AES SetKey proxy-key behavior
• Add end-to-end AES-GCM offload unit test that verifies:
  • SetKey, Encrypt, Decrypt, and Free are routed via CryptoCB
  • Correct ciphertext/auth tag generation
  • Correct plaintext recovery after decrypt
  • Proper lifecycle handling of proxy-key handles
• Tests use a mock Secure Element that internally performs software AES to validate routing without requiring hardware

This enables dual-mode operation:

• Software AES for normal builds and testing
• Secure Element–backed AES for TLS and crypto offload use cases

Description

Please describe the scope of the fix or feature addition.

Fixes zd#

Testing

How did you test?

Checklist

• added tests
• updated/added doxygen
• updated appropriate READMEs
• Updated manual and documentation

[devin-ai-integration]

🛟 Devin Lifeguard found 2 likely issues in this PR

• check-all-return-codes snippet snippet: Capture the return value of wc_CryptoCb_UnRegisterDevice() in each test (e.g., ret = wc_CryptoCb_UnRegisterDevice(TEST_CRYPTOCB_AES_DEVID); ExpectIntEQ(ret, 0);) to ensure any error is detected.
• limit-stack-usage snippet snippet: Use the WOLFSSL_SMALL_STACK pattern in the two newly added test functions: dynamically allocate the large local objects (Aes aes, the plaintext/ciphertext/authTag buffers, etc.) with XMALLOC/XFREE (guarded by #ifdef WOLFSSL_SMALL_STACK) instead of placing them on the stack.

@sameehj
please take a look at the above issues which Devin flagged. Devin will not fix these issues automatically.

[sameehj]

retest this please