[night1rider]

Description

wc_FreeRsaKey() returned right after the crypto callback free when the
callback returned anything other than CRYPTOCB_UNAVAILABLE. That skipped
the software cleanup, so d, p, q, dP, dQ and u could stay in
memory if the device did not wipe them.

Now the callback status is kept and the software cleanup always runs. The
function still returns the callback's status (0, or the device error). This
matches how wc_ecc_free, wc_HmacFree and wc_CmacFree already work.

Note: a callback that returns 0 no longer skips the software cleanup. A
callback that already frees the key itself (sets devId to INVALID_DEVID
and calls wc_FreeRsaKey) now gets the cleanup run twice. That is safe:
mp_forcezero/mp_clear handle already-cleared values.

Testing

• New test_wc_FreeRsaKey_CryptoCb in tests/api/test_rsa.c: device returns
  0, device returns an error, device declines, and no device. Checks the
  return value, the callback count, and that every key field is zero.
• Added a wc_FreeRsaKey(NULL) check to test_wc_InitRsaKey.
• The new test fails on the old rsa.c and passes with this change.
• unit.test --group rsa and testwolfcrypt pass with
  --enable-cryptocb --enable-cryptocbutils, on SP math, --enable-heapmath,
  and -DWOLFSSL_CHECK_MEM_ZERO.

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[github-actions]

MemBrowse Memory Report · Explore what changed →

zephyr-frdm_rw612

• FLASH: log_const_area -8 B, rodata -8 B, text +1,592 B (+0.6%, 284,040 B / 67,108,864 B, total: 0% used)

No memory changes detected for:

• gcc-arm-cortex-m0plus
• gcc-arm-cortex-m3
• gcc-arm-cortex-m4
• gcc-arm-cortex-m4-baremetal
• gcc-arm-cortex-m4-crypto-only
• gcc-arm-cortex-m4-dtls13
• gcc-arm-cortex-m4-min-ecc
• gcc-arm-cortex-m4-openssl-compat
• gcc-arm-cortex-m4-pkcs7
• gcc-arm-cortex-m4-pq
• gcc-arm-cortex-m4-rsa-only
• gcc-arm-cortex-m4-sp-math
• gcc-arm-cortex-m4-tls12
• gcc-arm-cortex-m4-tls13
• gcc-arm-cortex-m7
• gcc-arm-cortex-m7-pq
• gcc-arm-cortex-m7-tls13
• stm32-sim-stm32h753

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[Copilot]

🟢 Approval recommended

There are no active review issues for the RSA key cleanup change.

No open issues 🎉

_{Review effort: Balanced}