Bound keywrap client requests against the comm data buffer

[yosuke-wolfssl]

Problem

The five keywrap/data-wrap client request builders validated the caller-supplied
length only against WOLFHSM_CFG_KEYWRAP_MAX_KEY_SIZE / _MAX_DATA_SIZE
(default 2000), then assembled the request directly in the comm data buffer,
which holds WOLFHSM_CFG_COMM_DATA_LEN bytes (default 1280). A maximum-sized
key wrap copied 6 + 32 + 2000 = 2038 bytes into that 1280-byte region, running
off the end of whCommClient.packet[] and over the adjacent transport context
pointers. wh_CommClient_SendRequest does reject an over-long data_size, but
only after the copy has already happened. Reachable from every public blocking
wrapper; no existing test used a key large enough to cross the boundary.

Fix (src/wh_client_keywrap.c)

• Each builder now rejects the full wire length before any copy:
  sizeof(*req) [+ sizeof(*metadata)] + payloadSz > WOLFHSM_CFG_COMM_DATA_LEN
  returns WH_ERROR_BADARGS, matching the existing wh_Client_KeyCacheRequest_ex
  pattern.
• wh_message_keystore.h static-asserts, per request type, that the
  configured maximum plus its header fits the comm data buffer, so an explicit
  over-large setting fails the build instead of overflowing at runtime.
• wh_settings.h derives the two maximums from WOLFHSM_CFG_COMM_DATA_LEN
  when 2000 will not fit, so keywrap builds out of the box. The defaults also
  moved next to WOLFHSM_CFG_COMM_DATA_LEN; they previously sat in a block
  skipped under WH_PADDING_CHECK, where the wire-format audit could not see
  them.

The server side needed no change — its handlers already bound every copy with
reqDataSz / respDataSz.

Closes f-7150.

Behavior change

WOLFHSM_CFG_COMM_DATA_LEN	Keywrap max (was)	Keywrap max (now)
1280 (default)	2000	1240
8192 (all in-tree configs)	2000	2000

Requests of 1240–2000 bytes on a default-sized comm buffer now return
WH_ERROR_BADARGS. They were never serviceable — they overran the buffer.
Integrators needing the full 2000 bytes should raise WOLFHSM_CFG_COMM_DATA_LEN
to at least 2040.

Tests

_whTest_KeywrapOversizeRequest in test-refactor/client-server/wh_test_keywrap.c
drives all five public wrappers one byte past the configured maximum and requires
WH_ERROR_BADARGS. The input buffer is deliberately small, so a builder that
copied before checking trips ASan.

Verification

• test-refactor: 43 passed, 26 skipped, 0 failed of 69. Legacy test/ and both
  POSIX examples build clean under -Werror.
• Negative controls: reverting the runtime check reproduces
  AddressSanitizer: stack-buffer-overflow ... in wh_Client_KeyWrapRequest; an
  explicit MAX_KEY_SIZE 2000 at COMM_DATA_LEN 1280 fails the build on the
  static asserts; a default config with only WOLFHSM_CFG_KEYWRAP set compiles
  and derives 1240.

[Copilot]

Pull request overview

This pull request fixes a client-side buffer overflow in the keywrap/data-wrap request builders by ensuring the full on-wire request length is validated against the comm data buffer size before any payload is copied into whCommClient.packet[]. It also makes configuration safer by deriving keywrap max payload sizes from WOLFHSM_CFG_COMM_DATA_LEN when needed and adding compile-time assertions to prevent unsafe explicit configurations.

Changes:

• Add pre-copy request size bounds checks in all five keywrap/data-wrap client request builders.
• Add compile-time static asserts to guarantee “max payload + header” fits within WOLFHSM_CFG_COMM_DATA_LEN, and derive default keywrap max sizes from the comm buffer size when 2000 won’t fit.
• Add a regression test ensuring oversize payloads are rejected before any copy (ASan-negative-control friendly), and update configuration documentation.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
wolfhsm/wh_settings.h	Derives keywrap max sizes from comm buffer length and defines request-overhead constant for safe defaults.
wolfhsm/wh_message_keystore.h	Adds compile-time static asserts ensuring keywrap requests fit in the comm data buffer.
src/wh_client_keywrap.c	Rejects oversize keywrap/data-wrap requests before copying into the comm data buffer.
test-refactor/client-server/wh_test_keywrap.c	Adds an oversize-request regression test across all five public wrappers.
docs/src/9-Configuration.md	Documents derived defaults and build-time failure behavior for invalid max-size configurations.

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[wolfSSL-Fenrir-bot]

Fenrir Automated Review — PR #494

Scan targets checked: wolfhsm-core-bugs, wolfhsm-crypto-bugs, wolfhsm-src

No new issues found in the changed files. ✅