ossh: check the key-type parse before the ID lookup

[yosuke-wolfssl]

Problem

GetOpenSshPublicKey() overwrote the result of GetStringRef() before checking it:

ret = GetStringRef(&publicKeyTypeSz, &publicKeyType, buf, len, idx);
keyId = NameToId((const char*)publicKeyType, publicKeyTypeSz);

GetStringRef() calls GetUint32(), which stores the wire length in *strSz on
success; GetStringRef()'s own bounds check (src/internal.c:4569) then fails for a
truncated key-type string and returns WS_BUFFER_E at line 4578 without ever
assigning *str. The caller's publicKeyType is an uninitialized local, so
NameToId() compared through an indeterminate pointer using a length taken from the
wire. The unchecked ret was then overwritten by the switch, so the parse failure was
reported as WS_UNIMPLEMENTED_E instead of WS_BUFFER_E.

Compiled only under WOLFSSH_TPM. The single call site is
PrepareUserAuthRequestRsa(), on the branch where the private key lives in the TPM
and only a public key blob is available — the input is the local user's public key
material, not a remote peer's. Closes f-11650.

Fix (src/ossh.c)

• NameToId() and the key-type switch run only when GetStringRef() returns
  WS_SUCCESS; that result is returned otherwise.
• publicKeyType starts NULL and keyId starts ID_UNKNOWN.

The switch body is unchanged apart from indentation. Every other GetStringRef() /
GetMpint() call in the file already gated on ret == WS_SUCCESS; this was the only
one that did not.

Tests (tests/api.c)

test_GetOpenSshPublicKey_type(), gated on WOLFSSH_TPM + WOLFSSH_TEST_INTERNAL:

Blob	Expected	idx out
"ssh" under a length of 7	WS_BUFFER_E	4
Length prefix truncated	WS_BUFFER_E	0
Empty type name	WS_UNIMPLEMENTED_E	4
ssh-dss type name, unsupported	WS_UNIMPLEMENTED_E	11
ssh-rsa + mpint e + mpint n	WS_SUCCESS	31, fully consumed

idx is asserted on the failure cases too: it keeps whatever was successfully
consumed and is not rolled back, matching every other Get* in the tree.

Runs upstream in the tpm-ssh.yml ecc/ibmswtpm2/raw cell, which builds the
check_PROGRAMs with -DWOLFSSH_TPM and runs make check TESTS=tests/api.test.

Not in this PR

• GetOpenSshPublicKey() accepts trailing bytes after a well-formed blob;
  OsshCertParse() rejects them. Pre-existing, separate hardening.
• --enable-tpm fails testsuite.test, kex.test and auth.test on master; CI runs
  only tests/api.test for that config, so it has never seen those. Pre-existing.

Verification

• --enable-tpm --enable-certs: build clean, tests/api.test passes.
• Negative control: with the src/ossh.c hunk reverted, the truncated-type case
  fails — -1017 != -1004.
• gcc-13 -O2 -Werror sweep: clean across 6 configs (enable-all, zephyr-defines,
  sftp-only, scp-only, default, smallstack).

[Copilot]

Pull request overview

Fixes TPM-only OpenSSH public-key parsing by preserving malformed key-type errors and adding regression coverage.

Changes:

• Gates key lookup on successful parsing.
• Initializes parser state safely.
• Adds malformed and valid key tests.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
tests/api.c	Adds TPM-gated regression tests.
src/ossh.c	Fixes key-type parsing and error handling.

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[wolfSSL-Fenrir-bot]

Fenrir Automated Review — PR #1193

Scan targets checked: wolfssh-bugs, wolfssh-src

Fenrir result: Approved ✅

No new issues found in the changed files.

Advisory only — this automated result does not count as a GitHub approval.