Add sanity checks in key export

[embhorn]

Description

Resolve a casting overflow condition in

1. src/ssl.c — TLS 1.2 path (line 5731)

Added a bounds check on contextLen before the seedLen calculation.

2. src/tls13.c — TLS 1.3 path (line 1027)

Added a bounds check on contextLen against UINT32_MAX

Fixes zd21242

Testing

Added test case to test_export_keying_material_cb

Checklist

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

[Copilot]

Pull request overview

This PR adds sanity checks to prevent integer overflow in key export functions by validating contextLen before casting operations.

Changes:

• Added bounds check for contextLen in TLS 1.2 key export to prevent overflow in seedLen calculation
• Added bounds check for contextLen in TLS 1.3 key export to prevent truncation when casting to word32
• Added test case to verify rejection of contextLen values exceeding UINT16_MAX

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
src/ssl.c	Added validation to reject contextLen > UINT16_MAX in TLS 1.2 path to prevent overflow
src/tls13.c	Added validation to reject contextLen > UINT32_MAX in TLS 1.3 path to prevent truncation
tests/api.c	Added test case verifying rejection of oversized contextLen values

Comments suppressed due to low confidence (1)

tests/api.c:1

• The test verifies that the function returns 0 (failure) for oversized contextLen, but there's no test coverage for the TLS 1.3 path which uses UINT32_MAX as the limit. Consider adding a test case that exercises the TLS 1.3 code path with contextLen exceeding UINT32_MAX to ensure both validation paths are covered.

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[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.

Comments suppressed due to low confidence (1)

tests/api.c:1

• The new test case claims contextLen values exceeding UINT16_MAX must be rejected, but it currently asserts success (... , 0). This makes the test contradictory and will fail to catch regressions. Update the assertion to expect a failure return (e.g., ExpectIntNE(..., 0) or compare against the project’s standard failure code for this API).

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[JacobBarthelmeh]

Jenkins retest this please.

I could not reproduce test failure locally.

bash-3.2$ ./tests/unit.test -924
starting unit tests...
 Begin API Tests
  Begin Group: ossl_dh
    924: test_wolfSSL_DH                                    : passed (  0.13234)
  End Group  : ossl_dh
 End API Tests
 Failed/Skipped/Passed/All: 0/0/1/1

[JacobBarthelmeh]

Scan-Build Analysis shows that it is waiting for status to be reported, but when I click on the link and view the test it shows as completed successfully. Run #15688 (Feb 25, 2026, 3:07:30 PM)