asn: verify KeyPurposeId OID bytes before setting extended key usage bits

[gasbytes]

Description

Verify a KeyPurposeId's OID bytes before mapping its wc_oid_sum() to an extended key usage bit.

Fixes zd#22337

Testing

Added a regression test that tests the behaviour with an actual id-kp-serverAuth as oid and one that must collide and check that it still doesn't allow server authentication.

Checklist

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

[Copilot]

Pull request overview

Improves EKU (Extended Key Usage) decoding safety by ensuring a KeyPurposeId’s raw OID bytes match the known OID associated with its wc_oid_sum() before mapping it to an authorization bit (preventing checksum-collision misclassification, e.g., falsely granting serverAuth).

Changes:

• Hardened DecodeExtKeyUsage() to validate OID bytes against the known OID before setting EKU bits.
• Added regression coverage (whitebox + API-level) for an OID checksum collision against id-kp-serverAuth.
• Registered the new API test in the ASN test suite header.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
wolfcrypt/src/asn.c	Adds OID-byte verification to prevent wc_oid_sum() collision from setting the wrong EKU bit.
tests/unit-mcdc/test_asn_ext_whitebox.c	Adds a whitebox regression case for a colliding OID not being treated as serverAuth.
tests/api/test_asn.h	Registers the new API regression test function in the ASN test list.
tests/api/test_asn.c	Adds an API-level regression test generating/parsing certs to validate EKU collision handling.

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[github-actions]

retest this please

[github-actions]

MemBrowse Memory Report

gcc-arm-cortex-m0plus

• FLASH: .text +36 B (+0.1%, 65,027 B / 262,144 B, total: 25% used)

gcc-arm-cortex-m3

• FLASH: .text +28 B (+0.0%, 123,839 B / 262,144 B, total: 47% used)

gcc-arm-cortex-m4-baremetal

• FLASH: .text +64 B (+0.1%, 67,619 B / 262,144 B, total: 26% used)

gcc-arm-cortex-m4-crypto-only

• FLASH: .text +64 B (+0.0%, 176,170 B / 262,144 B, total: 67% used)

gcc-arm-cortex-m4-pkcs7

• FLASH: .text +64 B (+0.0%, 215,022 B / 262,144 B, total: 82% used)

gcc-arm-cortex-m4-rsa-only

• FLASH: .text +64 B (+0.0%, 328,432 B / 1,048,576 B, total: 31% used)

gcc-arm-cortex-m4-tls13

• FLASH: .text +64 B (+0.0%, 238,753 B / 262,144 B, total: 91% used)

gcc-arm-cortex-m7-pq

• FLASH: .text +64 B (+0.0%, 298,908 B / 1,048,576 B, total: 29% used)

stm32-sim-stm32h753

• FLASH: .text +192 B (+0.1%, 186,544 B / 2,097,152 B, total: 9% used)
  No memory changes detected for:
• gcc-arm-cortex-m4
• gcc-arm-cortex-m4-dtls13
• gcc-arm-cortex-m4-min-ecc
• gcc-arm-cortex-m4-openssl-compat
• gcc-arm-cortex-m4-pq
• gcc-arm-cortex-m4-sp-math
• gcc-arm-cortex-m4-tls12
• gcc-arm-cortex-m7
• gcc-arm-cortex-m7-tls13
• linuxkm-pie
• linuxkm-standard