[kareem-wolfssl]

Description

The trailing data rejection broke this function. Trailing data check should be disabled for it as it processes one cert at a time and advances the input pointer.
If there is trailing junk, the next call will catch it.

Fixes zd#22757

Testing

Provided test case from user, as well as built in and added tests.

Checklist

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

[Copilot]

🟢 Approval recommended

No active review issues remain for the change restoring concatenated DER certificate decoding.

No open issues 🎉

What changed in this PR

Restores wolfSSL_d2i_X509 support for concatenated DER certificates by allowing trailing data while decoding one certificate and advancing the input pointer past it.

Changes:

• Enables trailing data for wolfSSL_d2i_X509 while preserving strict handling in the exact-length certificate and request APIs.
• Adds regression tests for concatenated certificates, pointer advancement, truncated input, and trailing junk.

File	Description
tests/​api/​test_ossl_x509_io.h	Declares and registers the new regression test.
tests/​api/​test_ossl_x509_io.c	Tests certificate decoding boundaries and trailing-data behavior.
src/​x509.c	Adds a trailing-data option to the shared decoder and enables it for wolfSSL_d2i_X509.

_{Review effort: Balanced}

[kareem-wolfssl]

@claude review

[claude]

I reviewed this PR and didn't find any bugs. It turns off a strict trailing-data check on a public certificate-parsing API, so a human look is still worthwhile.

What was reviewed:

• How far *in moves: derCert->length comes from AllocCopyDecodedDer(). On the template path it is capped at srcIdx, and on the non-template path at the rebounded maxIdx. Either way the pointer moves past one certificate and not past the trailing bytes.
• Who is affected: only wolfSSL_d2i_X509() gets allowTrailing=1. wolfSSL_X509_d2i(), wolfSSL_X509_d2i_ex() and wolfSSL_X509_REQ_d2i() still pass 0, and the existing CSR exemption is unchanged.
• Heap: hardcoding NULL changes nothing, because the old path through wolfSSL_X509_d2i() also passed NULL.

Extended reasoning...

The change is in src/x509.c. It adds an allowTrailing parameter to the static d2i_X509orX509REQ() helper, sets it only for the OpenSSL-compat wolfSSL_d2i_X509(), and adds a test for concatenated DER certificates. It reuses the existing DecodedCert allowTrailing bitfield, which the TRUSTED CERTIFICATE path already uses to skip the asn.c trailing-data rejection. The security-sensitive surface is X.509 DER parsing: the change relaxes the strict trailing-data check for one public API. The diff is small and follows an existing pattern, but because it loosens a parsing strictness check, I deferred instead of approving.

[github-actions]

MemBrowse Memory Report · Explore what changed →

gcc-arm-cortex-m4-openssl-compat

• FLASH: .text +64 B (+0.0%, 801,572 B / 1,048,576 B, total: 76% 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-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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