Block cert modification in callbacks

[padelsbach]

Description

Prevent the user from modifying certificates when those buffers are aliased across WOLFSSL and WOLFSSL_CTX objects. Specifically, the wolfSSL_CTX_use_certificate* and wolfSSL_CTX_user_PrivateKey* API families (and a few other one-offs) are blocked.

This is yet another approach to solving zd 22107

Testing

New unit tests.

Checklist

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

[github-actions]

retest this please

[wolfSSL-Fenrir-bot]

Fenrir Automated Review — PR #11191

Scan targets checked: wolfcrypt-rs-bugs, wolfssl-bugs, wolfssl-src

Findings: 10
10 finding(s) posted as inline comments (see file-level comments below)

This review was generated automatically by Fenrir. Findings are non-blocking.

[wolfSSL-Fenrir-bot]

🔵 [Low] Cert-swap block is post-hoc and per-session; other sessions on the CTX keep dangling DER pointers · Use-after-free / double-free

The check runs only after the callback has already freed ctx->certificate/ctx->privateKey. In the default non-WOLFSSL_COPY_CERT build every other live WOLFSSL from that CTX still aliases the freed DerBuffer (assigned at src/internal.c:7627) and dereferences it when building its Certificate message, so the use-after-free remains reachable for concurrent sessions.

Fix: Prevent CTX cert/key replacement while sessions reference it (refcount the DerBuffers or reject the load) rather than detecting it after the free.

[padelsbach]

Refcount solution was attempted and sprawling, but would allow us to support modification in the callbacks. But too invasive of a change for an invalid use case.

[padelsbach]

The ability to reach a UAF is a legit problem with this approach. Closing the PR

[github-actions]

MemBrowse Memory Report

gcc-arm-cortex-m3

• FLASH: .text +72 B (+0.1%, 123,883 B / 262,144 B, total: 47% used)

gcc-arm-cortex-m4

• FLASH: .text +64 B (+0.0%, 202,159 B / 262,144 B, total: 77% used)

gcc-arm-cortex-m4-dtls13

• FLASH: .text +64 B (+0.0%, 183,740 B / 1,048,576 B, total: 18% used)

gcc-arm-cortex-m4-openssl-compat

• FLASH: .rodata +24 B, .text +128 B (+0.0%, 776,500 B / 1,048,576 B, total: 74% used)

gcc-arm-cortex-m4-pq

• FLASH: .text +64 B (+0.0%, 298,012 B / 1,048,576 B, total: 28% used)

gcc-arm-cortex-m4-rsa-only

• FLASH: .text +128 B (+0.0%, 328,496 B / 1,048,576 B, total: 31% used)

gcc-arm-cortex-m4-tls12

• FLASH: .text +64 B (+0.1%, 124,659 B / 262,144 B, total: 48% used)

gcc-arm-cortex-m4-tls13

• FLASH: .text +128 B (+0.1%, 238,817 B / 262,144 B, total: 91% used)

gcc-arm-cortex-m7

• FLASH: .text +64 B (+0.0%, 202,159 B / 262,144 B, total: 77% used)

gcc-arm-cortex-m7-pq

• FLASH: .text +128 B (+0.0%, 298,972 B / 1,048,576 B, total: 29% used)

gcc-arm-cortex-m7-tls13

• FLASH: .text +64 B (+0.0%, 238,817 B / 262,144 B, total: 91% used)

linuxkm-standard

• Data: __patchable_function_entries +8 B (+0.0%, 49,456 B)
  No memory changes detected for:
• gcc-arm-cortex-m0plus
• gcc-arm-cortex-m4-baremetal
• gcc-arm-cortex-m4-crypto-only
• gcc-arm-cortex-m4-min-ecc
• gcc-arm-cortex-m4-pkcs7
• gcc-arm-cortex-m4-sp-math
• linuxkm-pie
• stm32-sim-stm32h753

[padelsbach]

Superseded by #11203