Keep out CAs from cert manager if allowed only by callback

[mattia-moffa]

Description

When an application's verify callback overrides ASN_NO_SIGNER_E or ASN_SELF_SIGNED_E on a cert, DoVerifyCallback() clears ret. ProcessPeerCerts() then reads ret==0 as proof that the CA is valid and calls AddCA() to add it to the WOLFSSL_CTX certificate manager.

Instead, the callback allowing a CA is meant to be a one-time exception, specific to that one peer (i.e. the CA shouldn't go to the CTX's cert manager permanently). This fix only adds the certificate temporarily (for this message) and then removes it from the certificate manager.

All of this is only relevant when WOLFSSL_ALT_CERT_CHAINS is not enabled, because the alt cert chains logic sets skipAddCA on an unverified cert before even doing the callback logic.

Fixes zd#22289

Testing

./configure && make && make check
./configure --enable-altcertchains && make && make check

[Copilot]

Pull request overview

This PR adjusts certificate-chain processing so that intermediate CA certificates are not added to the WOLFSSL_CTX certificate manager when they are only accepted due to an application verify-callback overriding ASN_NO_SIGNER_E or ASN_SELF_SIGNED_E. This preserves the intended “one-time exception” semantics of the callback and prevents unintended trust persistence across connections.

Changes:

• Track the pre-callback verification result (preCbRet) in ProcessPeerCerts() before invoking DoVerifyCallback().
• When the callback clears ASN_NO_SIGNER_E / ASN_SELF_SIGNED_E to success, set skipAddCA so the CA is not added to the cert manager.

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[mattia-moffa]

Jenkins retest this please

[github-actions]

MemBrowse Memory Report

gcc-arm-cortex-m3

• FLASH: .text +104 B (+0.1%, 123,911 B / 262,144 B, total: 47% used)

gcc-arm-cortex-m4

• FLASH: .text +128 B (+0.1%, 202,223 B / 262,144 B, total: 77% used)

gcc-arm-cortex-m4-dtls13

• FLASH: .text +192 B (+0.1%, 183,804 B / 1,048,576 B, total: 18% used)

gcc-arm-cortex-m4-openssl-compat

• FLASH: .text +192 B (+0.0%, 776,476 B / 1,048,576 B, total: 74% used)

gcc-arm-cortex-m4-pq

• FLASH: .text +192 B (+0.1%, 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%, 298,908 B / 1,048,576 B, total: 29% used)

gcc-arm-cortex-m7-tls13

• FLASH: .text +192 B (+0.1%, 238,881 B / 262,144 B, total: 91% used)
  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
• linuxkm-standard
• stm32-sim-stm32h753

[mattia-moffa]

Jenkins retest this please

[mattia-moffa]

Jenkins retest this please