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Prevent UAF on DER objects, reject API in SNI callback#10905

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padelsbach:reject-sni-and-refcnt-der
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Prevent UAF on DER objects, reject API in SNI callback#10905
padelsbach wants to merge 1 commit into
wolfSSL:masterfrom
padelsbach:reject-sni-and-refcnt-der

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@padelsbach padelsbach commented Jul 15, 2026 •
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Description

Fixes a family of UAF due to shared DER buffer between WOLFSSL_CTX and WOLFSSL objects raised in zd 22107.

There are two situations we want to solve:

  1. Adjusting certs/keys in the SNI callback. Today this triggers a UAF, but even with a fix, does not apply the change for the active session. So this change disables those APIs.
  2. Reload certs/keys (outside of the SNI callback) on a live TLS session. Memcached and Mosquitto do this today via Openssl compat APIs (SSL_CTX_use_certificate_chain_file, SSL_CTX_use_PrivateKey_file, SSL_CTX_use_certificate)

Change is to refcount DER objects and disallow several routines from the SNI callback.

Footprint impact:

  • refcount disabled (embedded): none
  • refcount enabled w/ atomics: none (fits into padding)
  • refcount enabled w/ mutex: +56 bytes

The following APIs are not allowed during the SNI callback:

Certificate:

wolfSSL_CTX_use_certificate_file
wolfSSL_CTX_use_certificate_buffer
wolfSSL_CTX_use_certificate_ASN1
wolfSSL_CTX_use_certificate (X509)
wolfSSL_CTX_use_certificate_label (WOLF_CRYPTO_CB)
wolfSSL_CTX_use_certificate_id (WOLF_CRYPTO_CB)

Certificate chain:

wolfSSL_CTX_use_certificate_chain_file
wolfSSL_CTX_use_certificate_chain_file_format
wolfSSL_CTX_use_certificate_chain_buffer
wolfSSL_CTX_use_certificate_chain_buffer_format
wolfSSL_CTX_add_extra_chain_cert
wolfSSL_CTX_add0_chain_cert
wolfSSL_CTX_add1_chain_cert
wolfSSL_CTX_ctrl (cases SSL_CTRL_CHAIN and SSL_CTRL_EXTRA_CHAIN_CERT)

Private key:

wolfSSL_CTX_use_PrivateKey_file
wolfSSL_CTX_use_PrivateKey_buffer
wolfSSL_CTX_use_PrivateKey_ASN1
wolfSSL_CTX_use_PrivateKey (EVP_PKEY)
wolfSSL_CTX_use_RSAPrivateKey
wolfSSL_CTX_use_RSAPrivateKey_file (delegates to use_PrivateKey_file)
wolfSSL_CTX_use_PrivateKey_Id (WOLF_PRIVATE_KEY_ID)
wolfSSL_CTX_use_PrivateKey_Id_ex (delegates to _Id)
wolfSSL_CTX_use_PrivateKey_Label (WOLF_PRIVATE_KEY_ID)

Alt private key (WOLFSSL_DUAL_ALG_CERTS):

wolfSSL_CTX_use_AltPrivateKey_file
wolfSSL_CTX_use_AltPrivateKey_buffer
wolfSSL_CTX_use_AltPrivateKey_Id
wolfSSL_CTX_use_AltPrivateKey_Id_ex (delegates to _Id)
wolfSSL_CTX_use_AltPrivateKey_Label

The following APIs are not allowed while any session is active since the DH params buffer is public and thus cannot be refcounted without breaking the ABI.

DH:

wolfSSL_CTX_SetTmpDH
wolfSSL_CTX_SetTmpDH_buffer
wolfSSL_CTX_SetTmpDH_file
wolfSSL_CTX_set_tmp_dh (OpenSSL-compat, WOLFSSL_DH*)

Testing

Added unit tests.

Checklist

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

@padelsbach padelsbach force-pushed the reject-sni-and-refcnt-der branch from ef8b88b to 767782b Compare July 15, 2026 04:19
@padelsbach padelsbach force-pushed the reject-sni-and-refcnt-der branch from 767782b to c432e9e Compare July 15, 2026 13:53
@padelsbach padelsbach marked this pull request as ready for review July 15, 2026 13:54
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github-actions Bot commented Jul 15, 2026

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retest this please

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github-actions Bot commented Jul 15, 2026

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MemBrowse Memory Report

gcc-arm-cortex-m0plus

  • FLASH: .text +4 B (+0.0%, 64,187 B / 262,144 B, total: 24% used)

gcc-arm-cortex-m3

  • FLASH: .text +156 B (+0.1%, 122,661 B / 262,144 B, total: 47% used)

gcc-arm-cortex-m4

  • FLASH: .rodata.wolfSSL_ERR_reason_error_string.str1.1 +57 B, .text +192 B (+0.1%, 200,633 B / 262,144 B, total: 77% used)

gcc-arm-cortex-m4-crypto-only

  • FLASH: .text +64 B (+0.0%, 174,632 B / 262,144 B, total: 67% used)

gcc-arm-cortex-m4-dtls13

  • FLASH: .text +128 B (+0.1%, 181,080 B / 1,048,576 B, total: 17% used)

gcc-arm-cortex-m4-openssl-compat

  • FLASH: .rodata +64 B, .text +192 B (+0.0%, 771,468 B / 1,048,576 B, total: 74% used)

gcc-arm-cortex-m4-pq

  • FLASH: .rodata +56 B, .text +192 B (+0.1%, 279,708 B / 1,048,576 B, total: 27% used)

gcc-arm-cortex-m4-rsa-only

  • FLASH: .rodata +64 B, .text +192 B (+0.1%, 325,376 B / 1,048,576 B, total: 31% used)

gcc-arm-cortex-m4-tls12

  • FLASH: .text +128 B (+0.1%, 123,405 B / 262,144 B, total: 47% used)

gcc-arm-cortex-m4-tls13

  • FLASH: .rodata.wolfSSL_ERR_reason_error_string.str1.1 +57 B, .text +256 B (+0.1%, 236,459 B / 262,144 B, total: 90% used)

gcc-arm-cortex-m7

  • FLASH: .rodata.wolfSSL_ERR_reason_error_string.str1.1 +57 B, .text +192 B (+0.1%, 200,569 B / 262,144 B, total: 77% used)

gcc-arm-cortex-m7-pq

  • FLASH: .rodata +56 B, .text +192 B (+0.1%, 280,284 B / 1,048,576 B, total: 27% used)

gcc-arm-cortex-m7-tls13

  • FLASH: .rodata.wolfSSL_ERR_reason_error_string.str1.1 +57 B, .text +192 B (+0.1%, 236,459 B / 262,144 B, total: 90% used)

linuxkm-pie

  • Data: __patchable_function_entries +8 B (+0.0%, 25,568 B)

linuxkm-standard

@padelsbach padelsbach mentioned this pull request Jul 15, 2026
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@padelsbach

padelsbach commented Jul 16, 2026

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jenkins retest this please

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