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limitations.md

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Limitations

  • When forking within an application it is not valid for a cryptographic operation to be started in the parent process, and completed in the child process.
  • Only one level of forking is permitted, if a child process forks again then the Intel® QAT OpenSSL* Engine will not be available in that forked process.
  • Event driven mode of polling operation is not supported in the FreeBSD Operating system or in the qatlib RPM.
  • qat_contig_mem memory driver is not supported when running under FreeBSD Operating system or in the qatlib RPM. The default is to use the USDM memory driver supplied as part of the Intel® QAT Driver.
  • Support for cipher AES-128-CBC-HMAC-SHA1 and its related ciphers was broken in release OpenSSL* 1.1.1d. This was later fixed in OpenSSL* 1.1.1e release.
  • X25519/X448 support is available only from version 4.9 of the Intel® QAT driver for Linux. Use --disable-qat_hw_ecx in the Intel® QAT OpenSSL* Engine configure when building against earlier versions of the Linux driver.
  • Support for qaeMemFreeNonZeroNUMA() USDM API is available only from version 4.10 of the Intel® QAT driver for Linux. Use --with-cc-opt="-DQAT_HW_DISABLE_NONZERO_MEMFREE" in the Intel® QAT OpenSSL* Engine configuration when building against earlier versions of the Linux driver.
  • Support for QAT HW ECX, QAT SW ECX, QAT HW PRF and QAT HW HKDF is disabled when built against OpenSSL 3.0 engine interface due to known issues, instead it uses non-accelerated implementation from OpenSSL.
  • There is known performance scaling issue (performance drop with threads >32) with ECDSA Ciphers in the QAT Software acceleration using multithread mode in the Haproxy application. This issue is not observed when using RSA ciphers or in multi-process mode.
  • There is an issue in sshd daemon application when using the QAT for default openssl. sshd looks to be closing the file descriptors associated with QAT engine and driver after initialising openssl. Work around in sshd which comments out the closefrom() calls is needed to unblock the issue.
  • SM2 ECDH and ECDSA application testing is done using BabaSSL only since OpenSSL doesn't support SMx cipher suites.
  • SM3 is disabled by default due to known issue from cryto_mb. When SM3 enabled, Performance drop observed in mulithread scenario for all ciphers suites due to the locks at engine_table_select in OpenSSL.
  • OpenSSL 1.1.1n introduced misleading error message(undefined symbol: EVP_PKEY_get_base_id) during engine load which can be ignored as it is not a real failure. This is later fixed in OpenSSL* 1.1.1o release.
  • AES-CBC-HMAC-SHA chained ciphers does not support pipeline feature when built with OpenSSL 3.0 as the corresponding support is not available in OpenSSL 3.0.
  • There is a known issue with OpenSSL s_server application using qatprovider on OpenSSL 3.0.
  • QAT Engine doesn't support ENCRYPT_THEN_MAC(default) mode of operation meaning when Encrypt then MAC is negotiated for symmetric ciphers say AES-CBC, the requests will not get offloaded via QAT_HW, instead uses OpenSSL SW. Disable ENCRYPT_THEN_MAC with the flag SSL_OP_NO_ENCRYPT_THEN_MAC programmatically using SSL_CTX_set_options() to offload symmetric chained ciphers via QAT_HW. Please note disabling ENCRYPT_THEN_MAC has security implications.