EVP_MAC-CMAC(7ossl)

📦 version 3.5.0, in opensuse-leap 16.0

💅 EVP_MAC-CMAC — the CMAC EVP_MAC implementation ✨

okay so this is a page from the OpenSSL manual set (manual name 7ossl, iykyk), and it's literally all about the CMAC implementation that lives inside the EVP_MAC API. no cap, it's a good one. 🎀

✨ NAME ✨

EVP_MAC-CMAC — the CMAC EVP_MAC implementation, bestie. that's the whole name. short, sweet, iconic. 👑

🌸 DESCRIPTION 🌸

So basically, this is support for computing CMAC MACs through the EVP_MAC API. 💖

And the way it works? This implementation uses EVP_CIPHER functions to get access to the underlying cipher. it's giving "small implementation, big cipher energy." 🦋

🧚 Identity

This implementation is identified with this name and properties, to be used with EVP_MAC_fetch():

"CMAC", "provider=default" or "provider=fips"

like, that's its whole government name. the "CMAC" part, plus either "provider=default" or "provider=fips" in the properties. slay. ✨

🔥 Supported parameters

The general description of these parameters can be found in "PARAMETERS" in EVP_MAC(3). go read that if you want the full lore.

The following parameter can be set with EVP_MAC_CTX_set_params():

  • "key" (OSSL_MAC_PARAM_KEY) <octet string> — Sets the MAC key. Setting this parameter is identical to passing a key to EVP_MAC_init(3). so like, either way you're getting the key in there, same vibe. 🔑
  • "cipher" (OSSL_MAC_PARAM_CIPHER) <UTF8 string> — Sets the name of the underlying cipher to be used. and bestie, hear me: the mode of the cipher must be CBC. not optional. CBC or bust. 💅
  • "properties" (OSSL_MAC_PARAM_PROPERTIES) <UTF8 string> — Sets the properties to be queried when trying to fetch the underlying cipher. This must be given together with the cipher naming parameter to be considered valid. they're a package deal, fr fr. 🫶
  • "encrypt-check" (OSSL_CIPHER_PARAM_FIPS_ENCRYPT_CHECK) <integer> — This option is used by the OpenSSL FIPS provider. If required this parameter should be set before EVP_MAC_init(). The default value of 1 causes an error when a unapproved Triple-DES encryption operation is triggered. Setting this to 0 will ignore the error and set the approved "fips-indicator" to 0. This option breaks FIPS compliance if it causes the approved "fips-indicator" to return 0. 😭 so like... yes it silences the error, but it's lowkey snitching on yourself compliance-wise. be careful.
⚠️ real talk: that last bit genuinely matters — flipping "encrypt-check" to 0 can break FIPS compliance. not a vibe to do casually.

The following parameters can be retrieved with EVP_MAC_CTX_get_params():

  • "size" (OSSL_MAC_PARAM_SIZE) <unsigned integer> — The "size" parameter can also be retrieved with with EVP_MAC_CTX_get_mac_size(). The length of the "size" parameter is equal to that of an unsigned int. (yes, the original says "with with" — I'm not fixing it, facts are facts 💀)
  • "block-size" (OSSL_MAC_PARAM_BLOCK_SIZE) <unsigned integer> — Gets the MAC block size. The "block-size" parameter can also be retrieved with EVP_MAC_CTX_get_block_size(). two ways in, same answer. 🎀
  • "fips-indicator" (OSSL_CIPHER_PARAM_FIPS_APPROVED_INDICATOR) <integer> — This option is used by the OpenSSL FIPS provider. A getter that returns 1 if the operation is FIPS approved, or 0 otherwise. This may be used after calling EVP_MAC_final(). It may return 0 if the "encrypt-check" option is set to 0. 👀 so yeah, that getter is how you check whether you're still in the approved club.

🦋 SEE ALSO 🦋

go click around, it's a whole interconnected universe out there. 🌈

Copyright 2018-2024 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at <https://www.openssl.org/source/license.html>.

and that's the whole page, bestie — no notes, 10/10, she ate. 💖✨

version 3.5.0, dated 2026-09-25, manual EVP_MAC-CMAC(7ossl) — mwah, go forth and MAC responsibly 🫶🎀

📦 where this page comes from