linux-next/Documentation/crypto/api-sig.rst

Asymmetric Signature Algorithm Definitions
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.. kernel-doc:: include/crypto/sig.h
   :functions: sig_alg

Asymmetric Signature API
------------------------

.. kernel-doc:: include/crypto/sig.h
   :doc: Generic Public Key Signature API

.. kernel-doc:: include/crypto/sig.h
   :functions: crypto_alloc_sig crypto_free_sig crypto_sig_set_pubkey crypto_sig_set_privkey crypto_sig_keysize crypto_sig_maxsize crypto_sig_digestsize crypto_sig_sign crypto_sig_verify
crypto: sig - Introduce sig_alg backend Commit 6cb8815f41a9 ("crypto: sig - Add interface for sign/verify") began a transition of asymmetric sign/verify operations from crypto_akcipher to a new crypto_sig frontend. Internally, the crypto_sig frontend still uses akcipher_alg as backend, however: "The link between sig and akcipher is meant to be temporary. The plan is to create a new low-level API for sig and then migrate the signature code over to that from akcipher." https://lore.kernel.org/r/ZrG6w9wsb-iiLZIF@gondor.apana.org.au/ "having a separate alg for sig is definitely where we want to be since there is very little that the two types actually share." https://lore.kernel.org/r/ZrHlpz4qnre0zWJO@gondor.apana.org.au/ Take the next step of that migration and augment the crypto_sig frontend with a sig_alg backend to which all algorithms can be moved. During the migration, there will briefly be signature algorithms that are still based on crypto_akcipher, whilst others are already based on crypto_sig. Allow for that by building a fork into crypto_sig_*() API calls (i.e. crypto_sig_maxsize() and friends) such that one of the two backends is selected based on the transform's cra_type. Signed-off-by: Lukas Wunner <lukas@wunner.de> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> 2024-09-10 14:30:12 +00:00			`Asymmetric Signature Algorithm Definitions`
			`------------------------------------------`

			`.. kernel-doc:: include/crypto/sig.h`
			`:functions: sig_alg`

			`Asymmetric Signature API`
			`------------------------`

			`.. kernel-doc:: include/crypto/sig.h`
			`:doc: Generic Public Key Signature API`

			`.. kernel-doc:: include/crypto/sig.h`
crypto: ecdsa - Move X9.62 signature size calculation into template software_key_query() returns the maximum signature and digest size for a given key to user space. When it only supported RSA keys, calculating those sizes was trivial as they were always equivalent to the key size. However when ECDSA was added, the function grew somewhat complicated calculations which take the ASN.1 encoding and curve into account. This doesn't scale well and adjusting the calculations is easily forgotten when adding support for new encodings or curves. In fact, when NIST P521 support was recently added, the function was initially not amended: https://lore.kernel.org/all/b749d5ee-c3b8-4cbd-b252-7773e4536e07@linux.ibm.com/ Introduce a ->max_size() callback to struct sig_alg and take advantage of it to move the signature size calculations to ecdsa-x962.c. Introduce a ->digest_size() callback to struct sig_alg and move the maximum ECDSA digest size to ecdsa.c. It is common across ecdsa-x962.c and the upcoming ecdsa-p1363.c and thus inherited by both of them. For all other algorithms, continue using the key size as maximum signature and digest size. Signed-off-by: Lukas Wunner <lukas@wunner.de> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> 2024-09-10 14:30:27 +00:00			`:functions: crypto_alloc_sig crypto_free_sig crypto_sig_set_pubkey crypto_sig_set_privkey crypto_sig_keysize crypto_sig_maxsize crypto_sig_digestsize crypto_sig_sign crypto_sig_verify`
crypto: sig - Rename crypto_sig_maxsize() to crypto_sig_keysize() crypto_sig_maxsize() is a bit of a misnomer as it doesn't return the maximum signature size, but rather the key size. Rename it as well as all implementations of the ->max_size callback. A subsequent commit introduces a crypto_sig_maxsize() function which returns the actual maximum signature size. While at it, change the return type of crypto_sig_keysize() from int to unsigned int for consistency with crypto_akcipher_maxsize(). None of the callers checks for a negative return value and an error condition can always be indicated by returning zero. Signed-off-by: Lukas Wunner <lukas@wunner.de> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> 2024-09-10 14:30:26 +00:00