From a2471684dae23a676b4badea306140d24e6507f5 Mon Sep 17 00:00:00 2001 From: Lukas Wunner Date: Tue, 10 Sep 2024 16:30:27 +0200 Subject: 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 Signed-off-by: Herbert Xu --- crypto/ecdsa.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) (limited to 'crypto/ecdsa.c') diff --git a/crypto/ecdsa.c b/crypto/ecdsa.c index 6cb0a6ce9de1..cf8e0c5d1dd8 100644 --- a/crypto/ecdsa.c +++ b/crypto/ecdsa.c @@ -7,6 +7,7 @@ #include #include #include +#include #include struct ecc_ctx { @@ -169,6 +170,17 @@ static unsigned int ecdsa_key_size(struct crypto_sig *tfm) return DIV_ROUND_UP(ctx->curve->nbits, 8); } +static unsigned int ecdsa_digest_size(struct crypto_sig *tfm) +{ + /* + * ECDSA key sizes are much smaller than RSA, and thus could + * operate on (hashed) inputs that are larger than the key size. + * E.g. SHA384-hashed input used with secp256r1 based keys. + * Return the largest supported hash size (SHA512). + */ + return SHA512_DIGEST_SIZE; +} + static int ecdsa_nist_p521_init_tfm(struct crypto_sig *tfm) { struct ecc_ctx *ctx = crypto_sig_ctx(tfm); @@ -180,6 +192,7 @@ static struct sig_alg ecdsa_nist_p521 = { .verify = ecdsa_verify, .set_pub_key = ecdsa_set_pub_key, .key_size = ecdsa_key_size, + .digest_size = ecdsa_digest_size, .init = ecdsa_nist_p521_init_tfm, .exit = ecdsa_exit_tfm, .base = { @@ -202,6 +215,7 @@ static struct sig_alg ecdsa_nist_p384 = { .verify = ecdsa_verify, .set_pub_key = ecdsa_set_pub_key, .key_size = ecdsa_key_size, + .digest_size = ecdsa_digest_size, .init = ecdsa_nist_p384_init_tfm, .exit = ecdsa_exit_tfm, .base = { @@ -224,6 +238,7 @@ static struct sig_alg ecdsa_nist_p256 = { .verify = ecdsa_verify, .set_pub_key = ecdsa_set_pub_key, .key_size = ecdsa_key_size, + .digest_size = ecdsa_digest_size, .init = ecdsa_nist_p256_init_tfm, .exit = ecdsa_exit_tfm, .base = { @@ -246,6 +261,7 @@ static struct sig_alg ecdsa_nist_p192 = { .verify = ecdsa_verify, .set_pub_key = ecdsa_set_pub_key, .key_size = ecdsa_key_size, + .digest_size = ecdsa_digest_size, .init = ecdsa_nist_p192_init_tfm, .exit = ecdsa_exit_tfm, .base = { -- cgit v1.2.3