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crypto: ecdsa - Fix NIST P521 key size reported by KEYCTL_PKEY_QUERY

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When user space issues a KEYCTL_PKEY_QUERY system call for a NIST P521
key, the key_size is incorrectly reported as 528 bits instead of 521.

That's because the key size obtained through crypto_sig_keysize() is in
bytes and software_key_query() multiplies by 8 to yield the size in bits.
The underlying assumption is that the key size is always a multiple of 8.
With the recent addition of NIST P521, that's no longer the case.

Fix by returning the key_size in bits from crypto_sig_keysize() and
adjusting the calculations in software_key_query().

The ->key_size() callbacks of sig_alg algorithms now return the size in
bits, whereas the ->digest_size() and ->max_size() callbacks return the
size in bytes.  This matches with the units in struct keyctl_pkey_query.

Fixes: a7d45ba77d ("crypto: ecdsa - Register NIST P521 and extend test suite")
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
Reviewed-by: Ignat Korchagin <ignat@cloudflare.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Lukas Wunner
2025-04-07 21:32:42 +02:00
committed by Herbert Xu
parent 3828485e1c
commit 6b7f9397c9
8 changed files with 22 additions and 14 deletions
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5
crypto/ecdsa-x962.c
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@@ -82,7 +82,7 @@ static int ecdsa_x962_verify(struct crypto_sig *tfm,
int err;
sig_ctx.ndigits = DIV_ROUND_UP_POW2(crypto_sig_keysize(ctx->child),
sizeof(u64));
sizeof(u64) * BITS_PER_BYTE);
err = asn1_ber_decoder(&ecdsasignature_decoder, &sig_ctx, src, slen);
if (err < 0)
@@ -103,7 +103,8 @@ static unsigned int ecdsa_x962_max_size(struct crypto_sig *tfm)
{
struct ecdsa_x962_ctx *ctx = crypto_sig_ctx(tfm);
struct sig_alg *alg = crypto_sig_alg(ctx->child);
int slen = crypto_sig_keysize(ctx->child);
int slen = DIV_ROUND_UP_POW2(crypto_sig_keysize(ctx->child),
BITS_PER_BYTE);
/*
* Verify takes ECDSA-Sig-Value (described in RFC 5480) as input,