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Subject[PATCH v2 10/18] crypto: dh - introduce support for ephemeral key generation to dh-generic
Date
The support for NVME in-band authentication currently in the works ([1])
needs to generate ephemeral DH keys. Make dh-generic's ->set_secret()
to generate an ephemeral key via the recently added crypto_dh_gen_privkey()
in case the input ->key_size is zero. Note that this behaviour is in
analogy to ecdh's ->set_secret().

[1] https://lkml.kernel.org/r/20211122074727.25988-4-hare@suse.de

Signed-off-by: Nicolai Stange <nstange@suse.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
---
crypto/dh.c | 24 ++++++++++++++++++++----
1 file changed, 20 insertions(+), 4 deletions(-)

diff --git a/crypto/dh.c b/crypto/dh.c
index 131b80064cb1..2e49b114e038 100644
--- a/crypto/dh.c
+++ b/crypto/dh.c
@@ -71,25 +71,41 @@ static int dh_set_secret(struct crypto_kpp *tfm, const void *buf,
{
struct dh_ctx *ctx = dh_get_ctx(tfm);
struct dh params;
+ char key[CRYPTO_DH_MAX_PRIVKEY_SIZE];
+ int err;

/* Free the old MPI key if any */
dh_clear_ctx(ctx);

- if (crypto_dh_decode_key(buf, len, &params) < 0)
+ err = crypto_dh_decode_key(buf, len, &params);
+ if (err)
goto err_clear_ctx;

- if (dh_set_params(ctx, &params) < 0)
+ if (!params.key_size) {
+ err = crypto_dh_gen_privkey(params.group_id, key,
+ &params.key_size);
+ if (err)
+ goto err_clear_ctx;
+ params.key = key;
+ }
+
+ err = dh_set_params(ctx, &params);
+ if (err)
goto err_clear_ctx;

ctx->xa = mpi_read_raw_data(params.key, params.key_size);
- if (!ctx->xa)
+ if (!ctx->xa) {
+ err = -EINVAL;
goto err_clear_ctx;
+ }
+
+ memzero_explicit(key, sizeof(key));

return 0;

err_clear_ctx:
dh_clear_ctx(ctx);
- return -EINVAL;
+ return err;
}

/*
--
2.26.2
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