On 4/18/24 11:24, Stefan Berger wrote:
ecc_is_key_valid expects a key with the most significant digit in the last entry of the digit array. Currently ecdh_set_secret passes a reversed key to ecc_is_key_valid that then passes the rather simple test checking whether the private key is in range [2, n-3]. For all current ecdh- supported curves (NIST P192/256/384) the 'n' parameter is a rather large number, therefore easily passing this test. Throughout the ecdh and ecc codebase the variable 'priv' is used for a private_key holding the bytes in proper byte order. Therefore, introduce priv in ecdh_set_secret and copy the bytes from ctx->private_key into priv in proper byte order by using ecc_swap_digits. Pass priv to ecc_is_valid_key.
Fixes: 3c4b23901a0c ("crypto: ecdh - Add ECDH software support")
Cc: Ard Biesheuvel <ardb@xxxxxxxxxx> Cc: Salvatore Benedetto <salvatore.benedetto@xxxxxxxxx> Signed-off-by: Stefan Berger <stefanb@xxxxxxxxxxxxx> Acked-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx> --- crypto/ecdh.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/crypto/ecdh.c b/crypto/ecdh.c index 3049f147e011..c02c9a2b9682 100644 --- a/crypto/ecdh.c +++ b/crypto/ecdh.c @@ -27,7 +27,9 @@ static int ecdh_set_secret(struct crypto_kpp *tfm, const void *buf, unsigned int len) { struct ecdh_ctx *ctx = ecdh_get_ctx(tfm); + u64 priv[ECC_MAX_DIGITS]; struct ecdh params; + int ret = 0;if (crypto_ecdh_decode_key(buf, len, ¶ms) < 0 ||params.key_size > sizeof(u64) * ctx->ndigits) @@ -40,13 +42,16 @@ static int ecdh_set_secret(struct crypto_kpp *tfm, const void *buf, ctx->private_key);memcpy(ctx->private_key, params.key, params.key_size);+ ecc_swap_digits(ctx->private_key, priv, ctx->ndigits);if (ecc_is_key_valid(ctx->curve_id, ctx->ndigits,- ctx->private_key, params.key_size) < 0) { + priv, params.key_size) < 0) { memzero_explicit(ctx->private_key, params.key_size); - return -EINVAL; + ret = -EINVAL; } - return 0; + memzero_explicit(priv, sizeof(priv)); + + return ret; }static int ecdh_compute_value(struct kpp_request *req)
