The 1st patch fixes a byte ordering issue where ctx->private_key is
currently passed to ecc_is_key_valid but the key is in reverse byte order.
To solve this issue it introduces the variable 'priv', that is already used
throughout the ecc and ecdh code bases for a private key in proper byte
order, and calls ecc_is_key_valid with 'priv'. Note that ecc_gen_privkey
also calls __ecc_is_key_valid with 'priv' already.
The 2nd patch gets rid of the 'priv' variable wherever it is used to hold
a private key (byte-swapped initialized from ctx->private_key) in proper
byte order and uses ctx->private_key directly that is now initialized in
proper byte order.
Regards,
Stefan
v3:
- Added Jarkko's A-b tag
- Expanded on the description of changes to ecc_gen_privkey (2/2)
v2:
- Added missing zeroizing of priv variable (1/2)
- Improved patch description (2/2)
Stefan Berger (2):
crypto: ecdh - Pass private key in proper byte order to check valid
key
crypto: ecdh & ecc - Initialize ctx->private_key in proper byte order
crypto/ecc.c | 29 ++++++++++-------------------
crypto/ecdh.c | 9 ++++++---
include/crypto/internal/ecc.h | 3 ++-
3 files changed, 18 insertions(+), 23 deletions(-)
--
2.43.0
The private key in ctx->private_key is currently initialized in reverse
byte order in ecdh_set_secret and whenever the key is needed in proper
byte order the variable priv is introduced and the bytes from
ctx->private_key are copied into priv while being byte-swapped
(ecc_swap_digits). To get rid of the unnecessary byte swapping initialize
ctx->private_key in proper byte order and clean up all functions that were
previously using priv or were called with ctx->private_key:
- ecc_gen_privkey: Directly initialize the passed ctx->private_key with
random bytes filling all the digits of the private key. Get rid of the
priv variable. This function only has ecdh_set_secret as a caller to
create NIST P192/256/384 private keys.
- crypto_ecdh_shared_secret: Called only from ecdh_compute_value with
ctx->private_key. Get rid of the priv variable and work with the passed
private_key directly.
- ecc_make_pub_key: Called only from ecdh_compute_value with
ctx->private_key. Get rid of the priv variable and work with the passed
private_key directly.
Cc: Salvatore Benedetto <[email protected]>
Signed-off-by: Stefan Berger <[email protected]>
Acked-by: Jarkko Sakkinen <[email protected]>
---
crypto/ecc.c | 29 ++++++++++-------------------
crypto/ecdh.c | 8 +++-----
include/crypto/internal/ecc.h | 3 ++-
3 files changed, 15 insertions(+), 25 deletions(-)
diff --git a/crypto/ecc.c b/crypto/ecc.c
index 2e05387b9499..c1d2e884be1e 100644
--- a/crypto/ecc.c
+++ b/crypto/ecc.c
@@ -1497,10 +1497,10 @@ EXPORT_SYMBOL(ecc_is_key_valid);
* This method generates a private key uniformly distributed in the range
* [2, n-3].
*/
-int ecc_gen_privkey(unsigned int curve_id, unsigned int ndigits, u64 *privkey)
+int ecc_gen_privkey(unsigned int curve_id, unsigned int ndigits,
+ u64 *private_key)
{
const struct ecc_curve *curve = ecc_get_curve(curve_id);
- u64 priv[ECC_MAX_DIGITS];
unsigned int nbytes = ndigits << ECC_DIGITS_TO_BYTES_SHIFT;
unsigned int nbits = vli_num_bits(curve->n, ndigits);
int err;
@@ -1509,7 +1509,7 @@ int ecc_gen_privkey(unsigned int curve_id, unsigned int ndigits, u64 *privkey)
* Step 1 & 2: check that N is included in Table 1 of FIPS 186-5,
* section 6.1.1.
*/
- if (nbits < 224 || ndigits > ARRAY_SIZE(priv))
+ if (nbits < 224)
return -EINVAL;
/*
@@ -1527,17 +1527,16 @@ int ecc_gen_privkey(unsigned int curve_id, unsigned int ndigits, u64 *privkey)
return -EFAULT;
/* Step 3: obtain N returned_bits from the DRBG. */
- err = crypto_rng_get_bytes(crypto_default_rng, (u8 *)priv, nbytes);
+ err = crypto_rng_get_bytes(crypto_default_rng,
+ (u8 *)private_key, nbytes);
crypto_put_default_rng();
if (err)
return err;
/* Step 4: make sure the private key is in the valid range. */
- if (__ecc_is_key_valid(curve, priv, ndigits))
+ if (__ecc_is_key_valid(curve, private_key, ndigits))
return -EINVAL;
- ecc_swap_digits(priv, privkey, ndigits);
-
return 0;
}
EXPORT_SYMBOL(ecc_gen_privkey);
@@ -1547,23 +1546,20 @@ int ecc_make_pub_key(unsigned int curve_id, unsigned int ndigits,
{
int ret = 0;
struct ecc_point *pk;
- u64 priv[ECC_MAX_DIGITS];
const struct ecc_curve *curve = ecc_get_curve(curve_id);
- if (!private_key || ndigits > ARRAY_SIZE(priv)) {
+ if (!private_key) {
ret = -EINVAL;
goto out;
}
- ecc_swap_digits(private_key, priv, ndigits);
-
pk = ecc_alloc_point(ndigits);
if (!pk) {
ret = -ENOMEM;
goto out;
}
- ecc_point_mult(pk, &curve->g, priv, NULL, curve, ndigits);
+ ecc_point_mult(pk, &curve->g, private_key, NULL, curve, ndigits);
/* SP800-56A rev 3 5.6.2.1.3 key check */
if (ecc_is_pubkey_valid_full(curve, pk)) {
@@ -1647,13 +1643,11 @@ int crypto_ecdh_shared_secret(unsigned int curve_id, unsigned int ndigits,
{
int ret = 0;
struct ecc_point *product, *pk;
- u64 priv[ECC_MAX_DIGITS];
u64 rand_z[ECC_MAX_DIGITS];
unsigned int nbytes;
const struct ecc_curve *curve = ecc_get_curve(curve_id);
- if (!private_key || !public_key ||
- ndigits > ARRAY_SIZE(priv) || ndigits > ARRAY_SIZE(rand_z)) {
+ if (!private_key || !public_key || ndigits > ARRAY_SIZE(rand_z)) {
ret = -EINVAL;
goto out;
}
@@ -1674,15 +1668,13 @@ int crypto_ecdh_shared_secret(unsigned int curve_id, unsigned int ndigits,
if (ret)
goto err_alloc_product;
- ecc_swap_digits(private_key, priv, ndigits);
-
product = ecc_alloc_point(ndigits);
if (!product) {
ret = -ENOMEM;
goto err_alloc_product;
}
- ecc_point_mult(product, pk, priv, rand_z, curve, ndigits);
+ ecc_point_mult(product, pk, private_key, rand_z, curve, ndigits);
if (ecc_point_is_zero(product)) {
ret = -EFAULT;
@@ -1692,7 +1684,6 @@ int crypto_ecdh_shared_secret(unsigned int curve_id, unsigned int ndigits,
ecc_swap_digits(product->x, secret, ndigits);
err_validity:
- memzero_explicit(priv, sizeof(priv));
memzero_explicit(rand_z, sizeof(rand_z));
ecc_free_point(product);
err_alloc_product:
diff --git a/crypto/ecdh.c b/crypto/ecdh.c
index c02c9a2b9682..72cfd1590156 100644
--- a/crypto/ecdh.c
+++ b/crypto/ecdh.c
@@ -27,7 +27,6 @@ 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;
@@ -41,15 +40,14 @@ static int ecdh_set_secret(struct crypto_kpp *tfm, const void *buf,
return ecc_gen_privkey(ctx->curve_id, ctx->ndigits,
ctx->private_key);
- memcpy(ctx->private_key, params.key, params.key_size);
- ecc_swap_digits(ctx->private_key, priv, ctx->ndigits);
+ ecc_digits_from_bytes(params.key, params.key_size,
+ ctx->private_key, ctx->ndigits);
if (ecc_is_key_valid(ctx->curve_id, ctx->ndigits,
- priv, params.key_size) < 0) {
+ ctx->private_key, params.key_size) < 0) {
memzero_explicit(ctx->private_key, params.key_size);
ret = -EINVAL;
}
- memzero_explicit(priv, sizeof(priv));
return ret;
}
diff --git a/include/crypto/internal/ecc.h b/include/crypto/internal/ecc.h
index 4e2f5f938e91..7ca1f463d1ec 100644
--- a/include/crypto/internal/ecc.h
+++ b/include/crypto/internal/ecc.h
@@ -103,7 +103,8 @@ int ecc_is_key_valid(unsigned int curve_id, unsigned int ndigits,
* Returns 0 if the private key was generated successfully, a negative value
* if an error occurred.
*/
-int ecc_gen_privkey(unsigned int curve_id, unsigned int ndigits, u64 *privkey);
+int ecc_gen_privkey(unsigned int curve_id, unsigned int ndigits,
+ u64 *private_key);
/**
* ecc_make_pub_key() - Compute an ECC public key
--
2.43.0
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.
Cc: Ard Biesheuvel <[email protected]>
Cc: Salvatore Benedetto <[email protected]>
Signed-off-by: Stefan Berger <[email protected]>
Acked-by: Jarkko Sakkinen <[email protected]>
---
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)
--
2.43.0
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 <[email protected]>
> Cc: Salvatore Benedetto <[email protected]>
> Signed-off-by: Stefan Berger <[email protected]>
> Acked-by: Jarkko Sakkinen <[email protected]>
> ---
> 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)