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SE050: keep Binary ECDH derive target on pre-7.2 middleware

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Real SE050 hardware (applet 3.1.1, JCOP4) refuses ReadObject on a
symmetric key object created without a read policy just like applet 7.2
does, and pre-7.2 middleware has no way to grant that policy:
sss_policy_common_u can_Read maps to POLICY_OBJ_ALLOW_READ only for
SSS_HAVE_SE05X_VER_GTE_07_02 builds and the symmetric key policy union
has no read flag at all. Switching the derive target to an HMACKey
object unconditionally therefore broke ECDH offload on applet 3.x parts
with SW 0x6986 at the shared secret export.

Restrict the HMACKey target and its attached read policy to
SSS_HAVE_SE05X_VER_GTE_07_02 builds and restore the original Binary
object flow otherwise: no pre-created target, erase before derive, and
the middleware creates the object when storing the derived secret.
Binary objects are readable without an attached policy.

Verified on SE050C (applet 3.1.1) hardware: the ECC and CURVE25519
wolfCrypt tests fail with SW 0x6986 without this change and pass with
it, matching master behavior on the same part. The applet 7.2 path is
unchanged.
This commit is contained in:
Andrew Hutchings
2026-08-03 16:34:07 +01:00
parent 4c055f5272
commit 50bb36d3bc
1 changed files with 40 additions and 16 deletions
Download Patch File Download Diff File Expand all files Collapse all files
wolfcrypt/src/port/nxp/se050_port.c
+40 -16
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@@ -2850,16 +2850,23 @@ int se050_ecc_shared_secret(ecc_key* private_key, ecc_key* public_key,
status = sss_key_object_allocate_handle(&deriveKey,
keyIdAes,
kSSS_KeyPart_Default,
#if defined(SSS_HAVE_SE05X_VER_GTE_07_02) && SSS_HAVE_SE05X_VER_GTE_07_02
kSSS_CipherType_HMAC,
#else
/* The applet denies ReadObject on a symmetric key object
* created without a read policy, and pre-7.2 middleware has
* no way to grant one, so keep the Binary derive target
* which ReadObject allows by default */
kSSS_CipherType_Binary,
#endif
keySize,
kKeyObject_Mode_Transient);
}
#if defined(SSS_HAVE_SE05X_VER_GTE_07_02) && SSS_HAVE_SE05X_VER_GTE_07_02
if (status == kStatus_SSS_Success) {
byte keyBuf[MAX_ECC_BYTES];
#if defined(SSS_HAVE_SE05X_VER_GTE_07_02) && SSS_HAVE_SE05X_VER_GTE_07_02
sss_policy_u commonPol;
sss_policy_t derivePolicy;
#endif
/* Try to delete existing key first, ignore return since will
* fail if no key exists yet */
@@ -2870,8 +2877,7 @@ int se050_ecc_shared_secret(ecc_key* private_key, ecc_key* public_key,
* secret exactly, so the object must be created before the
* derive (returns SW 0x6985 otherwise) */
XMEMSET(keyBuf, 0, sizeof(keyBuf));
#if defined(SSS_HAVE_SE05X_VER_GTE_07_02) && SSS_HAVE_SE05X_VER_GTE_07_02
/* Applet 7.2 denies ReadObject on a symmetric key object created
/* The applet denies ReadObject on a symmetric key object created
* with no policy attached (SW 0x6986), so the derived secret
* could not be exported. Attach a policy allowing the host to
* read the secret back, overwrite the object and delete it; an
@@ -2889,28 +2895,34 @@ int se050_ecc_shared_secret(ecc_key* private_key, ecc_key* public_key,
status = sss_key_store_set_key(&host_keystore, &deriveKey,
keyBuf, keySize, keySize * 8, &derivePolicy,
sizeof(derivePolicy));
#else
status = sss_key_store_set_key(&host_keystore, &deriveKey,
keyBuf, keySize, keySize * 8, NULL, 0);
#endif
if (status == kStatus_SSS_Success) {
deriveKeyCreated = 1;
}
}
#endif
if (status == kStatus_SSS_Success) {
status = sss_derive_key_context_init(&ctx_derive_key, cfg_se050_i2c_pi,
&ref_private_key, kAlgorithm_SSS_ECDH,
kMode_SSS_ComputeSharedSecret);
if (status == kStatus_SSS_Success) {
#if !(defined(SSS_HAVE_SE05X_VER_GTE_07_02) && SSS_HAVE_SE05X_VER_GTE_07_02)
/* Try to delete existing key first, ignore return since will
* fail if no key exists yet */
sss_key_store_erase_key(&host_keystore, &deriveKey);
#endif
status = sss_derive_key_dh(&ctx_derive_key, &ref_public_key,
&deriveKey);
}
if (status == kStatus_SSS_Success) {
size_t outlenSz = (size_t)*outlen;
size_t outlenSzBits = outlenSz * 8;
#if defined(SSS_HAVE_SE05X_VER_GTE_07_02) && SSS_HAVE_SE05X_VER_GTE_07_02
/* sss_key_store_get_key has no HMAC read case, so read the
* object back as AES type (both are a plain ReadObject) */
deriveKey.cipherType = kSSS_CipherType_AES;
#else
deriveKeyCreated = 1;
#endif
/* derived key export */
status = sss_key_store_get_key(&host_keystore, &deriveKey,
out, &outlenSz, &outlenSzBits);
@@ -3486,16 +3498,23 @@ int se050_curve25519_shared_secret(curve25519_key* private_key,
status = sss_key_object_allocate_handle(&deriveKey,
keyIdAes,
kSSS_KeyPart_Default,
#if defined(SSS_HAVE_SE05X_VER_GTE_07_02) && SSS_HAVE_SE05X_VER_GTE_07_02
kSSS_CipherType_HMAC,
#else
/* The applet denies ReadObject on a symmetric key object
* created without a read policy, and pre-7.2 middleware has
* no way to grant one, so keep the Binary derive target
* which ReadObject allows by default */
kSSS_CipherType_Binary,
#endif
keySize,
kKeyObject_Mode_Transient);
}
#if defined(SSS_HAVE_SE05X_VER_GTE_07_02) && SSS_HAVE_SE05X_VER_GTE_07_02
if (status == kStatus_SSS_Success) {
byte keyBuf[CURVE25519_KEYSIZE];
#if defined(SSS_HAVE_SE05X_VER_GTE_07_02) && SSS_HAVE_SE05X_VER_GTE_07_02
sss_policy_u commonPol;
sss_policy_t derivePolicy;
#endif
/* Try to delete existing key first, ignore return since will
* fail if no key exists yet */
@@ -3506,8 +3525,7 @@ int se050_curve25519_shared_secret(curve25519_key* private_key,
* secret exactly, so the object must be created before the
* derive (returns SW 0x6985 otherwise) */
XMEMSET(keyBuf, 0, sizeof(keyBuf));
#if defined(SSS_HAVE_SE05X_VER_GTE_07_02) && SSS_HAVE_SE05X_VER_GTE_07_02
/* Applet 7.2 denies ReadObject on a symmetric key object created
/* The applet denies ReadObject on a symmetric key object created
* with no policy attached (SW 0x6986), so the derived secret
* could not be exported. Attach a policy allowing the host to
* read the secret back, overwrite the object and delete it; an
@@ -3525,28 +3543,34 @@ int se050_curve25519_shared_secret(curve25519_key* private_key,
status = sss_key_store_set_key(&host_keystore, &deriveKey,
keyBuf, keySize, keySize * 8, &derivePolicy,
sizeof(derivePolicy));
#else
status = sss_key_store_set_key(&host_keystore, &deriveKey,
keyBuf, keySize, keySize * 8, NULL, 0);
#endif
if (status == kStatus_SSS_Success) {
deriveKeyCreated = 1;
}
}
#endif
if (status == kStatus_SSS_Success) {
status = sss_derive_key_context_init(&ctx_derive_key, cfg_se050_i2c_pi,
&ref_private_key, kAlgorithm_SSS_ECDH,
kMode_SSS_ComputeSharedSecret);
if (status == kStatus_SSS_Success) {
#if !(defined(SSS_HAVE_SE05X_VER_GTE_07_02) && SSS_HAVE_SE05X_VER_GTE_07_02)
/* Try to delete existing key first, ignore return since will
* fail if no key exists yet */
sss_key_store_erase_key(&host_keystore, &deriveKey);
#endif
status = sss_derive_key_dh(&ctx_derive_key, &ref_public_key,
&deriveKey);
}
if (status == kStatus_SSS_Success) {
size_t outlenSz = sizeof(out->point);
size_t outlenSzBits = outlenSz * 8;
#if defined(SSS_HAVE_SE05X_VER_GTE_07_02) && SSS_HAVE_SE05X_VER_GTE_07_02
/* sss_key_store_get_key has no HMAC read case, so read the
* object back as AES type (both are a plain ReadObject) */
deriveKey.cipherType = kSSS_CipherType_AES;
#else
deriveKeyCreated = 1;
#endif
/* derived key export */
status = sss_key_store_get_key(&host_keystore, &deriveKey,
out->point, &outlenSz, &outlenSzBits);