Merge pull request #314 from gilles-peskine-arm/pkwrite_ECPrivateKey_size-crypto

Fix pk_write with EC key to use a constant size for the private value
diff --git a/docs/getting_started.md b/docs/getting_started.md
index 236c1a2..9938909 100644
--- a/docs/getting_started.md
+++ b/docs/getting_started.md
@@ -72,9 +72,10 @@
 
 This example shows how to import a key:
 ```C
+void import_a_key(const uint8_t *key, size_t key_len)
+{
     psa_status_t status;
     psa_key_attributes_t attributes = PSA_KEY_ATTRIBUTES_INIT;
-    uint8_t data[] = AES_KEY;
     psa_key_handle_t handle;
 
     printf("Import an AES key...\t");
@@ -94,7 +95,7 @@
     psa_set_key_bits(&attributes, 128);
 
     /* Import the key */
-    status = psa_import_key(&attributes, data, sizeof(data), &handle);
+    status = psa_import_key(&attributes, key, key_len, &handle);
     if (status != PSA_SUCCESS) {
         printf("Failed to import key\n");
         return;
@@ -108,6 +109,7 @@
     psa_destroy_key(handle);
 
     mbedtls_psa_crypto_free();
+}
 ```
 
 ### Signing a message using RSA
@@ -123,9 +125,10 @@
 
 This example shows how to sign a hash that has already been calculated:
 ```C
+void sign_a_message_using_rsa(const uint8_t *key, size_t key_len)
+{
     psa_status_t status;
     psa_key_attributes_t attributes = PSA_KEY_ATTRIBUTES_INIT;
-    uint8_t key[] = RSA_KEY;
     uint8_t hash[32] = {0x50, 0xd8, 0x58, 0xe0, 0x98, 0x5e, 0xcc, 0x7f,
                         0x60, 0x41, 0x8a, 0xaf, 0x0c, 0xc5, 0xab, 0x58,
                         0x7f, 0x42, 0xc2, 0x57, 0x0a, 0x88, 0x40, 0x95,
@@ -151,7 +154,7 @@
     psa_set_key_bits(&attributes, 1024);
 
     /* Import the key */
-    status = psa_import_key(&attributes, key, sizeof(key), &handle);
+    status = psa_import_key(&attributes, key, key_len, &handle);
     if (status != PSA_SUCCESS) {
         printf("Failed to import key\n");
         return;
@@ -176,6 +179,7 @@
     psa_destroy_key(handle);
 
     mbedtls_psa_crypto_free();
+}
 ```
 
 ### Using symmetric ciphers
@@ -196,6 +200,8 @@
 
 This example shows how to encrypt data using an AES (Advanced Encryption Standard) key in CBC (Cipher Block Chaining) mode with no padding (assuming all prerequisites have been fulfilled):
 ```c
+void encrypt_with_symmetric_ciphers(const uint8_t *key, size_t key_len)
+{
     enum {
         block_size = PSA_BLOCK_CIPHER_BLOCK_SIZE(PSA_KEY_TYPE_AES),
     };
@@ -205,7 +211,6 @@
     uint8_t plaintext[block_size] = SOME_PLAINTEXT;
     uint8_t iv[block_size];
     size_t iv_len;
-    uint8_t key[] = AES_KEY;
     uint8_t output[block_size];
     size_t output_len;
     psa_key_handle_t handle;
@@ -227,7 +232,7 @@
     psa_set_key_algorithm(&attributes, alg);
     psa_set_key_type(&attributes, PSA_KEY_TYPE_AES);
     psa_set_key_bits(&attributes, 128);
-    status = psa_import_key(&attributes, key, sizeof(key), &handle);
+    status = psa_import_key(&attributes, key, key_len, &handle);
     if (status != PSA_SUCCESS) {
         printf("Failed to import a key\n");
         return;
@@ -266,6 +271,7 @@
     psa_destroy_key(handle);
 
     mbedtls_psa_crypto_free();
+}
 ```
 
 **To decrypt a message with a symmetric cipher:**
@@ -279,6 +285,8 @@
 This example shows how to decrypt encrypted data using an AES key in CBC mode with no padding
 (assuming all prerequisites have been fulfilled):
 ```c
+void decrypt_with_symmetric_ciphers(const uint8_t *key, size_t key_len)
+{
     enum {
         block_size = PSA_BLOCK_CIPHER_BLOCK_SIZE(PSA_KEY_TYPE_AES),
     };
@@ -288,7 +296,6 @@
     psa_cipher_operation_t operation = PSA_CIPHER_OPERATION_INIT;
     uint8_t ciphertext[block_size] = SOME_CIPHERTEXT;
     uint8_t iv[block_size] = ENCRYPTED_WITH_IV;
-    uint8_t key[] = AES_KEY;
     uint8_t output[block_size];
     size_t output_len;
     psa_key_handle_t handle;
@@ -309,7 +316,7 @@
     psa_set_key_algorithm(&attributes, alg);
     psa_set_key_type(&attributes, PSA_KEY_TYPE_AES);
     psa_set_key_bits(&attributes, 128);
-    status = psa_import_key(&attributes, key, sizeof(key), &handle);
+    status = psa_import_key(&attributes, key, key_len, &handle);
     if (status != PSA_SUCCESS) {
         printf("Failed to import a key\n");
         return;
@@ -348,6 +355,7 @@
     psa_destroy_key(handle);
 
     mbedtls_psa_crypto_free();
+}
 ```
 
 #### Handling cipher operation contexts
diff --git a/library/psa_crypto_storage.c b/library/psa_crypto_storage.c
index a27442c..1389fd4 100644
--- a/library/psa_crypto_storage.c
+++ b/library/psa_crypto_storage.c
@@ -419,7 +419,7 @@
 {
     struct psa_storage_info_t p_info;
     psa_status_t status;
-    status = psa_its_get_info( PSA_CRYPTO_ITS_RANDOM_SEED_UID, &p_info );
+    status = psa_its_get_info( PSA_CRYPTO_ITS_TRANSACTION_UID, &p_info );
     if( status == PSA_SUCCESS )
     {
         /* This shouldn't happen: we're trying to start a transaction while