[Cryptech-Commits] [sw/libhal] 01/01: Track Joachim's keywrap core change to automatically initialize the AIV.

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paul at psgd.org pushed a commit to branch auto_magic
in repository sw/libhal.

commit 92dcc23dd95a6f38a7fa4abc9b7002eff8dcd053
Author: Paul Selkirk <paul at psgd.org>
AuthorDate: Mon Sep 17 17:55:33 2018 -0400

    Track Joachim's keywrap core change to automatically initialize the AIV.
---
 aes_keywrap.c       | 74 ++++++++++++++++++++++++++++-------------------------
 verilog_constants.h |  2 +-
 2 files changed, 40 insertions(+), 36 deletions(-)

diff --git a/aes_keywrap.c b/aes_keywrap.c
index a3e223f..2775b3e 100644
--- a/aes_keywrap.c
+++ b/aes_keywrap.c
@@ -77,12 +77,13 @@ size_t hal_aes_keywrap_ciphertext_length(const size_t plaintext_length)
  * Check the KEK, then load it into the AES core.
  * Note that our AES core only supports 128 and 256 bit keys.
  *
- * This should work without modification for the experimental keywrap core.
+ * This should work without modification for the experimental keywrap core,
+ * because ADDR_KEY0 and ADDR_CONFIG are at the same offsets.
  */
 
-typedef enum { KEK_encrypting, KEK_decrypting } kek_action_t;
+typedef enum { key_encrypting, key_decrypting } key_action_t;
 
-static hal_error_t load_kek(const hal_core_t *core, const uint8_t *K, const size_t K_len, const kek_action_t action)
+static hal_error_t load_kek(const hal_core_t *core, const uint8_t *K, const size_t K_len, const key_action_t action)
 {
   uint8_t config[4];
   hal_error_t err;
@@ -106,10 +107,10 @@ static hal_error_t load_kek(const hal_core_t *core, const uint8_t *K, const size
   }
 
   switch (action) {
-  case KEK_encrypting:
+  case key_encrypting:
     config[3] |=  AES_CONFIG_ENCDEC;
     break;
-  case KEK_decrypting:
+  case key_decrypting:
     config[3] &= ~AES_CONFIG_ENCDEC;
     break;
   default:
@@ -130,11 +131,11 @@ static hal_error_t load_kek(const hal_core_t *core, const uint8_t *K, const size
 
 
 /*
- * Use the experimental keywrap core to wrap/unwrap n 64-bit blocks of plaintext.
+ * Use the experimental keywrap core to wrap/unwrap len bytes of plaintext.
  * The wrapped/unwrapped key is returned in the same buffer.
  */
 
-static hal_error_t do_keywrap_core(const hal_core_t *core, uint8_t * const C, const size_t n)
+static hal_error_t do_keywrap_core(const hal_core_t *core, uint8_t * const C, const size_t len, const key_action_t action)
 {
 #ifndef min
 #define min(a,b) ((a) < (b) ? (a) : (b))
@@ -142,25 +143,26 @@ static hal_error_t do_keywrap_core(const hal_core_t *core, uint8_t * const C, co
 
   hal_error_t err;
 
-  hal_assert(core != NULL && C != NULL && n > 0);
+  hal_assert(core != NULL && C != NULL && len > 0);
 
-  /* n is the number of 64-bit (8-byte) blocks in the input.
-   * KEYWRAP_LEN_R_DATA is the number of 4-byte data registers in the core.
-   */
-  if (n == 0 || n > KEYWRAP_LEN_R_DATA * 2)
+  const size_t calculated_C_len = hal_aes_keywrap_ciphertext_length(len);
+  /* KEYWRAP_LEN_R_DATA is the number of 4-byte data registers in the core. */
+  if (calculated_C_len - 8 > KEYWRAP_LEN_R_DATA * 4)
     return HAL_ERROR_BAD_ARGUMENTS;
 
-  /* write the AIV to A */
-  if ((err = hal_io_write(core, KEYWRAP_ADDR_A0, C, 8)) != HAL_OK)
-    return err;
+  if (action == key_decrypting) {
+    /* write the first 8 bytes to A */
+    if ((err = hal_io_write(core, KEYWRAP_ADDR_A0, C, 8)) != HAL_OK)
+      return err;
+  }
 
-  /* write the length to RLEN */
-  uint32_t nn = htonl(n);
-  if ((err = hal_io_write(core, KEYWRAP_ADDR_RLEN, (const uint8_t *)&nn, 4)) != HAL_OK)
+  /* write the unpadded length to LENGTH */
+  uint32_t nel = htonl(len);
+  if ((err = hal_io_write(core, KEYWRAP_ADDR_LENGTH, (const uint8_t *)&nel, 4)) != HAL_OK)
     return err;
 
   /* write the data to R_DATA */
-  if ((err = hal_io_write(core, KEYWRAP_ADDR_R_DATA, C + 8, 8 * n)) != HAL_OK)
+  if ((err = hal_io_write(core, KEYWRAP_ADDR_R_DATA, C + 8, calculated_C_len - 8)) != HAL_OK)
       return err;
 
   /* start the wrap/unwrap operation, and wait for it to complete */
@@ -172,8 +174,8 @@ static hal_error_t do_keywrap_core(const hal_core_t *core, uint8_t * const C, co
   if ((err = hal_io_read(core, KEYWRAP_ADDR_A0, C, 8)) != HAL_OK)
     return err;
 
-  /* read the data to R_DATA */
-  if ((err = hal_io_read(core, KEYWRAP_ADDR_R_DATA, C + 8, 8 * n)) != HAL_OK)
+  /* read the data from R_DATA */
+  if ((err = hal_io_read(core, KEYWRAP_ADDR_R_DATA, C + 8, calculated_C_len - 8)) != HAL_OK)
       return err;
 
   return HAL_OK;
@@ -256,7 +258,7 @@ hal_error_t hal_aes_keywrap(hal_core_t *core,
       return err;
   }
 
-  if ((err = load_kek(core, K, K_len, KEK_encrypting)) != HAL_OK)
+  if ((err = load_kek(core, K, K_len, key_encrypting)) != HAL_OK)
       goto out;
 
   *C_len = calculated_C_len;
@@ -265,21 +267,22 @@ hal_error_t hal_aes_keywrap(hal_core_t *core,
     memmove(C + 8, Q, m);
   if (m % 8 != 0)
     memset(C + 8 + m, 0, 8 -  (m % 8));
-  C[0] = 0xA6;
-  C[1] = 0x59;
-  C[2] = 0x59;
-  C[3] = 0xA6;
-  C[4] = (m >> 24) & 0xFF;
-  C[5] = (m >> 16) & 0xFF;
-  C[6] = (m >>  8) & 0xFF;
-  C[7] = (m >>  0) & 0xFF;
-
-  n = calculated_C_len/8 - 1;
 
   if (use_keywrap_core) {
-    err = do_keywrap_core(core, C, n);
+    if ((err = do_keywrap_core(core, C, m, key_encrypting)) != HAL_OK)
+      goto out;
   }
   else {
+    C[0] = 0xA6;
+    C[1] = 0x59;
+    C[2] = 0x59;
+    C[3] = 0xA6;
+    C[4] = (m >> 24) & 0xFF;
+    C[5] = (m >> 16) & 0xFF;
+    C[6] = (m >>  8) & 0xFF;
+    C[7] = (m >>  0) & 0xFF;
+
+    n = calculated_C_len/8 - 1;
     if (n == 1) {
       if ((err = do_block(core, C, C + 8)) != HAL_OK)
         goto out;
@@ -345,7 +348,7 @@ hal_error_t hal_aes_keyunwrap(hal_core_t *core,
       return err;
   }
 
-  if ((err = load_kek(core, K, K_len, KEK_decrypting)) != HAL_OK)
+  if ((err = load_kek(core, K, K_len, key_decrypting)) != HAL_OK)
     goto out;
 
   n = (C_len / 8) - 1;
@@ -354,7 +357,8 @@ hal_error_t hal_aes_keyunwrap(hal_core_t *core,
     memmove(Q, C, C_len);
 
   if (use_keywrap_core) {
-    err = do_keywrap_core(core, Q, n);
+    if ((err = do_keywrap_core(core, Q, C_len - 8, key_decrypting)) != HAL_OK)
+      goto out;
   }
   else {
     if (n == 1) {
diff --git a/verilog_constants.h b/verilog_constants.h
index 8735b12..d190589 100644
--- a/verilog_constants.h
+++ b/verilog_constants.h
@@ -307,7 +307,7 @@
 #define KEYWRAP_CONFIG_ENCDEC   (1)
 #define KEYWRAP_CONFIG_KEYLEN   (2)
 
-#define KEYWRAP_ADDR_RLEN       (0x0c)
+#define KEYWRAP_ADDR_LENGTH     (0x0c)
 #define KEYWRAP_ADDR_A0         (0x0e)
 #define KEYWRAP_ADDR_A1         (0x0f)