boot: Replace boot_encrypt by boot_enc_encrypt and boot_enc_decrypt

To be able to implement encryption with API that requires different
calls for encryption and encryption, the boot_encrypt
needs to be replaced with encryption/decryption specific functions.

Signed-off-by: Dominik Ermel <dominik.ermel@nordicsemi.no>

boot/boot_serial/src/boot_serial_encryption.c

@@ -171,9 +171,18 @@ decrypt_region_inplace(struct boot_loader_state *state,
  blk_sz = tlv_off - (off + bytes_copied);
  }
  }
- boot_encrypt(BOOT_CURR_ENC(state), slot,
- (off + bytes_copied + idx) - hdr->ih_hdr_size, blk_sz,
- blk_off, &buf[idx]);
+ /* slot determines direction: running on secondary slot (1) means
+ * decryption, running on primary slot (0) means encryption.
+ */
+ if (slot == 0) {
+ boot_enc_encrypt(BOOT_CURR_ENC(state), slot,
+ (off + bytes_copied + idx) - hdr->ih_hdr_size, blk_sz,
+ blk_off, &buf[idx]);
+ } else {
+ boot_enc_decrypt(BOOT_CURR_ENC(state), slot,
+ (off + bytes_copied + idx) - hdr->ih_hdr_size, blk_sz,
+ blk_off, &buf[idx]);
+ }
  }
  rc = flash_area_erase(fap, off + bytes_copied, chunk_sz);
  if (rc != 0) {

boot/bootutil/include/bootutil/enc_key.h

@@ -60,7 +60,9 @@ int boot_enc_load(struct enc_key_data *enc_state, int slot,
  struct boot_status *bs);
 bool boot_enc_valid(struct enc_key_data *enc_state, int image_index,
  const struct flash_area *fap);
-void boot_encrypt(struct enc_key_data *enc_state, int slot,
+void boot_enc_encrypt(struct enc_key_data *enc_state, int slot,
+ uint32_t off, uint32_t sz, uint32_t blk_off, uint8_t *buf);
+void boot_enc_decrypt(struct enc_key_data *enc_state, int slot,
  uint32_t off, uint32_t sz, uint32_t blk_off, uint8_t *buf);
 void boot_enc_zeroize(struct enc_key_data *enc_state);
 

boot/bootutil/src/encrypted.c

@@ -673,10 +673,10 @@ boot_enc_valid(struct enc_key_data *enc_state, int image_index,
 }
 
 void
-boot_encrypt(struct enc_key_data *enc_state, int slot, uint32_t off,
+boot_enc_encrypt(struct enc_key_data *enc_state, int slot, uint32_t off,
  uint32_t sz, uint32_t blk_off, uint8_t *buf)
 {
- struct enc_key_data *enc;
+ struct enc_key_data *enc = &enc_state[slot];
  uint8_t nonce[16];
 
  /* boot_copy_region will call boot_encrypt with sz = 0 when skipping over
@@ -697,6 +697,31 @@ boot_encrypt(struct enc_key_data *enc_state, int slot, uint32_t off,
  bootutil_aes_ctr_encrypt(&enc->aes_ctr, nonce, buf, sz, blk_off, buf);
 }
 
+void
+boot_enc_decrypt(struct enc_key_data *enc_state, int slot, uint32_t off,
+ uint32_t sz, uint32_t blk_off, uint8_t *buf)
+{
+ struct enc_key_data *enc = &enc_state[slot];
+ uint8_t nonce[16];
+
+ /* boot_copy_region will call boot_encrypt with sz = 0 when skipping over
+ the TLVs. */
+ if (sz == 0) {
+ return;
+ }
+
+ memset(nonce, 0, 12);
+ off >>= 4;
+ nonce[12] = (uint8_t)(off >> 24);
+ nonce[13] = (uint8_t)(off >> 16);
+ nonce[14] = (uint8_t)(off >> 8);
+ nonce[15] = (uint8_t)off;
+
+ enc = &enc_state[slot];
+ assert(enc->valid == 1);
+ bootutil_aes_ctr_decrypt(&enc->aes_ctr, nonce, buf, sz, blk_off, buf);
+}
+
 /**
  * Clears encrypted state after use.
  */

boot/bootutil/src/image_validate.c

@@ -150,8 +150,8 @@ bootutil_img_hash(struct enc_key_data *enc_state, int image_index,
  /* Only payload is encrypted (area between header and TLVs) */
  if (off >= hdr_size && off < tlv_off) {
  blk_off = (off - hdr_size) & 0xf;
- boot_encrypt(enc_state, 1, off - hdr_size,
- blk_sz, blk_off, tmp_buf);
+ boot_enc_decrypt(enc_state, 1, off - hdr_size,
+  blk_sz, blk_off, tmp_buf);
  }
  }
 #endif

boot/bootutil/src/loader.c

@@ -1299,6 +1299,15 @@ boot_copy_region(struct boot_loader_state *state,
  (abs_off + idx) - hdr->ih_hdr_size, blk_sz,
  blk_off, &buf[idx]);
  }
+ if (source_slot == 0) {
+ boot_enc_encrypt(BOOT_CURR_ENC(state), source_slot,
+ (abs_off + idx) - hdr->ih_hdr_size, blk_sz,
+ blk_off, &buf[idx]);
+ } else {
+ boot_enc_decrypt(BOOT_CURR_ENC(state), source_slot,
+ (abs_off + idx) - hdr->ih_hdr_size, blk_sz,
+ blk_off, &buf[idx]);
+ }
  }
  }
 #endif
@@ -2772,18 +2781,16 @@ boot_decrypt_and_copy_image_to_sram(struct boot_loader_state *state,
  cur_dst = ram_dst + bytes_copied;
  blk_sz = chunk_sz;
  idx = 0;
+ blk_off = ((bytes_copied) - hdr->ih_hdr_size) & 0xf;
  if (bytes_copied + chunk_sz > tlv_off) {
- /* Going over TLV section
- * Part of the chunk is encrypted payload */
- blk_off = ((bytes_copied) - hdr->ih_hdr_size) & 0xf;
  blk_sz = tlv_off - (bytes_copied);
- boot_encrypt(BOOT_CURR_ENC(state), slot,
- (bytes_copied + idx) - hdr->ih_hdr_size, blk_sz,
- blk_off, cur_dst);
+ }
+ if (slot == 0) {
+ boot_enc_encrypt(BOOT_CURR_ENC(state), slot,
+ (bytes_copied + idx) - hdr->ih_hdr_size, blk_sz,
+ blk_off, cur_dst);
  } else {
- /* Image encrypted payload section */
- blk_off = ((bytes_copied) - hdr->ih_hdr_size) & 0xf;
- boot_encrypt(BOOT_CURR_ENC(state), slot,
+ boot_enc_decrypt(BOOT_CURR_ENC(state), slot,
  (bytes_copied + idx) - hdr->ih_hdr_size, blk_sz,
  blk_off, cur_dst);
  }