Don't fail if the image contains no base sha

+ Added --no-base-sha option to sign
wolfSSL · Nov 22, 2024 · 3a69b0e · 3a69b0e
1 parent adb0204
commit 3a69b0e
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Showing 5 changed files with 65 additions and 30 deletions.
diff --git a/.github/workflows/test-powerfail-simulator.yml b/.github/workflows/test-powerfail-simulator.yml
@@ -235,6 +235,14 @@ jobs:
         run: |
           tools/scripts/sim-update-powerfail-resume.sh
 
+      - name: Rebuild without SHA of base image to test compatibility
+        run: |
+          make clean && make test-sim-internal-flash-with-delta-update-no-base-sha
+
+      - name: Run sunny day update test (DELTA with no-base-sha)
+        run: |
+          tools/scripts/sim-sunnyday-update.sh
+
       - name: Rebuild with wrong delta base version
         run: |
           make clean && make test-sim-internal-flash-with-wrong-delta-update

diff --git a/docs/Signing.md b/docs/Signing.md
@@ -180,6 +180,15 @@ result is stored in a file ending in `_signed_diff.bin`.
 
 The compression scheme used is Bentley–McIlroy.
 
+Options:
+  * `--no-base-sha` : Avoid adding the sha of the base image to the manifest header.
+    By default, the sign tool appends the sha of the base image to the manifest header,
+    so wolfBoot will refuse to start a delta update if the sha does not match the
+    one of the existing image. However, this takes up 32 to 48 bytes extra in the
+    manifest header, so this option is available to provide compatibility on 
+    existing installations without this feature, where the header size does not
+    allow to accommodate the field
+
 
 #### Policy signing (for sealing/unsealing with a TPM)
 

diff --git a/src/update_flash.c b/src/update_flash.c
@@ -340,10 +340,15 @@ static int wolfBoot_delta_update(struct wolfBoot_image *boot,
     delta_base_v = wolfBoot_get_diffbase_version(PART_UPDATE);
 
     if (delta_base_hash_sz != WOLFBOOT_SHA_DIGEST_SIZE) {
-        wolfBoot_printf("Delta update: Base hash size mismatch"
-                " (size: %x expected %x)\n", delta_base_hash_sz,
-                WOLFBOOT_SHA_DIGEST_SIZE);
-        return -1;
+        if (delta_base_hash_sz == 0) {
+            wolfBoot_printf("Warning: delta update: Base hash not found in image\n");
+            delta_base_hash = NULL;
+        } else {
+            wolfBoot_printf("Error: delta update: Base hash size mismatch"
+                    " (size: %x expected %x)\n", delta_base_hash_sz,
+                    WOLFBOOT_SHA_DIGEST_SIZE);
+            return -1;
+        }
     }
 
 #if defined(WOLFBOOT_HASH_SHA256)
@@ -375,8 +380,8 @@ static int wolfBoot_delta_update(struct wolfBoot_image *boot,
             wolfBoot_printf("Delta Base 0x%x != Cur 0x%x\n",
                 cur_v, delta_base_v);
             ret = -1;
-
-        } else if (!resume && memcmp(base_hash, delta_base_hash, base_hash_sz) != 0) {
+        } else if (!resume && delta_base_hash &&
+                memcmp(base_hash, delta_base_hash, base_hash_sz) != 0) {
             /* Wrong base image digest, cannot apply delta patch */
             wolfBoot_printf("Delta Base hash mismatch\n");
             ret = -1;

diff --git a/tools/keytools/sign.c b/tools/keytools/sign.c
@@ -291,6 +291,7 @@ struct cmd_options {
     const char *policy_file;
     const char *encrypt_key_file;
     const char *delta_base_file;
+    int no_base_sha;
     char output_image_file[PATH_MAX];
     char output_diff_file[PATH_MAX];
     char output_encrypted_image_file[PATH_MAX];
@@ -1201,33 +1202,35 @@ static int make_header_ex(int is_diff, uint8_t *pubkey, uint32_t pubkey_sz,
         header_append_tag(header, &header_idx, HDR_IMG_DELTA_INVERSE_SIZE, 4,
                 &patch_inv_len);
 
-        /* Append pad bytes, so base hash is 8-byte aligned */
-        ALIGN_8(header_idx);
-        if (!base_hash) {
-            fprintf(stderr, "Base hash for delta image not found.\n");
-            exit(1);
-        }
-        if (CMD.hash_algo == HASH_SHA256) {
-            if (base_hash_sz != HDR_SHA256_LEN) {
-                fprintf(stderr, "Invalid base hash size for SHA256.\n");
-                exit(1);
-            }
-            header_append_tag(header, &header_idx, HDR_IMG_DELTA_BASE_HASH,
-                    HDR_SHA256_LEN, base_hash);
-        } else if (CMD.hash_algo == HASH_SHA384) {
-            if  (base_hash_sz != HDR_SHA384_LEN) {
-                fprintf(stderr, "Invalid base hash size for SHA384.\n");
+        if (!CMD.no_base_sha) {
+            /* Append pad bytes, so base hash is 8-byte aligned */
+            ALIGN_8(header_idx);
+            if (!base_hash) {
+                fprintf(stderr, "Base hash for delta image not found.\n");
                 exit(1);
             }
-            header_append_tag(header, &header_idx, HDR_IMG_DELTA_BASE_HASH,
-                    HDR_SHA384_LEN, base_hash);
-        } else if (CMD.hash_algo == HASH_SHA3) {
-            if (base_hash_sz != HDR_SHA3_384_LEN) {
-                fprintf(stderr, "Invalid base hash size for SHA3-384.\n");
-                exit(1);
+            if (CMD.hash_algo == HASH_SHA256) {
+                if (base_hash_sz != HDR_SHA256_LEN) {
+                    fprintf(stderr, "Invalid base hash size for SHA256.\n");
+                    exit(1);
+                }
+                header_append_tag(header, &header_idx, HDR_IMG_DELTA_BASE_HASH,
+                        HDR_SHA256_LEN, base_hash);
+            } else if (CMD.hash_algo == HASH_SHA384) {
+                if  (base_hash_sz != HDR_SHA384_LEN) {
+                    fprintf(stderr, "Invalid base hash size for SHA384.\n");
+                    exit(1);
+                }
+                header_append_tag(header, &header_idx, HDR_IMG_DELTA_BASE_HASH,
+                        HDR_SHA384_LEN, base_hash);
+            } else if (CMD.hash_algo == HASH_SHA3) {
+                if (base_hash_sz != HDR_SHA3_384_LEN) {
+                    fprintf(stderr, "Invalid base hash size for SHA3-384.\n");
+                    exit(1);
+                }
+                header_append_tag(header, &header_idx, HDR_IMG_DELTA_BASE_HASH,
+                        HDR_SHA3_384_LEN, base_hash);
             }
-            header_append_tag(header, &header_idx, HDR_IMG_DELTA_BASE_HASH,
-                    HDR_SHA3_384_LEN, base_hash);
         }
     }
 
@@ -2490,6 +2493,8 @@ int main(int argc, char** argv)
         else if (strcmp(argv[i], "--delta") == 0) {
             CMD.delta = 1;
             CMD.delta_base_file = argv[++i];
+        } else if (strcmp(argv[i], "--no-base-sha") == 0) {
+            CMD.no_base_sha = 1;
         }
         else if (strcmp(argv[i], "--no-ts") == 0) {
             CMD.no_ts = 1;

diff --git a/tools/test.mk b/tools/test.mk
@@ -246,6 +246,14 @@ test-sim-internal-flash-with-delta-update:
 		$$(($(WOLFBOOT_PARTITION_UPDATE_ADDRESS)-$(ARCH_FLASH_OFFSET))) test-app/image_v$(TEST_UPDATE_VERSION)_signed_diff.bin \
 		$$(($(WOLFBOOT_PARTITION_SWAP_ADDRESS)-$(ARCH_FLASH_OFFSET))) erased_sec.dd
 
+test-sim-internal-flash-with-delta-update-no-base-sha:
+	make test-sim-internal-flash-with-update DELTA_UPDATE_OPTIONS="--no-base-sha --delta test-app/image_v1_signed.bin"
+	$(Q)$(BINASSEMBLE) internal_flash.dd \
+		0 wolfboot.bin \
+		$$(($(WOLFBOOT_PARTITION_BOOT_ADDRESS) - $(ARCH_FLASH_OFFSET))) test-app/image_v1_signed.bin \
+		$$(($(WOLFBOOT_PARTITION_UPDATE_ADDRESS)-$(ARCH_FLASH_OFFSET))) test-app/image_v$(TEST_UPDATE_VERSION)_signed_diff.bin \
+		$$(($(WOLFBOOT_PARTITION_SWAP_ADDRESS)-$(ARCH_FLASH_OFFSET))) erased_sec.dd
+
 test-sim-internal-flash-with-wrong-delta-update:
 	make test-sim-internal-flash-with-update DELTA_UPDATE_OPTIONS="--delta test-app/image_v1_signed.bin"
 	make test-sim-internal-flash-with-update DELTA_UPDATE_OPTIONS="--delta test-app/image_v2_signed.bin" TEST_UPDATE_VERSION=3