bootutil: Add SIG_PURE TLV

The commit adds SIG_PURE TLV that should be used as TLV indicating
that the signature attached to image has been calculated over
entire image, rather than digest of image.

This is generic flag as the "pure" usage may be applied to, potentially,
any signature algorithm.

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

boot/bootutil/include/bootutil/image.h

@@ -101,6 +101,7 @@ struct flash_area;
 #define IMAGE_TLV_ECDSA_SIG         0x22   /* ECDSA of hash output */
 #define IMAGE_TLV_RSA3072_PSS       0x23   /* RSA3072 of hash output */
 #define IMAGE_TLV_ED25519           0x24   /* ed25519 of hash output */
+#define IMAGE_TLV_SIG_PURE          0x25   /* PureEdDSA ed25519 over image */
 #define IMAGE_TLV_ENC_RSA2048       0x30   /* Key encrypted with RSA-OAEP-2048 */
 #define IMAGE_TLV_ENC_KW            0x31   /* Key encrypted with AES-KW 128 or 256*/
 #define IMAGE_TLV_ENC_EC256         0x32   /* Key encrypted with ECIES-EC256 */

scripts/imgtool/image.py

@@ -69,6 +69,7 @@
         'ECDSASIG': 0x22,
         'RSA3072': 0x23,
         'ED25519': 0x24,
+        'SIG_PURE': 0x25,
         'ENCRSA2048': 0x30,
         'ENCKW': 0x31,
         'ENCEC256': 0x32,