rsa: add a structure for the padding

The rsa signature use a padding algorithm. By default, we use the
padding pkcs-1.5. In order to add some new padding algorithm, we
add a padding framework to manage several padding algorithm.
The choice of the padding is done in the file .its.

Signed-off-by: Philippe Reynes <philippe.reynes@softathome.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

include/image.h

@@ -1101,6 +1101,7 @@ struct image_sign_info {
 	int node_offset;		/* Offset of signature node */
 	const char *name;		/* Algorithm name */
 	struct checksum_algo *checksum;	/* Checksum algorithm information */
+	struct padding_algo *padding;	/* Padding algorithm information */
 	struct crypto_algo *crypto;	/* Crypto algorithm information */
 	const void *fdt_blob;		/* FDT containing public keys */
 	int required_keynode;		/* Node offset of key to use: -1=any */
@@ -1186,6 +1187,13 @@ struct crypto_algo {
 		      uint8_t *sig, uint sig_len);
 };
 
+struct padding_algo {
+	const char *name;
+	int (*verify)(struct image_sign_info *info,
+		      uint8_t *pad, int pad_len,
+		      const uint8_t *hash, int hash_len);
+};
+
 /**
  * image_get_checksum_algo() - Look up a checksum algorithm
  *
@@ -1202,6 +1210,14 @@ struct checksum_algo *image_get_checksum_algo(const char *full_name);
  */
 struct crypto_algo *image_get_crypto_algo(const char *full_name);
 
+/**
+ * image_get_padding_algo() - Look up a padding algorithm
+ *
+ * @param name		Name of padding algorithm
+ * @return pointer to algorithm information, or NULL if not found
+ */
+struct padding_algo *image_get_padding_algo(const char *name);
+
 /**
  * fit_image_verify_required_sigs() - Verify signatures marked as 'required'
  *