Add additional sanity checks to RSA verification code.

host/include/signature_digest.h

Index: host/include/signature_digest.h
diff --git a/host/include/signature_digest.h b/host/include/signature_digest.h
index 55662b940b24ecd2ee8fc7d45be1c0c4c99ae28e..40c27036463687f830b9a1aa2a7a235f307cd947 100644
--- a/host/include/signature_digest.h
+++ b/host/include/signature_digest.h
@@ -6,12 +6,12 @@
 #ifndef VBOOT_REFERENCE_SIGNATURE_DIGEST_H_
 #define VBOOT_REFERENCE_SIGNATURE_DIGEST_H_
 
-#include <inttypes.h>
+#include <stdint.h>
 
 /* Returns a buffer with DigestInfo (which depends on [algorithm])
  * prepended to [digest].
  */
-uint8_t* PrependDigestInfo(int algorithm, uint8_t* digest);
+uint8_t* PrependDigestInfo(unsigned int algorithm, uint8_t* digest);
 
 /* Function that outputs the message digest of the contents of a buffer in a
  * format that can be used as input to OpenSSL for an RSA signature.
@@ -22,7 +22,8 @@ uint8_t* PrependDigestInfo(int algorithm, uint8_t* digest);
  * choice of the hash algorithm (see padding.c). Caller owns the returned
  * pointer and must Free() it.
  */
-uint8_t* SignatureDigest(const uint8_t* buf, uint64_t len, int algorithm);
+uint8_t* SignatureDigest(const uint8_t* buf, uint64_t len,
+                         unsigned int algorithm);
 
 /* Calculates the signature on a buffer [buf] of length [len] using
  * the private RSA key file from [key_file] and signature algorithm
@@ -31,5 +32,5 @@ uint8_t* SignatureDigest(const uint8_t* buf, uint64_t len, int algorithm);
  * Returns the signature. Caller owns the buffer and must Free() it.
  */
 uint8_t* SignatureBuf(const uint8_t* buf, uint64_t len, const char* key_file,
-                      int algorithm);
+                      unsigned int algorithm);
 #endif  /* VBOOT_REFERENCE_SIGNATURE_DIGEST_H_ */