Revise the remaining steps that needed to report failures

Signed-off-by: Vladimir Diaz <[email protected]>

Author: vladimir-v-diaz

tuf-spec.md

@@ -1077,7 +1077,8 @@ used to download the timestamp metadata file is of the fixed form FILENAME.EXT
   * **2.3**. **Check for a freeze attack.** The latest known time should be
   lower than the expiration timestamp in the new timestamp metadata file.  If
   so, the new timestamp metadata file becomes the trusted timestamp metadata
-  file.
+  file.  If the new timestamp metadata file has expired, discard it and report
+  the potential freeze attack.
 
 **3**. **Download snapshot metadata file**, up to the number of bytes specified
 in the timestamp metadata file.  If consistent snapshots are not used (see
@@ -1090,10 +1091,13 @@ non-volatile storage as FILENAME.EXT.
 
   * **3.1**. **Check against timestamp metadata.** The hashes and version number
   of the new snapshot metadata file MUST match the hashes and version number
-  listed in timestamp metadata.
+  listed in timestamp metadata.  If hashes and version do not match, discard
+  the new snapshot metadata and report the failure.
 
-  * **3.2**. **Check signatures.** The snapshot metadata file MUST have been
-  signed by a threshold of keys specified in the trusted root metadata file.
+  * **3.2**. **Check signatures.** The new snapshot metadata file MUST have
+  been signed by a threshold of keys specified in the trusted root metadata
+  file.  If the new snapshot metadata file is not signed as required, discard
+  it and report the signature failure.
 
   * **3.3**. **Check for a rollback attack.**
 
@@ -1103,19 +1107,22 @@ non-volatile storage as FILENAME.EXT.
 
     * **3.3.2**. The version number of the trusted snapshot metadata file, if
     any, MUST be less than or equal to the version number of the new snapshot
-    metadata file.
+    metadata file.  If the new snapshot metadata file is older than the trusted
+    metadata file, discard it and report the potential rollback attack.
 
     * **3.3.3**. The version number of the targets metadata file, and all
     delegated targets metadata files (if any), in the trusted snapshot metadata
     file, if any, MUST be less than or equal to its version number in the new
     snapshot metadata file. Furthermore, any targets metadata filename that was
     listed in the trusted snapshot metadata file, if any, MUST continue to be
-    listed in the new snapshot metadata file.
+    listed in the new snapshot metadata file.  If any of these conditions are
+    not met, discard the new snaphot metadadata file and report the failure.
 
   * **3.4**. **Check for a freeze attack.** The latest known time should be
   lower than the expiration timestamp in the new snapshot metadata file.  If
   so, the new snapshot metadata file becomes the trusted snapshot metadata
-  file.
+  file. If the new snaphshot metadata file is expired, discard it and report
+  the potential freeze attack.
 
 **4**. **Download the top-level targets metadata file**, up to either the
 number of bytes specified in the snapshot metadata file, or some Z number of
@@ -1131,19 +1138,25 @@ non-volatile storage as FILENAME.EXT.
   * **4.1**. **Check against snapshot metadata.** The hashes (if any), and
   version number of the new targets metadata file MUST match the trusted
   snapshot metadata.  This is done, in part, to prevent a mix-and-match attack
-  by man-in-the-middle attackers.
+  by man-in-the-middle attackers.  If the new targets metadata file does not
+  match, discard it and report the failure.
 
   * **4.2**. **Check for an arbitrary software attack.** The new targets
   metadata file MUST have been signed by a threshold of keys specified in the
-  trusted root metadata file.
+  trusted root metadata file.  If the new targets metadat file is not signed
+  as required, discard it and report the failure.
 
   * **4.3**. **Check for a rollback attack.** The version number of the trusted
   targets metadata file, if any, MUST be less than or equal to the version
-  number of the new targets metadata file.
+  number of the new targets metadata file.  If the new targets metadata file
+  is older than the trusted targets metadata file, discard it and report
+  the potential rollback attack.
 
   * **4.4**. **Check for a freeze attack.** The latest known time should be
   lower than the expiration timestamp in the new targets metadata file.  If so,
-  the new targets metadata file becomes the trusted targets metadata file.
+  the new targets metadata file becomes the trusted targets metadata file.  If
+  the new targets metadata file is expired, discard it and report the potential
+  freeze attack.
 
   * **4.5**. **Perform a preorder depth-first search for metadata about the
   desired target, beginning with the top-level targets role.**  Note: If