Correcting documentation issues:

- Changelog entry is Feature instead of API Change
- Correcting whitespaces around braces
- Also adding defensive mechanism to x509_get_subject_key_id
  to avoid malfunction in case of trailing garbage

Signed-off-by: toth92g <toth92g@gmail.com>

ChangeLog.d/X509Parse_SignatureKeyId_AuthorityKeyId.txt

@@ -1,2 +1,3 @@
-API changes
-   * x509 certificate parse functionality is extended with the possibility of extracting SignatureKeyId and AuthorityKeyId fields
+Features
+   * When parsing X.509 certificates, support the extensions
+     SignatureKeyIdentifier and AuthorityKeyIdentifier.

library/x509_crt.c

@@ -608,6 +608,11 @@ static int x509_get_subject_key_id(unsigned char **p,
         *p += len;
     }
 
+    if (*p != end) {
+        return MBEDTLS_ERR_X509_INVALID_EXTENSIONS +
+               MBEDTLS_ERR_ASN1_LENGTH_MISMATCH;
+    }
+
     return 0;
 }