Add support for yaml OSCAL files validation (#1091)

* Add support for yaml OSCAL files validation
* Replace pyyaml library with ruamel.yaml This was done to address the concern raised in the PR - #1091 (comment)
* Pin specific versions of PyPI packages.

Co-authored-by: Alexander Stein <[email protected]>

src/utils/util/oscal-content-validator.py

@@ -6,13 +6,16 @@
 import argparse
 from jsonschema import validate
 import xmlschema
+from ruamel.yaml import YAML
 
 
 def _get_oscal_file_type(filename):
     if filename.endswith("json"):
         return "json"
     elif filename.endswith("xml") or filename.endswith("xsd"):
         return "xml"
+    elif filename.endswith("yaml") or filename.endswith("yml"):
+        return "yaml"
     else:
         raise("Not a valid OSCAL file.")
 
@@ -21,6 +24,9 @@ def read_file(filename, ftype):
     with io.open(filename, 'r', encoding="utf-8") as f:
         if ftype == "json":
             filedata = json.load(f)
+        if ftype == "yaml":
+            yaml = YAML()
+            filedata = yaml.load(f)
         else:
             filedata = f.read()
     return filedata, ftype
@@ -41,7 +47,8 @@ def oscal_validator(oscal_schema, oscal_data):
     schema, stype = read_file(oscal_schema, _get_oscal_file_type(oscal_schema))
     data, ftype = read_file(oscal_data, _get_oscal_file_type(oscal_data))
 
-    if ftype == 'json':
+    if ftype == 'json' or ftype == 'yaml':
+        # Yaml files are validated using the json schema
         validate(data, schema)
     if ftype == 'xml':
         xmlschema.validate(data, schema)

src/utils/util/requirements.txt

@@ -1,2 +1,3 @@
-jsonschema
-xmlschema
+jsonschema==4.4.0
+ruamel.yaml==0.17.10
+xmlschema==1.9.2