Add support for CentOS SUM files

The CentOS Stream SUM files uses format:
  # FILENAME: <size> bytes
  ALGORITHM (FILENAME) = CHECKSUM

Compared to the more common format:
  CHECKSUM  *FILE_A
  CHECKSUM  FILE_B

Use regular expressions to check for filename both
in the middle with parentheses and at the end.
Similarly look for valid checksums at beginning or
end of line. Also look for know checsum patterns in
case file only contain the checksum iteself.

Change-Id: I9e49c1a6c66e51a7b884485f0bcaf7f1802bda33

3 files changed, 180 insertions, 6 deletions

diff --git a/ironic_python_agent/extensions/standby.py b/ironic_python_agent/extensions/standby.py
index 965ce1ef..a79ce9d6 100644
--- a/ironic_python_agent/extensions/standby.py
+++ b/ironic_python_agent/extensions/standby.py
@@ -14,6 +14,7 @@
 
 import hashlib
 import os
+import re
 import tempfile
 import time
 from urllib import parse as urlparse
@@ -107,6 +108,24 @@ def _is_checksum_url(checksum):
         return False
 
 
+MD5_MATCH = r"^([a-fA-F\d]{32})\s"  # MD5 at beginning of line
+MD5_MATCH_END = r"\s([a-fA-F\d]{32})$"  # MD5 at end of line
+MD5_MATCH_ONLY = r"^([a-fA-F\d]{32})$"  # MD5 only
+SHA256_MATCH = r"^([a-fA-F\d]{64})\s"  # SHA256 at beginning of line
+SHA256_MATCH_END = r"\s([a-fA-F\d]{64})$"  # SHA256 at end of line
+SHA256_MATCH_ONLY = r"^([a-fA-F\d]{64})$"  # SHA256 only
+SHA512_MATCH = r"^([a-fA-F\d]{128})\s"  # SHA512 at beginning of line
+SHA512_MATCH_END = r"\s([a-fA-F\d]{128})$"  # SHA512 at end of line
+SHA512_MATCH_ONLY = r"^([a-fA-F\d]{128})$"  # SHA512 only
+FILENAME_MATCH_END = r"\s[*]?{filename}$"  # Filename binary/text end of line
+FILENAME_MATCH_PARENTHESES = r"\s\({filename}\)\s"  # CentOS images
+
+CHECKSUM_MATCHERS = (MD5_MATCH, MD5_MATCH_END, SHA256_MATCH, SHA256_MATCH_END,
+                     SHA512_MATCH, SHA512_MATCH_END)
+CHECKSUM_ONLY_MATCHERS = (MD5_MATCH_ONLY, SHA256_MATCH_ONLY, SHA512_MATCH_ONLY)
+FILENAME_MATCHERS = (FILENAME_MATCH_END, FILENAME_MATCH_PARENTHESES)
+
+
 def _fetch_checksum(checksum, image_info):
     """Fetch checksum from remote location, if needed."""
     if not _is_checksum_url(checksum):
@@ -121,17 +140,33 @@ def _fetch_checksum(checksum, image_info):
     elif len(lines) == 1:
         # Special case - checksums file with only the checksum itself
         if ' ' not in lines[0]:
-            return lines[0]
+            for matcher in CHECKSUM_ONLY_MATCHERS:
+                checksum = re.findall(matcher, lines[0])
+                if checksum:
+                    return checksum[0]
+            raise errors.ImageDownloadError(
+                checksum, ("Invalid checksum file (No valid checksum found) %s"
+                           % lines))
 
     # FIXME(dtantsur): can we assume the same name for all images?
     expected_fname = os.path.basename(urlparse.urlparse(
         image_info['urls'][0]).path)
     for line in lines:
-        checksum, fname = line.strip().split(None, 1)
-        # The star symbol designates binary mode, which is the same as text
-        # mode on GNU systems.
-        if fname.strip().lstrip('*') == expected_fname:
-            return checksum.strip()
+        # Ignore comment lines
+        if line.startswith("#"):
+            continue
+
+        # Ignore checksums for other files
+        for matcher in FILENAME_MATCHERS:
+            if re.findall(matcher.format(filename=expected_fname), line):
+                break
+        else:
+            continue
+
+        for matcher in CHECKSUM_MATCHERS:
+            checksum = re.findall(matcher, line)
+            if checksum:
+                return checksum[0]
 
     raise errors.ImageDownloadError(
         checksum, "Checksum file does not contain name %s" % expected_fname)
diff --git a/ironic_python_agent/tests/unit/extensions/test_standby.py b/ironic_python_agent/tests/unit/extensions/test_standby.py
index fee5ad30..71f3d344 100644
--- a/ironic_python_agent/tests/unit/extensions/test_standby.py
+++ b/ironic_python_agent/tests/unit/extensions/test_standby.py
@@ -1675,6 +1675,113 @@ foobar  irrelevant file.img
         ])
         self.assertEqual(fake_cs, image_download._hash_algo.hexdigest())
 
+    def test_download_image_and_centos_checksum_md5(self, requests_mock,
+                                                    hash_mock):
+        content = ['SpongeBob', 'SquarePants']
+        fake_cs = "019fe036425da1c562f2e9f5299820bf"
+        cs_response = mock.Mock()
+        cs_response.status_code = 200
+        cs_response.text = """
+# centos-image.img: 1005593088 bytes
+MD5 (centos-image.img) = %s
+""" % fake_cs
+        response = mock.Mock()
+        response.status_code = 200
+        response.iter_content.return_value = content
+        requests_mock.side_effect = [cs_response, response]
+
+        image_info = _build_fake_image_info(
+            'http://example.com/path/centos-image.img')
+        image_info['checksum'] = 'http://example.com/checksum'
+        del image_info['os_hash_algo']
+        del image_info['os_hash_value']
+        CONF.set_override('md5_enabled', True)
+        hash_mock.return_value.hexdigest.return_value = fake_cs
+        image_download = standby.ImageDownload(image_info)
+
+        self.assertEqual(content, list(image_download))
+        requests_mock.assert_has_calls([
+            mock.call('http://example.com/checksum', cert=None,
+                      verify=True,
+                      stream=True, proxies={}, timeout=60),
+            mock.call(image_info['urls'][0], cert=None, verify=True,
+                      stream=True, proxies={}, timeout=60),
+        ])
+        self.assertEqual(fake_cs, image_download._hash_algo.hexdigest())
+
+    def test_download_image_and_centos_checksum_sha256(self, requests_mock,
+                                                       hash_mock):
+        content = ['SpongeBob', 'SquarePants']
+        fake_cs = ('3b678e4fb651d450f4970e1647abc9b0a38bff3febd3d558753'
+                   '623c66369a633')
+        cs_response = mock.Mock()
+        cs_response.status_code = 200
+        cs_response.text = """
+# centos-image.img: 1005593088 bytes
+SHA256 (centos-image.img) = %s
+""" % fake_cs
+        response = mock.Mock()
+        response.status_code = 200
+        response.iter_content.return_value = iter(content)
+        requests_mock.side_effect = [cs_response, response]
+
+        image_info = _build_fake_image_info(
+            'http://example.com/path/centos-image.img')
+        image_info['checksum'] = 'http://example.com/checksum'
+        del image_info['os_hash_algo']
+        del image_info['os_hash_value']
+        hash_mock.return_value.hexdigest.return_value = fake_cs
+        image_download = standby.ImageDownload(image_info)
+
+        self.assertEqual(content, list(image_download))
+        requests_mock.assert_has_calls([
+            mock.call('http://example.com/checksum', cert=None,
+                      verify=True,
+                      stream=True, proxies={}, timeout=60),
+            mock.call(image_info['urls'][0], cert=None, verify=True,
+                      stream=True, proxies={}, timeout=60),
+        ])
+        self.assertEqual(fake_cs, image_download._hash_algo.hexdigest())
+        hash_mock.assert_has_calls([
+            mock.call('sha256')])
+
+    def test_download_image_and_centos_checksum_sha512(self, requests_mock,
+                                                       hash_mock):
+        content = ['SpongeBob', 'SquarePants']
+        fake_cs = ('3b678e4fb651d450f4970e1647abc9b0a38bff3febd3d558753'
+                   '623c66369a6333b678e4fb651d450f4970e1647abc9b0a38b'
+                   'ff3febd3d558753623c66369a633')
+        cs_response = mock.Mock()
+        cs_response.status_code = 200
+        cs_response.text = """
+# centos-image.img: 1005593088 bytes
+SHA512 (centos-image.img) = %s
+""" % fake_cs
+        response = mock.Mock()
+        response.status_code = 200
+        response.iter_content.return_value = iter(content)
+        requests_mock.side_effect = [cs_response, response]
+
+        image_info = _build_fake_image_info(
+            'http://example.com/path/centos-image.img')
+        image_info['checksum'] = 'http://example.com/checksum'
+        del image_info['os_hash_algo']
+        del image_info['os_hash_value']
+        hash_mock.return_value.hexdigest.return_value = fake_cs
+        image_download = standby.ImageDownload(image_info)
+
+        self.assertEqual(content, list(image_download))
+        requests_mock.assert_has_calls([
+            mock.call('http://example.com/checksum', cert=None,
+                      verify=True,
+                      stream=True, proxies={}, timeout=60),
+            mock.call(image_info['urls'][0], cert=None, verify=True,
+                      stream=True, proxies={}, timeout=60),
+        ])
+        self.assertEqual(fake_cs, image_download._hash_algo.hexdigest())
+        hash_mock.assert_has_calls([
+            mock.call('sha512')])
+
     def test_download_image_and_checksum_multiple_sha256(self, requests_mock,
                                                          hash_mock):
         content = ['SpongeBob', 'SquarePants']
@@ -1885,3 +1992,24 @@ foobar  irrelevant file.img
                                'Received status code 400 from '
                                'http://example.com/checksum',
                                standby.ImageDownload, image_info)
+
+    def test_download_image_and_invalid_checksum(self, requests_mock,
+                                                 hash_mock):
+        content = ['SpongeBob', 'SquarePants']
+        fake_cs = "invalid"
+        cs_response = mock.Mock()
+        cs_response.status_code = 200
+        cs_response.text = fake_cs + '\n'
+        response = mock.Mock()
+        response.status_code = 200
+        response.iter_content.return_value = content
+        requests_mock.side_effect = [cs_response, response]
+
+        image_info = _build_fake_image_info(
+            'http://example.com/path/image.img')
+        image_info['os_hash_algo'] = 'sha512'
+        image_info['os_hash_value'] = 'http://example.com/checksum'
+        self.assertRaisesRegex(
+            errors.ImageDownloadError,
+            r"Invalid checksum file \(No valid checksum found\) \['invalid'\]",
+            standby.ImageDownload, image_info)
diff --git a/releasenotes/notes/fetc-checksum-support-additional-format-4b29c5cdaa6b8d16.yaml b/releasenotes/notes/fetc-checksum-support-additional-format-4b29c5cdaa6b8d16.yaml
new file mode 100644
index 00000000..0b533b7f
--- /dev/null
+++ b/releasenotes/notes/fetc-checksum-support-additional-format-4b29c5cdaa6b8d16.yaml
@@ -0,0 +1,11 @@
+---
+features:
+  - |
+    Improved parsing of checksum files.
+
+    * Added support for the ``ALGORITHM (FILENAME) = CHECKSUM`` format used by
+      CentOS Stream.
+    * Lines starting with ``#`` are ignored as comments.
+    * If checksum file contain only the checksum itself, the content is
+      validated to ensure it is one of the known checksum types.
+