Fix: repeatedly dereference pom variables (#2781)

* Fix: repeatedly dereference pom variables

Previously, if there was more than one layer of variable indirection in
the pom property (propert A says it has the same value as property B,
property B says it has the same value as property C), then Syft would
only dereference one layer. Add a loop to dereference variables until
either dereferencing fails, or until the variable is completely
dereferenced back to a literal.

Signed-off-by: Will Murphy <will.murphy@anchore.com>

* switch to recursive implementation

Signed-off-by: Will Murphy <will.murphy@anchore.com>

* add test cases for degenerate poms

Signed-off-by: Will Murphy <will.murphy@anchore.com>

* switch to recursive implementation

Signed-off-by: Will Murphy <will.murphy@anchore.com>

* remove redundant pieces of test cases

Signed-off-by: Will Murphy <will.murphy@anchore.com>

---------

Signed-off-by: Will Murphy <will.murphy@anchore.com>

syft/pkg/cataloger/java/parse_pom_xml.go

@@ -230,16 +230,26 @@ func cleanDescription(original *string) (cleaned string) {
 // resolveProperty emulates some maven property resolution logic by looking in the project's variables
 // as well as supporting the project expressions like ${project.parent.groupId}.
 // If no match is found, the entire expression including ${} is returned
-//
-//nolint:gocognit
 func resolveProperty(pom gopom.Project, property *string, propertyName string) string {
 	propertyCase := safeString(property)
 	log.WithFields("existingPropertyValue", propertyCase, "propertyName", propertyName).Trace("resolving property")
+	seenBeforePropertyNames := map[string]struct{}{
+		propertyName: {},
+	}
+	return recursiveResolveProperty(pom, propertyCase, seenBeforePropertyNames)
+}
+
+//nolint:gocognit
+func recursiveResolveProperty(pom gopom.Project, propertyCase string, seenPropertyNames map[string]struct{}) string {
 	return propertyMatcher.ReplaceAllStringFunc(propertyCase, func(match string) string {
 		propertyName := strings.TrimSpace(match[2 : len(match)-1]) // remove leading ${ and trailing }
+		if _, seen := seenPropertyNames[propertyName]; seen {
+			return propertyCase
+		}
 		entries := pomProperties(pom)
 		if value, ok := entries[propertyName]; ok {
-			return value
+			seenPropertyNames[propertyName] = struct{}{}
+			return recursiveResolveProperty(pom, value, seenPropertyNames) // recursively resolve in case a variable points to a variable.
 		}
 
 		// if we don't find anything directly in the pom properties,

syft/pkg/cataloger/java/parse_pom_xml_test.go

@@ -514,6 +514,86 @@ func Test_resolveProperty(t *testing.T) {
 			},
 			expected: "${project.parent.groupId}",
 		},
+		{
+			name:     "double dereference",
+			property: "${springboot.version}",
+			pom: gopom.Project{
+				Parent: &gopom.Parent{
+					Version: stringPointer("1.2.3"),
+				},
+				Properties: &gopom.Properties{
+					Entries: map[string]string{
+						"springboot.version": "${project.parent.version}",
+					},
+				},
+			},
+			expected: "1.2.3",
+		},
+		{
+			name:     "map missing stops double dereference",
+			property: "${springboot.version}",
+			pom: gopom.Project{
+				Parent: &gopom.Parent{
+					Version: stringPointer("1.2.3"),
+				},
+			},
+			expected: "${springboot.version}",
+		},
+		{
+			name:     "resolution halts even if it resolves to a variable",
+			property: "${springboot.version}",
+			pom: gopom.Project{
+				Parent: &gopom.Parent{
+					Version: stringPointer("${undefined.version}"),
+				},
+				Properties: &gopom.Properties{
+					Entries: map[string]string{
+						"springboot.version": "${project.parent.version}",
+					},
+				},
+			},
+			expected: "${undefined.version}",
+		},
+		{
+			name:     "resolution halts even if cyclic",
+			property: "${springboot.version}",
+			pom: gopom.Project{
+				Properties: &gopom.Properties{
+					Entries: map[string]string{
+						"springboot.version": "${springboot.version}",
+					},
+				},
+			},
+			expected: "${springboot.version}",
+		},
+		{
+			name:     "resolution halts even if cyclic more steps",
+			property: "${cyclic.version}",
+			pom: gopom.Project{
+				Properties: &gopom.Properties{
+					Entries: map[string]string{
+						"other.version":      "${cyclic.version}",
+						"springboot.version": "${other.version}",
+						"cyclic.version":     "${springboot.version}",
+					},
+				},
+			},
+			expected: "${cyclic.version}",
+		},
+		{
+			name:     "resolution  halts even if cyclic involving parent",
+			property: "${cyclic.version}",
+			pom: gopom.Project{
+				Properties: &gopom.Properties{
+					Entries: map[string]string{
+						"other.version":      "${cyclic.version}",
+						"springboot.version": "${other.version}",
+						"cyclic.version":     "${springboot.version}",
+					},
+				},
+			},
+			expected: "${cyclic.version}",
+		},
 	}
 
 	for _, test := range tests {