Fix semicolon parsing in ContentDisposition

Sources/OpenAPIRuntime/Base/ContentDisposition.swift

@@ -102,21 +102,57 @@ struct ContentDisposition: Hashable {
 
 extension ContentDisposition: RawRepresentable {
 
+    /// Splits a value into top-level components on `;`, without splitting inside a quoted value.
+    private static func splitIntoTopLevelComponents(_ rawValue: String) -> [String] {
+        var components: [String] = []
+        var current = ""
+        var isInsideQuotedString = false
+        var iterator = rawValue.makeIterator()
+        while let character = iterator.next() {
+            switch character {
+            case "\\" where isInsideQuotedString:
+                current.append(character)
+                if let escaped = iterator.next() { current.append(escaped) }
+            case "\"":
+                isInsideQuotedString.toggle()
+                current.append(character)
+            case ";" where !isInsideQuotedString:
+                if !current.isEmpty { components.append(current) }
+                current = ""
+            default: current.append(character)
+            }
+        }
+        if !current.isEmpty { components.append(current) }
+        return components.map { $0.trimmingLeadingAndTrailingSpaces }
+    }
+
+    /// Removes surrounding quotes and resolves backslash-escaped characters in a parameter value.
+    private static func unquote(_ value: String) -> String {
+        guard value.count >= 2, value.first == "\"", value.last == "\"" else { return value }
+        return value.dropFirst().dropLast().replacingOccurrences(of: "\\\"", with: "\"")
+            .replacingOccurrences(of: "\\\\", with: "\\")
+    }
+
+    /// Wraps a parameter value in quotes, escaping backslashes and double quotes.
+    private static func quote(_ value: String) -> String {
+        "\"" + value.replacingOccurrences(of: "\\", with: "\\\\").replacingOccurrences(of: "\"", with: "\\\"") + "\""
+    }
+
     /// Creates a new instance with the specified raw value.
     ///
     /// https://datatracker.ietf.org/doc/html/rfc6266#section-4.1
     /// - Parameter rawValue: The raw value to use for the new instance.
     init?(rawValue: String) {
-        var components = rawValue.split(separator: ";").map { $0.trimmingLeadingAndTrailingSpaces }
+        var components = Self.splitIntoTopLevelComponents(rawValue)
         guard !components.isEmpty else { return nil }
         self.dispositionType = DispositionType(rawValue: components.removeFirst())
         let parameterTuples: [(ParameterName, String)] = components.compactMap {
             (component: String) -> (ParameterName, String)? in
             let parameterComponents = component.split(separator: "=", maxSplits: 1)
                 .map { $0.trimmingLeadingAndTrailingSpaces }
             guard parameterComponents.count == 2 else { return nil }
-            let valueWithoutQuotes = parameterComponents[1].trimming(while: { $0 == "\"" })
-            return (.init(rawValue: parameterComponents[0]), valueWithoutQuotes)
+            let value = Self.unquote(parameterComponents[1])
+            return (.init(rawValue: parameterComponents[0]), value)
         }
         self.parameters = Dictionary(parameterTuples, uniquingKeysWith: { a, b in a })
     }
@@ -127,7 +163,7 @@ extension ContentDisposition: RawRepresentable {
         string.append(dispositionType.rawValue)
         if !parameters.isEmpty {
             for (key, value) in parameters.sorted(by: { $0.key.rawValue < $1.key.rawValue }) {
-                string.append("; \(key.rawValue)=\"\(value)\"")
+                string.append("; \(key.rawValue)=\(Self.quote(value))")
             }
         }
         return string

Tests/OpenAPIRuntimeTests/Base/Test_ContentDisposition.swift

@@ -68,6 +68,24 @@ final class Test_ContentDisposition: Test_Runtime {
 
         // Empty
         _test(input: "", parsed: nil, output: nil)
+
+        // A filename value that contains a quote and a semicolon must be a part
+        // of the quoted-string value, not be parsed as the start of another parameter.
+        _test(
+            input: #"form-data; filename="He said \"hi\"; then left.txt"; name="report""#,
+            parsed: ContentDisposition(
+                dispositionType: .formData,
+                parameters: [.name: "report", .filename: #"He said "hi"; then left.txt"#]
+            ),
+            output: #"form-data; filename="He said \"hi\"; then left.txt"; name="report""#
+        )
+
+        // A semicolon embedded in a quoted parameter value must stay as part of the value.
+        _test(
+            input: #"form-data; name="foo; bar""#,
+            parsed: ContentDisposition(dispositionType: .formData, parameters: [.name: "foo; bar"]),
+            output: #"form-data; name="foo; bar""#
+        )
     }
     func testAccessors() {
         var value = ContentDisposition(dispositionType: .formData, parameters: [.name: "Foo"])

Tests/OpenAPIRuntimeTests/Multipart/Test_MultipartValidationSequence.swift

@@ -271,6 +271,30 @@ final class Test_MultipartValidationSequenceStateMachine: Test_Runtime {
         XCTAssertEqual(stateMachine.next(parts[0]), .emitError(.receivedMultipleValuesForSingleValuePart("name")))
     }
 
+    func testFilenameContainingQuoteAndSemicolon() throws {
+        // A filename value that contains a quote and a semicolon must be a part
+        // of the quoted-string value, not be parsed as the start of another parameter.
+        let parts: [MultipartRawPart] = [
+            .init(
+                headerFields: [
+                    .contentDisposition: #"form-data; filename="He said \"hi\"; then left.txt"; name="report""#
+                ],
+                body: "file bytes"
+            )
+        ]
+        XCTAssertEqual(parts[0].filename, #"He said "hi"; then left.txt"#)
+        XCTAssertEqual(parts[0].name, "report")
+        var stateMachine = newStateMachine(
+            allowsUnknownParts: false,
+            requiredExactlyOncePartNames: ["report"],
+            requiredAtLeastOncePartNames: [],
+            atMostOncePartNames: [],
+            zeroOrMoreTimesPartNames: []
+        )
+        XCTAssertEqual(stateMachine.next(parts[0]), .emitPart(parts[0]))
+        XCTAssertEqual(stateMachine.state.remainingExactlyOncePartNames, [])
+    }
+
     func testMissingRequiredAtMostOnce() throws {
         let parts: [MultipartRawPart] = [
             .init(headerFields: [.contentDisposition: #"form-data; name="name""#], body: "24")