fix(utils): reject CR/LF in CACAO SIWE single-line fields

EIP-4361 / CAIP-122 single-line fields (domain, statement, aud, version,
nonce, iat, exp, nbf, requestId) must not embed carriage returns or
newlines, or a caller can forge later message lines. Fail closed before
formatting. Parity with walletconnect-monorepo#7311 / utils#280.

Author: SashaMIT

Sources/WalletConnectUtils/SIWE/SIWEFromCacaoPayloadFormatter.swift

@@ -21,6 +21,10 @@ public typealias SignWithXFormatter = SIWEFromCacaoPayloadFormatter
 /// Previously SIWEFromCacaoPayloadFormatter - now supports Sign with X (CAIP-122)
 public struct SIWEFromCacaoPayloadFormatter: SignWithXFormatting {
 
+    public enum Errors: Error, Equatable {
+        case invalidSingleLineField(String)
+    }
+
     public init() {}
 
     public func formatMessage(from payload: CacaoPayload, includeRecapInTheStatement: Bool) throws -> String {
@@ -30,6 +34,27 @@ public struct SIWEFromCacaoPayloadFormatter: SignWithXFormatting {
         let chainId = account.reference
         let namespace = account.namespace
 
+        // EIP-4361 / CAIP-122 single-line fields must not embed CR/LF, or a
+        // caller can forge later lines (URI, Nonce, …). Parity with
+        // walletconnect-monorepo #7311 / walletconnect-utils #280.
+        try assertSingleLine(payload.domain, field: "domain")
+        try assertSingleLine(payload.aud, field: "aud")
+        try assertSingleLine(payload.version, field: "version")
+        try assertSingleLine(payload.nonce, field: "nonce")
+        try assertSingleLine(payload.iat, field: "iat")
+        if let statement = payload.statement {
+            try assertSingleLine(statement, field: "statement")
+        }
+        if let exp = payload.exp {
+            try assertSingleLine(exp, field: "exp")
+        }
+        if let nbf = payload.nbf {
+            try assertSingleLine(nbf, field: "nbf")
+        }
+        if let requestId = payload.requestId {
+            try assertSingleLine(requestId, field: "requestId")
+        }
+
         // Determine chain-specific account type for CAIP-122
         let accountType = getAccountType(for: namespace)
 
@@ -51,6 +76,12 @@ public struct SIWEFromCacaoPayloadFormatter: SignWithXFormatting {
         return formattedMessage
     }
 
+    private func assertSingleLine(_ value: String, field: String) throws {
+        if value.contains("\r") || value.contains("\n") {
+            throw Errors.invalidSingleLineField(field)
+        }
+    }
+
     // CAIP-122: Map chain namespace to account type
     private func getAccountType(for namespace: String) -> String {
         switch namespace {

Tests/WalletConnectSignTests/SIWEFromCacaoPayloadFormatterTests.swift

@@ -289,4 +289,57 @@ class SIWEFromCacaoPayloadFormatterTests: XCTestCase {
         let message = try sut.formatMessage(from: cacaoPayload)
         XCTAssertEqual(message, expectedMessage)
     }
+
+    // MARK: - EIP-4361 single-line field integrity
+
+    func testRejectsDomainWithEmbeddedNewline() throws {
+        let payload = try smugglingPayload(domain: "service.invalid\nURI: https://evil.invalid")
+        XCTAssertThrowsError(try sut.formatMessage(from: payload)) { error in
+            XCTAssertEqual(
+                error as? SIWEFromCacaoPayloadFormatter.Errors,
+                .invalidSingleLineField("domain")
+            )
+        }
+    }
+
+    func testRejectsStatementWithEmbeddedCarriageReturn() throws {
+        let payload = try smugglingPayload(statement: "I accept\rURI: https://evil.invalid")
+        XCTAssertThrowsError(try sut.formatMessage(from: payload)) { error in
+            XCTAssertEqual(
+                error as? SIWEFromCacaoPayloadFormatter.Errors,
+                .invalidSingleLineField("statement")
+            )
+        }
+    }
+
+    func testRejectsAudWithEmbeddedNewline() throws {
+        let payload = try smugglingPayload(aud: "https://service.invalid/login\nNonce: forged")
+        XCTAssertThrowsError(try sut.formatMessage(from: payload)) { error in
+            XCTAssertEqual(
+                error as? SIWEFromCacaoPayloadFormatter.Errors,
+                .invalidSingleLineField("aud")
+            )
+        }
+    }
+
+    private func smugglingPayload(
+        domain: String = "service.invalid",
+        aud: String = "https://service.invalid/login",
+        statement: String? = "I accept the ServiceOrg Terms of Service: https://service.invalid/tos"
+    ) throws -> CacaoPayload {
+        let account = Account.stub()
+        return CacaoPayload(
+            iss: account.did,
+            domain: domain,
+            aud: aud,
+            version: "1",
+            nonce: "32891756",
+            iat: "2021-09-30T16:25:24Z",
+            nbf: nil,
+            exp: nil,
+            statement: statement,
+            requestId: nil,
+            resources: nil
+        )
+    }
 }