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add 25 MB per-file attachment size guard to MessageFormatter

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Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
This commit is contained in:
Felix Förtsch
2026-03-14 13:44:09 +01:00
parent 0ba309c525
commit 961f87359a
2 changed files with 40 additions and 5 deletions
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17
Packages/MagnumOpusCore/Sources/SMTPClient/MessageFormatter.swift
View File

@@ -71,10 +71,21 @@ public enum MessageFormatter: Sendable {
}
/// Format a multipart/mixed message with attachments.
/// Throws `MessageFormatterError.attachmentTooLarge` if any file exceeds 25 MB.
public static func formatMultipart(
_ message: OutgoingMessage,
attachments: [(filename: String, mimeType: String, data: Data)]
) -> String {
) throws -> String {
let maxSize = 25 * 1024 * 1024 // 25 MB
for attachment in attachments {
if attachment.data.count > maxSize {
throw MessageFormatterError.attachmentTooLarge(
filename: attachment.filename,
size: attachment.data.count
)
}
}
let boundary = "=_MagnumOpus_\(UUID().uuidString)"
var headers: [(String, String)] = []
@@ -184,3 +195,7 @@ public enum MessageFormatter: Sendable {
return result
}
}
public enum MessageFormatterError: Error {
case attachmentTooLarge(filename: String, size: Int)
}

28
Packages/MagnumOpusCore/Tests/SMTPClientTests/MessageFormatterTests.swift
View File

@@ -177,7 +177,7 @@ struct MessageFormatterTests {
// MARK: - Multipart Formatting
@Test("format with attachments produces multipart/mixed")
func multipartWithAttachment() {
func multipartWithAttachment() throws {
let message = OutgoingMessage(
from: EmailAddress(address: "alice@example.com"),
to: [EmailAddress(address: "bob@example.com")],
@@ -189,7 +189,7 @@ struct MessageFormatterTests {
(filename: "test.pdf", mimeType: "application/pdf", data: Data("PDF content".utf8)),
]
let formatted = MessageFormatter.formatMultipart(message, attachments: attachments)
let formatted = try MessageFormatter.formatMultipart(message, attachments: attachments)
#expect(formatted.contains("Content-Type: multipart/mixed; boundary="))
#expect(formatted.contains("Content-Type: text/plain; charset=utf-8"))
@@ -225,8 +225,28 @@ struct MessageFormatterTests {
}
}
@Test("formatMultipart throws for file exceeding 25 MB")
func attachmentSizeGuard() {
let message = OutgoingMessage(
from: EmailAddress(address: "alice@example.com"),
to: [EmailAddress(address: "bob@example.com")],
subject: "Big file",
bodyText: "See attached.",
messageId: "test@example.com"
)
// 26 MB attachment
let bigData = Data(repeating: 0xFF, count: 26 * 1024 * 1024)
let attachments: [(filename: String, mimeType: String, data: Data)] = [
(filename: "huge.bin", mimeType: "application/octet-stream", data: bigData),
]
#expect(throws: MessageFormatterError.self) {
try MessageFormatter.formatMultipart(message, attachments: attachments)
}
}
@Test("multiple attachments produce correct number of boundary sections")
func multipleAttachments() {
func multipleAttachments() throws {
let message = OutgoingMessage(
from: EmailAddress(address: "alice@example.com"),
to: [EmailAddress(address: "bob@example.com")],
@@ -239,7 +259,7 @@ struct MessageFormatterTests {
(filename: "b.jpg", mimeType: "image/jpeg", data: Data("B".utf8)),
]
let formatted = MessageFormatter.formatMultipart(message, attachments: attachments)
let formatted = try MessageFormatter.formatMultipart(message, attachments: attachments)
#expect(formatted.contains("a.pdf"))
#expect(formatted.contains("b.jpg"))