Skip to content

Fix crash: bounds-check Localization binary decode against out-of-bounds reads #2218

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
ankuper wants to merge 1 commit into
base: master
Choose a base branch
from
Open

Fix crash: bounds-check Localization binary decode against out-of-bounds reads #2218

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
114 changes: 52 additions & 62 deletions submodules/TelegramCore/Sources/SyncCore/SyncCore_Localization.swift
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -61,91 +61,81 @@ public final class Localization: Codable, Equatable {

let count = (try? container.decode(Int32.self, forKey: "c")) ?? 0
var entries: [LocalizationEntry] = []
if let rawData = try? container.decodeIfPresent(Data.self, forKey: "d") {
if count >= 0, let rawData = try? container.decodeIfPresent(Data.self, forKey: "d") {
let data = ReadBuffer(data: rawData)

for _ in 0 ..< count {
// This buffer is persisted (and can arrive via a server-pushed
// localization update), so a truncated or corrupt record must
// not be trusted blindly: ReadBuffer.read() does a raw memcpy
// with no bounds check, and `0 ..< count` traps on a negative
// count. A bad record previously crashed on decode and then
// crash-looped on every relaunch since the record persists.
// Bail out of the whole parse (keeping entries decoded so far)
// as soon as a length-prefixed read would go out of bounds;
// invalid UTF-8 in an otherwise in-bounds string is unrelated
// to buffer safety and only drops that one entry, as before.
func readLengthPrefixedData() -> Data? {
guard data.offset + 4 <= data.length else { return nil }
var length: Int32 = 0
data.read(&length, offset: 0, length: 4)
guard length >= 0, data.offset + Int(length) <= data.length else { return nil }
let valueData = Data(bytes: data.memory.advanced(by: data.offset), count: Int(length))
data.skip(Int(length))
return valueData
}

outer: for _ in 0 ..< count {
guard data.offset + 1 <= data.length else { break }
var flagsValue: Int8 = 0
data.read(&flagsValue, offset: 0, length: 1)
let flags = LocalizationEntryFlags(rawValue: flagsValue)

var length: Int32 = 0
data.read(&length, offset: 0, length: 4)

let keyData = Data(bytes: data.memory.advanced(by: data.offset), count: Int(length))

guard let keyData = readLengthPrefixedData() else { break }
let key = String(data: keyData, encoding: .utf8)
data.skip(Int(length))


if flags.contains(.pluralized) {
var zero: String?
var one: String?
var two: String?
var few: String?
var many: String?
var other: String?

if flags.contains(.hasZero) {
length = 0
data.read(&length, offset: 0, length: 4)
let valueData = Data(bytes: data.memory.advanced(by: data.offset), count: Int(length))
let value = String(data: valueData, encoding: .utf8)
data.skip(Int(length))
zero = value
}

guard let valueData = readLengthPrefixedData() else { break outer }
zero = String(data: valueData, encoding: .utf8)
}

if flags.contains(.hasOne) {
length = 0
data.read(&length, offset: 0, length: 4)
let valueData = Data(bytes: data.memory.advanced(by: data.offset), count: Int(length))
let value = String(data: valueData, encoding: .utf8)
data.skip(Int(length))
one = value
}

guard let valueData = readLengthPrefixedData() else { break outer }
one = String(data: valueData, encoding: .utf8)
}

if flags.contains(.hasTwo) {
length = 0
data.read(&length, offset: 0, length: 4)
let valueData = Data(bytes: data.memory.advanced(by: data.offset), count: Int(length))
let value = String(data: valueData, encoding: .utf8)
data.skip(Int(length))
two = value
}

guard let valueData = readLengthPrefixedData() else { break outer }
two = String(data: valueData, encoding: .utf8)
}

if flags.contains(.hasFew) {
length = 0
data.read(&length, offset: 0, length: 4)
let valueData = Data(bytes: data.memory.advanced(by: data.offset), count: Int(length))
let value = String(data: valueData, encoding: .utf8)
data.skip(Int(length))
few = value
}

guard let valueData = readLengthPrefixedData() else { break outer }
few = String(data: valueData, encoding: .utf8)
}

if flags.contains(.hasMany) {
length = 0
data.read(&length, offset: 0, length: 4)
let valueData = Data(bytes: data.memory.advanced(by: data.offset), count: Int(length))
let value = String(data: valueData, encoding: .utf8)
data.skip(Int(length))
many = value
}

length = 0
data.read(&length, offset: 0, length: 4)
let valueData = Data(bytes: data.memory.advanced(by: data.offset), count: Int(length))
let value = String(data: valueData, encoding: .utf8)
data.skip(Int(length))
other = value

guard let valueData = readLengthPrefixedData() else { break outer }
many = String(data: valueData, encoding: .utf8)
}

guard let otherData = readLengthPrefixedData() else { break outer }
other = String(data: otherData, encoding: .utf8)

if let key = key, let other = other {
entries.append(.pluralizedString(key: key, zero: zero, one: one, two: two, few: few, many: many, other: other))
}
} else {
length = 0
data.read(&length, offset: 0, length: 4)
let valueData = Data(bytes: data.memory.advanced(by: data.offset), count: Int(length))
guard let valueData = readLengthPrefixedData() else { break }
let value = String(data: valueData, encoding: .utf8)
data.skip(Int(length))


if let key = key, let value = value {
entries.append(.string(key: key, value: value))
}
Expand Down