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Darwin: fix sockaddr_un overflow in makeAddressUnix for long paths #230

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Merged
swhitty merged 1 commit into from
Jul 22, 2026
Merged

Darwin: fix sockaddr_un overflow in makeAddressUnix for long paths #230

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9 changes: 6 additions & 3 deletions FlyingSocks/Sources/Socket+Darwin.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -89,12 +89,15 @@ extension Socket {
static func makeAddressUnix(path: String) -> Darwin.sockaddr_un {
var addr = Darwin.sockaddr_un()
addr.sun_family = sa_family_t(AF_UNIX)
let pathCount = min(path.utf8.count, 104)
// Darwin <sys/un.h> declares `char sun_path[104]`; reserve the last byte
// for the NUL terminator that String(cString:) and unlink() read back.
let pathCount = min(path.utf8.count, 103)
let len = UInt8(MemoryLayout<UInt8>.size + MemoryLayout<sa_family_t>.size + pathCount + 1)
_ = withUnsafeMutablePointer(to: &addr.sun_path.0) { ptr in
withUnsafeMutablePointer(to: &addr.sun_path.0) { ptr in
path.withCString {
strncpy(ptr, $0, Int(len))
_ = strncpy(ptr, $0, pathCount)
}
ptr[pathCount] = 0
}
addr.sun_len = len
return addr
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26 changes: 25 additions & 1 deletion FlyingSocks/Tests/SocketAddressTests.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -148,6 +148,30 @@ struct SocketAddressTests {
)
}

#if canImport(Darwin)
@Test
func unixMaxLengthPath_IsCorrectlyDecodedFromStorage() throws {
let path = "/tmp/" + String(repeating: "x", count: 98)
let addr = sockaddr_un.unix(path: path)

#expect(Int(addr.sun_len) <= MemoryLayout<sockaddr_un>.size)
#expect(
try Socket.makeAddress(from: addr.makeStorage()) == .unix(path)
)
}

@Test
func unixOverlongPath_TruncatesWithoutOverflow() throws {
let path = "/tmp/" + String(repeating: "x", count: 99)
let addr = sockaddr_un.unix(path: path)

#expect(Int(addr.sun_len) <= MemoryLayout<sockaddr_un>.size)
#expect(
try Socket.makeAddress(from: addr.makeStorage()) == .unix(String(path.prefix(103)))
)
}
#endif

#if canImport(Glibc) || canImport(Musl) || canImport(Android)
@Test
func unixAbstractNamespace_IsCorrectlyDecodedFromStorage() throws {
Expand Down Expand Up @@ -268,7 +292,7 @@ struct SocketAddressTests {
func maximumPathLengthForUnixDomainSocket() {
var addrUn = sockaddr_un()
addrUn.sun_family = sa_family_t(AF_UNIX)
let maxPathLength = MemoryLayout<sockaddr_un>.size - MemoryLayout<sa_family_t>.size - 1
let maxPathLength = MemoryLayout.size(ofValue: addrUn.sun_path) - 1
let maxPath = String(repeating: "a", count: maxPathLength)
_ = maxPath.withCString { pathPtr in
memcpy(&addrUn.sun_path, pathPtr, maxPath.count + 1)
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