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Package fetch: add executable detection for Mach-O file headers #21555

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Merged
merged 2 commits into from
Jan 21, 2025
Merged

Package fetch: add executable detection for Mach-O file headers #21555

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35b7d0c
Package fetch: add executable detection for Mach-O file headers
fabioarnold Sep 30, 2024
b410f9d
Update `FileHeader` test
fabioarnold Jan 14, 2025
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41 changes: 31 additions & 10 deletions src/Package/Fetch.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -1789,12 +1789,9 @@ test {
_ = UnpackResult;
}

// Detects executable header: ELF magic header or shebang line.
// Detects executable header: ELF or Macho-O magic header or shebang line.
const FileHeader = struct {
const elf_magic = std.elf.MAGIC;
const shebang = "#!";

header: [@max(elf_magic.len, shebang.len)]u8 = undefined,
header: [4]u8 = undefined,
bytes_read: usize = 0,

pub fn update(self: *FileHeader, buf: []const u8) void {
Expand All @@ -1804,22 +1801,46 @@ const FileHeader = struct {
self.bytes_read += n;
}

fn isScript(self: *FileHeader) bool {
const shebang = "#!";
return std.mem.eql(u8, self.header[0..@min(self.bytes_read, shebang.len)], shebang);
}

fn isElf(self: *FileHeader) bool {
const elf_magic = std.elf.MAGIC;
return std.mem.eql(u8, self.header[0..@min(self.bytes_read, elf_magic.len)], elf_magic);
}

fn isMachO(self: *FileHeader) bool {
if (self.bytes_read < 4) return false;
const magic_number = std.mem.readInt(u32, &self.header, builtin.cpu.arch.endian());
return magic_number == std.macho.MH_MAGIC or
magic_number == std.macho.MH_MAGIC_64 or
magic_number == std.macho.FAT_MAGIC or
magic_number == std.macho.FAT_MAGIC_64;
}

pub fn isExecutable(self: *FileHeader) bool {
return std.mem.eql(u8, self.header[0..@min(self.bytes_read, shebang.len)], shebang) or
std.mem.eql(u8, self.header[0..@min(self.bytes_read, elf_magic.len)], elf_magic);
return self.isScript() or self.isElf() or self.isMachO();
}
};

test FileHeader {
var h: FileHeader = .{};
try std.testing.expect(!h.isExecutable());

h.update(FileHeader.elf_magic[0..2]);
const elf_magic = std.elf.MAGIC;
h.update(elf_magic[0..2]);
try std.testing.expect(!h.isExecutable());
h.update(FileHeader.elf_magic[2..4]);
h.update(elf_magic[2..4]);
try std.testing.expect(h.isExecutable());

h.update(elf_magic[2..4]);
try std.testing.expect(h.isExecutable());

h.update(FileHeader.elf_magic[2..4]);
const macho64_magic_bytes = [_]u8{ 0xCF, 0xFA, 0xED, 0xFE };
h.bytes_read = 0;
h.update(&macho64_magic_bytes);
try std.testing.expect(h.isExecutable());
}

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