Duc-Tam Nguyen
d81b90b38c
Packing with --base pointed at a kage built for another OS used to guess the target from the file name: a base ending in .exe meant Windows, anything else meant the host. That misfired in both directions. A Windows base without the .exe suffix produced a viewer with no extension that will not run on Windows, and an --out name that dropped .exe made the run hint print a macOS quarantine note for a Windows file. Sniff the base's executable header (ELF, PE, Mach-O) instead, so the target OS comes from the bytes rather than the name. A Windows viewer now always gets a .exe suffix, and the run hint names the real target and only mentions Gatekeeper for actual macOS viewers.
58 lines
1.8 KiB
Go
58 lines
1.8 KiB
Go
package pack
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import "os"
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// Executable-format magic numbers, enough to tell the three desktop targets
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// apart by their first bytes. We only need the family (windows, darwin, linux),
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// not the architecture, so the smallest distinguishing prefix is plenty.
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var (
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magicELF = []byte{0x7f, 'E', 'L', 'F'} // Linux, FreeBSD, and other ELF systems
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magicPE = []byte{'M', 'Z'} // Windows PE/COFF (DOS stub header)
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machOLE64 = []byte{0xcf, 0xfa, 0xed, 0xfe} // Mach-O 64-bit, little-endian (amd64, arm64)
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machOLE32 = []byte{0xce, 0xfa, 0xed, 0xfe} // Mach-O 32-bit, little-endian
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machOBE64 = []byte{0xfe, 0xed, 0xfa, 0xcf} // Mach-O 64-bit, big-endian
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machOBE32 = []byte{0xfe, 0xed, 0xfa, 0xce} // Mach-O 32-bit, big-endian
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machOFat = []byte{0xca, 0xfe, 0xba, 0xbe} // Mach-O universal (fat) binary
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)
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// SniffOS reads the first bytes of an executable and returns the GOOS family it
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// was built for: "windows", "darwin", "linux", or "" when the bytes match none
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// of them. It is how pack decides whether a cross-built viewer needs a .exe
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// suffix and which run hint to print, without trusting the base's file name.
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func SniffOS(path string) string {
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f, err := os.Open(path)
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if err != nil {
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return ""
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}
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defer func() { _ = f.Close() }()
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head := make([]byte, 4)
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if _, err := f.ReadAt(head, 0); err != nil {
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return ""
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}
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switch {
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case hasPrefix(head, magicPE):
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return "windows"
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case hasPrefix(head, magicELF):
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return "linux"
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case hasPrefix(head, machOLE64), hasPrefix(head, machOLE32),
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hasPrefix(head, machOBE64), hasPrefix(head, machOBE32),
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hasPrefix(head, machOFat):
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return "darwin"
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default:
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return ""
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}
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}
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func hasPrefix(b, prefix []byte) bool {
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if len(b) < len(prefix) {
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return false
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}
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for i := range prefix {
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if b[i] != prefix[i] {
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return false
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}
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}
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return true
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}
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