libgocryptfs/internal/readpassword/passfile.go

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package readpassword
import (
"bytes"
"os"
"github.com/rfjakob/gocryptfs/internal/exitcodes"
"github.com/rfjakob/gocryptfs/internal/tlog"
)
func readPassFile(passfile string) []byte {
tlog.Info.Printf("passfile: reading from file %q", passfile)
f, err := os.Open(passfile)
if err != nil {
tlog.Fatal.Printf("fatal: passfile: could not open %q: %v", passfile, err)
os.Exit(exitcodes.ReadPassword)
}
defer f.Close()
// +1 for an optional trailing newline,
// +2 so we can detect if maxPasswordLen is exceeded.
buf := make([]byte, maxPasswordLen+2)
n, err := f.Read(buf)
if err != nil {
tlog.Fatal.Printf("fatal: passfile: could not read from %q: %v", passfile, err)
os.Exit(exitcodes.ReadPassword)
}
buf = buf[:n]
// Split into first line and "trailing garbage"
lines := bytes.SplitN(buf, []byte("\n"), 2)
if len(lines[0]) == 0 {
tlog.Fatal.Printf("fatal: passfile: empty first line in %q", passfile)
os.Exit(exitcodes.ReadPassword)
}
if len(lines[0]) > maxPasswordLen {
tlog.Fatal.Printf("fatal: passfile: max password length (%d bytes) exceeded", maxPasswordLen)
os.Exit(exitcodes.ReadPassword)
}
if len(lines) > 1 && len(lines[1]) > 0 {
tlog.Warn.Printf("passfile: ignoring trailing garbage (%d bytes) after first line",
len(lines[1]))
}
return lines[0]
}