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package ldd
import (
"bytes"
"context"
"errors"
"io"
"os"
"os/exec"
"time"
"hakurei.app/check"
"hakurei.app/container"
"hakurei.app/container/fhs"
"hakurei.app/container/seccomp"
"hakurei.app/container/std"
"hakurei.app/message"
)
const (
// msgStaticSuffix is the suffix of message printed to stderr by musl on a
// statically linked program.
msgStaticSuffix = ": Not a valid dynamic program"
// msgStaticGlibc is a substring of the message printed to stderr by glibc
// on a statically linked program.
msgStaticGlibc = "not a dynamic executable"
// lddName is the file name of ldd(1) passed to exec.LookPath.
lddName = "ldd"
// lddTimeout is the maximum duration ldd(1) is allowed to ran for before it
// is terminated.
lddTimeout = 4 * time.Second
)
// Resolve runs ldd(1) in a strict sandbox and connects its stdout to a [Decoder].
//
// The returned error has concrete type
// [exec.Error] or [check.AbsoluteError] for fault during lookup of ldd(1),
// [os.SyscallError] for fault creating the stdout pipe,
// [container.StartError] for fault during either stage of container setup.
// Otherwise, it passes through the return values of [Decoder.Decode].
func Resolve(
ctx context.Context,
msg message.Msg,
pathname *check.Absolute,
) ([]*Entry, error) {
if pathname == nil {
if p, err := os.Executable(); err != nil {
return nil, err
} else if pathname, err = check.NewAbs(p); err != nil {
return nil, err
}
}
c, cancel := context.WithTimeout(ctx, lddTimeout)
defer cancel()
var toolPath *check.Absolute
if s, err := exec.LookPath(lddName); err != nil {
return nil, err
} else if toolPath, err = check.NewAbs(s); err != nil {
return nil, err
}
z := container.NewCommand(c, msg, toolPath, lddName, pathname.String())
z.Hostname = "hakurei-" + lddName
z.SeccompFlags |= seccomp.AllowMultiarch
z.SeccompPresets |= std.PresetStrict
stderr := new(bytes.Buffer)
z.Stderr = stderr
z.
Bind(fhs.AbsRoot, fhs.AbsRoot, 0).
Proc(fhs.AbsProc).
Dev(fhs.AbsDev, false)
var d *Decoder
if r, err := z.StdoutPipe(); err != nil {
return nil, err
} else {
d = NewDecoder(r)
}
if err := z.Start(); err != nil {
return nil, err
}
defer func() { _, _ = io.Copy(os.Stderr, stderr) }()
if err := z.Serve(); err != nil {
return nil, err
}
entries, decodeErr := d.Decode()
if decodeErr != nil {
// do not cancel on successful decode to avoid racing with ldd(1) termination
cancel()
}
if err := z.Wait(); err != nil {
m := stderr.Bytes()
if bytes.Contains(m, []byte(msgStaticSuffix)) || bytes.Contains(m, []byte(msgStaticGlibc)) {
return nil, nil
}
if decodeErr != nil {
return nil, errors.Join(decodeErr, err)
}
return nil, err
}
return entries, decodeErr
}
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