From 6232291caebc2dc1365cdb422ed16c09c06b3f28 Mon Sep 17 00:00:00 2001
From: Ophestra Umiker <cat@ophivana.moe>
Date: Wed, 9 Oct 2024 20:39:27 +0900
Subject: [PATCH] ldd: implement strict ldd output parser

Fortify needs to internally resolve helper program sandbox config. They are considered trusted and runs under the privileged UID so ldd output is used to determine libraries they need inside the sandbox environment.

Signed-off-by: Ophestra Umiker <cat@ophivana.moe>
---
 ldd/error.go | 11 +++++++
 ldd/ldd.go   | 84 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 95 insertions(+)
 create mode 100644 ldd/error.go
 create mode 100644 ldd/ldd.go

diff --git a/ldd/error.go b/ldd/error.go
new file mode 100644
index 0000000..51aef94
--- /dev/null
+++ b/ldd/error.go
@@ -0,0 +1,11 @@
+package ldd
+
+import "fmt"
+
+type EntryUnexpectedSegmentsError struct {
+	Entry string
+}
+
+func (e *EntryUnexpectedSegmentsError) Error() string {
+	return fmt.Sprintf("unexpected segments in entry %q", e.Entry)
+}
diff --git a/ldd/ldd.go b/ldd/ldd.go
new file mode 100644
index 0000000..989aeca
--- /dev/null
+++ b/ldd/ldd.go
@@ -0,0 +1,84 @@
+package ldd
+
+import (
+	"errors"
+	"fmt"
+	"math"
+	"os"
+	"os/exec"
+	"path"
+	"strconv"
+	"strings"
+)
+
+var (
+	ErrUnexpectedSeparator = errors.New("unexpected separator")
+	ErrPathNotAbsolute     = errors.New("path not absolute")
+	ErrBadLocationFormat   = errors.New("bad location format")
+)
+
+type Entry struct {
+	Name     string `json:"name,omitempty"`
+	Path     string `json:"path,omitempty"`
+	Location uint64 `json:"location"`
+}
+
+func Exec(p string) ([]*Entry, error) {
+	t := exec.Command("ldd", p)
+	t.Stdout = new(strings.Builder)
+	t.Stderr = os.Stderr
+
+	if err := t.Run(); err != nil {
+		return nil, err
+	}
+
+	out := t.Stdout.(fmt.Stringer).String()
+	payload := strings.Split(out, "\n")
+
+	result := make([]*Entry, len(payload))
+
+	for i, ent := range payload {
+		if len(ent) == 0 {
+			continue
+		}
+
+		segment := strings.SplitN(ent, " ", 5)
+
+		var iL int
+
+		switch len(segment) {
+		case 2: // /lib/ld-musl-x86_64.so.1 (0x7f04d14ef000)
+			iL = 1
+			result[i] = &Entry{Name: segment[0]}
+		case 4: // libc.musl-x86_64.so.1 => /lib/ld-musl-x86_64.so.1 (0x7f04d14ef000)
+			iL = 3
+			if segment[1] != "=>" {
+				return nil, ErrUnexpectedSeparator
+			}
+			if !path.IsAbs(segment[2]) {
+				return nil, ErrPathNotAbsolute
+			}
+			result[i] = &Entry{
+				Name: segment[0],
+				Path: segment[2],
+			}
+		default:
+			return nil, &EntryUnexpectedSegmentsError{ent}
+		}
+
+		if loc, err := parseLocation(segment[iL]); err != nil {
+			return nil, err
+		} else {
+			result[i].Location = loc
+		}
+	}
+
+	return result, nil
+}
+
+func parseLocation(s string) (uint64, error) {
+	if len(s) < 4 || s[len(s)-1] != ')' || s[:3] != "(0x" {
+		return math.MaxUint64, ErrBadLocationFormat
+	}
+	return strconv.ParseUint(s[3:len(s)-1], 16, 64)
+}