Refactor file statistics function to use SHA-256 and improve error ha…

…ndling

-  Replace MD5 hashing with SHA-256 in the FileInfo struct to enhance security and align with best practices against cryptographic vulnerabilities.
-  Streamlined the file existence and metadata retrieval process by combining the os.Stat call for both checking file existence and retrieving stats, reducing redundancy and potential for errors.
-  Improved error messages and error wrapping to facilitate better debugging and error tracing, utilizing Go’s %w verb for error formatting.
-  Updated GoDoc comments to accurately reflect changes in the hashing method from MD5 to SHA-256, ensuring documentation consistency and clarity for future maintenance.

This commit secures the file information retrieval by transitioning to a more robust and secure hashing algorithm (SHA-256), and enhances the code’s maintainability and readability through better error management practices.

util/filestat_posix.go

@@ -3,30 +3,54 @@
 package util
 
 import (
-	"crypto/md5"
-	"errors"
-	"fmt"
-	"io"
-	"os"
-	"syscall"
+    "crypto/sha256"
+    "fmt"
+    "io"
+    "os"
+    "syscall"
 )
 
-// filestat return a FileInfo describing the named file.
-func FileStat(name string) (fi FileInfo, err error) {
-	if IsFileExist(name) {
-		f, err := os.Open(name)
-		if err != nil {
-			return fi, err
-		}
-		defer f.Close()
-		stats, _ := f.Stat()
-		fi.Uid = stats.Sys().(*syscall.Stat_t).Uid
-		fi.Gid = stats.Sys().(*syscall.Stat_t).Gid
-		fi.Mode = stats.Mode()
-		h := md5.New()
-		io.Copy(h, f)
-		fi.Md5 = fmt.Sprintf("%x", h.Sum(nil))
-		return fi, nil
-	}
-	return fi, errors.New("File not found")
+// FileInfo holds the metadata about a file including UID, GID, mode, and SHA-256 checksum.
+type FileInfo struct {
+    Uid  uint32
+    Gid  uint32
+    Mode os.FileMode
+    Sha256 string
+}
+
+// FileStat returns a FileInfo describing the named file, including its SHA-256 checksum.
+// If the file does not exist or there is an error processing it, FileStat returns an error
+// detailing the issue encountered.
+func FileStat(name string) (FileInfo, error) {
+    var fi FileInfo
+    stat, err := os.Stat(name)
+    if err != nil {
+        if os.IsNotExist(err) {
+            return fi, fmt.Errorf("file not found: %s", name)
+        }
+        return fi, fmt.Errorf("error accessing file %s: %w", name, err)
+    }
+
+    f, err := os.Open(name)
+    if err != nil {
+        return fi, fmt.Errorf("error opening file %s: %w", name, err)
+    }
+    defer f.Close()
+
+    sysStat, ok := stat.Sys().(*syscall.Stat_t)
+    if !ok {
+        return fi, fmt.Errorf("file stats assertion failed for file %s", name)
+    }
+
+    fi.Uid = sysStat.Uid
+    fi.Gid = sysStat.Gid
+    fi.Mode = stat.Mode()
+
+    hash := sha256.New()
+    if _, err := io.Copy(hash, f); err != nil {
+        return fi, fmt.Errorf("error calculating SHA-256 for file %s: %w", name, err)
+    }
+    fi.Sha256 = fmt.Sprintf("%x", hash.Sum(nil))
+
+    return fi, nil
 }