validate dst path to temp root.

go.mod

@@ -5,7 +5,7 @@ go 1.22.7
 require (
 	github.com/Defacto2/archive v1.0.3
 	github.com/Defacto2/helper v1.1.3
-	github.com/Defacto2/magicnumber v1.0.2
+	github.com/Defacto2/magicnumber v1.0.3
 	github.com/Defacto2/releaser v1.0.4
 	github.com/caarlos0/env/v11 v11.2.2
 	github.com/carlmjohnson/versioninfo v0.22.5

go.sum

@@ -73,8 +73,8 @@ github.com/Defacto2/archive v1.0.3 h1:7iidbFf3yBJ0e2XWsx/uhB4ciWysE5nMejzRCQSgop
 github.com/Defacto2/archive v1.0.3/go.mod h1:1nM/bBCir4nz1t/HFYnZk9tXc/yaWzJTEu1+CDoGyUE=
 github.com/Defacto2/helper v1.1.3 h1:BS7PqOR31AtXC+BTKM9oL2OE+NLrdLqd8xyBxwAsCps=
 github.com/Defacto2/helper v1.1.3/go.mod h1:IikMmXvNy3uOcLk4/cEi9mb+xcx8AHPsSmVGd8SKpB0=
-github.com/Defacto2/magicnumber v1.0.2 h1:zElw+GCZiS0n4xta6g7WDp9ovx1RZKRYL+q9zj0l4dk=
-github.com/Defacto2/magicnumber v1.0.2/go.mod h1:U64FNRfNyv5tBE6jPU00ortSbrIAVO5V34tZFwaeA3s=
+github.com/Defacto2/magicnumber v1.0.3 h1:XOQA3Zsx7C78bultofaSdeUuw8busZx7YnkHly6PGbU=
+github.com/Defacto2/magicnumber v1.0.3/go.mod h1:U64FNRfNyv5tBE6jPU00ortSbrIAVO5V34tZFwaeA3s=
 github.com/Defacto2/releaser v1.0.4 h1:dM7epo3Rk+l2NAH4/dMHzo9QCIC6VejhptlhPUtfg3U=
 github.com/Defacto2/releaser v1.0.4/go.mod h1:Jt9HqJDl4ol1oKFb2efvO+8d8buFwSYfn/Trh7O3oLw=
 github.com/Masterminds/goutils v1.1.1/go.mod h1:8cTjp+g8YejhMuvIA5y2vz3BpJxksy863GQaJW2MFNU=

internal/command/command.go

@@ -43,6 +43,7 @@ var (
 	ErrIsDir  = errors.New("file is a directory")
 	ErrIsFile = errors.New("directory path points to a file")
 	ErrMatch  = errors.New("no match value is present")
+	ErrPath   = errors.New("path is not permitted")
 	ErrVers   = errors.New("version mismatch")
 	ErrZap    = errors.New("zap logger instance is nil")
 )

internal/command/images.go

@@ -12,6 +12,7 @@ import (
 	"os"
 	"path/filepath"
 	"slices"
+	"strings"
 	"sync"
 
 	"github.com/Defacto2/helper"
@@ -308,18 +309,21 @@ func (dir Dirs) PictureImager(debug *zap.SugaredLogger, src, unid string) error
 // can be used by the ANSILOVE command to create a PNG image. 80 columns and 29 rows are
 // works well with a 400x400 pixel thumbnail.
 func TextCrop(src, dst string) error {
+	if !validDst(dst) {
+		return fmt.Errorf("text crop dst %w", ErrPath)
+	}
 	srcFile, err := os.Open(src)
 	if err != nil {
-		return fmt.Errorf("write 80x29 open %w", err)
+		return fmt.Errorf("text crop open %w", err)
 	}
 	defer srcFile.Close()
 
-	if magicnumber.Ansi(srcFile) {
+	if magicnumber.CSI(srcFile) {
 		return nil
 	}
 	dstFile, err := os.Create(dst)
 	if err != nil {
-		return fmt.Errorf("write 80x29 create %w", err)
+		return fmt.Errorf("text crop create %w", err)
 	}
 	defer dstFile.Close()
 
@@ -348,7 +352,7 @@ func TextCrop(src, dst string) error {
 		}
 		_, err := writer.WriteString(line + "\n")
 		if err != nil {
-			return fmt.Errorf("write 80x29 writer string %w", err)
+			return fmt.Errorf("text crop writer string %w", err)
 		}
 		// intentionally skip the first line in a file
 		// as sometimes these contain non-printable characters and control codes.
@@ -359,11 +363,20 @@ func TextCrop(src, dst string) error {
 		rowCount++
 	}
 	if err := scanner.Err(); err != nil {
-		return fmt.Errorf("write 80x29 scanner %w", err)
+		return fmt.Errorf("text crop scanner %w", err)
 	}
 	return nil
 }
 
+func validDst(name string) bool {
+	tempDir := os.TempDir()
+	if absPath, err := filepath.Abs(filepath.Join(tempDir, name)); err != nil ||
+		!strings.HasPrefix(absPath, tempDir) {
+		return false
+	}
+	return true
+}
+
 func textCropper(src, unid string) (string, error) {
 	path, err := helper.MkContent(src + "-textimager")
 	if err != nil {