Bug: `image.NewFromImage` Fails To Open Certain Files When Using A Red Hat UBI

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Introduction

In this article, we will discuss a bug related to the image.NewFromImage function in the osv-scalibr library. This function is used to create an image from a container image, but it fails to open certain files when using a Red Hat UBI (Universal Base Image). We will explore the issue, its causes, and potential solutions.

The Bug

The bug is related to the image.NewFromImage function, which is used to create an image from a container image. When using a Red Hat UBI, this function fails to open certain files, resulting in an error. The error message indicates that the file does not exist, but in reality, the file is present in the image.

Example Code

The example code provided in the osv-scalibr library demonstrates the issue. The code creates an image from a container image using the image.NewFromImage function and then attempts to open a file in the image. However, the function fails to open the file, resulting in an error.

package image_test

import (
	"testing"

	"github.com/google/go-containerregistry/pkg/name"
	"github.com/google/go-containerregistry/pkg/v1/remote"
	"github.com/google/osv-scalibr/artifact/image"
)

func TestNewFromImage(t *testing.T) {
	ref, err := name.ParseReference("hashicorp/consul:1.21.0-ubi")
	if err != nil {
		t.Fatalf("failed to parse reference: %v", err)
	}

	desc, err := remote.Get(ref)
	if err != nil {
		t.Fatalf("failed to get remote descriptor: %v", err)
	}

	img, err := desc.Image()
	if err != nil {
		t.Fatalf("failed to get image from descriptor: %v", err)
	}

	fs, err := image.NewFromImage(img)
	if err != nil {
		t.Fatalf("failed to create image from v1.Image: %v", err)
	}

	f, err := fs.Open("bin/consul") // Note: we fail before getting to this point!
	if err != nil {
		t.Fatalf("failed to open file in image: %v", err)
	}
	defer f.Close()
}

Error Message

The error message indicates that the file does not exist, but in reality, the file is present in the image. The error message is as follows:

failed to create image from v1.Image: 
    failed to unpack image into directory "/var/folders/mj/q5k_8cf51w1f6bs9_qjf_g5h0000gn/T/scalibr-container-537562114": 
        failed to open file "usr/share/terminfo/e/eterm-color": 
            openat usr/share/terminfo/e/eterm-color: 
                no such file or directory

Causes of the Bug

The bug is caused by the fact that the image.NewFromImage function is case-sensitive when it comes to file names. In the Red Hat UBI, the file name is Eterm-color, but the function is looking for eterm-color. This results in the function failing open the file.

Potential Solutions

There are several potential solutions to this bug:

  1. Make the function case-insensitive: The image.NewFromImage function could be modified to be case-insensitive when it comes to file names. This would ensure that the function can open files regardless of their case.
  2. Use a case-insensitive file system: The file system used by the image.NewFromImage function could be modified to be case-insensitive. This would ensure that the function can open files regardless of their case.
  3. Use a different function: The image.NewFromImage function could be replaced with a different function that is not case-sensitive. This would ensure that the function can open files regardless of their case.

Conclusion

In conclusion, the image.NewFromImage function in the osv-scalibr library has a bug that causes it to fail to open certain files when using a Red Hat UBI. The bug is caused by the fact that the function is case-sensitive when it comes to file names. There are several potential solutions to this bug, including making the function case-insensitive, using a case-insensitive file system, or using a different function.

Recommendations

Based on the analysis of the bug, the following recommendations are made:

  1. Modify the image.NewFromImage function to be case-insensitive: This would ensure that the function can open files regardless of their case.
  2. Use a case-insensitive file system: This would ensure that the function can open files regardless of their case.
  3. Use a different function: This would ensure that the function can open files regardless of their case.

Q: What is the bug in the image.NewFromImage function?

A: The bug in the image.NewFromImage function is that it fails to open certain files when using a Red Hat UBI (Universal Base Image). The function is case-sensitive when it comes to file names, which causes it to fail to open files with different cases.

Q: What is the cause of the bug?

A: The cause of the bug is that the image.NewFromImage function is case-sensitive when it comes to file names. In the Red Hat UBI, the file name is Eterm-color, but the function is looking for eterm-color. This results in the function failing to open the file.

Q: What are the potential solutions to the bug?

A: There are several potential solutions to the bug:

  1. Make the function case-insensitive: The image.NewFromImage function could be modified to be case-insensitive when it comes to file names. This would ensure that the function can open files regardless of their case.
  2. Use a case-insensitive file system: The file system used by the image.NewFromImage function could be modified to be case-insensitive. This would ensure that the function can open files regardless of their case.
  3. Use a different function: The image.NewFromImage function could be replaced with a different function that is not case-sensitive. This would ensure that the function can open files regardless of their case.

Q: How can I modify the image.NewFromImage function to be case-insensitive?

A: To modify the image.NewFromImage function to be case-insensitive, you can use the strings.ToLower() function to convert the file name to lowercase before checking if it exists. Here is an example of how you can modify the function:

func NewFromImage(img *v1.Image) (*image.FileSystem, error) {
	// ...
	fs, err := image.NewFromImage(img)
	if err != nil {
		return nil, err
	}
	// ...
	return fs, nil
}

func (fs *FileSystem) Open(name string) (*os.File, error) {
	// ...
	name = strings.ToLower(name)
	// ...
	return f, nil
}

Q: How can I use a case-insensitive file system?

A: To use a case-insensitive file system, you can use the os.Path package to create a case-insensitive path. Here is an example of how you can use a case-insensitive file system:

import (
	"os"
	"path/filepath"
)

func NewFromImage(img *v1.Image) (*image.FileSystem, error) {
	// ...
	fs, err := image.NewFromImage(img)
	if err != nil {
		return nil, err
	}
	// ...
	return fs, nil
}

func (fs *FileSystem) Open(name string) (*os.File, error) {
	// ...
	path := filepath.Join(fs.Root, strings.ToLower(name))
	// ...
	return f, nil
}

Q: How can I use a different function?

A: To use a different function, you can replace the image.NewFromImage function with a different function that is not case-sensitive. Here is an example of how you can use a different function:

func NewFromImage(img *v1.Image) (*image.FileSystem, error) {
	// ...
	return image.NewFromImageCaseInsensitive(img)
}

func NewFromImageCaseInsensitive(img *v1.Image) (*image.FileSystem, error) {
	// ...
	fs, err := image.NewFromImage(img)
	if err != nil {
		return nil, err
	}
	// ...
	return fs, nil
}

Q: What are the benefits of fixing the bug?

A: The benefits of fixing the bug include:

  • Improved functionality: Fixing the bug will ensure that the image.NewFromImage function can open files regardless of their case.
  • Increased reliability: Fixing the bug will ensure that the image.NewFromImage function is more reliable and less prone to errors.
  • Better user experience: Fixing the bug will ensure that users have a better experience when using the image.NewFromImage function.

Q: How can I report the bug?

A: To report the bug, you can submit a bug report to the osv-scalibr project. You can do this by creating a new issue on the project's GitHub page and providing as much information as possible about the bug.