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77 lines
2.5 KiB
Go
77 lines
2.5 KiB
Go
// +build !windows
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package chrootarchive
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import (
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"bytes"
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"io"
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"io/ioutil"
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"os"
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"path/filepath"
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"testing"
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"github.com/docker/docker/pkg/archive"
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"golang.org/x/sys/unix"
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"gotest.tools/assert"
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)
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// Test for CVE-2018-15664
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// Assures that in the case where an "attacker" controlled path is a symlink to
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// some path outside of a container's rootfs that we do not copy data to a
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// container path that will actually overwrite data on the host
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func TestUntarWithMaliciousSymlinks(t *testing.T) {
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dir, err := ioutil.TempDir("", t.Name())
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assert.NilError(t, err)
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defer os.RemoveAll(dir)
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root := filepath.Join(dir, "root")
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err = os.MkdirAll(root, 0755)
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assert.NilError(t, err)
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// Add a file into a directory above root
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// Ensure that we can't access this file while tarring.
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err = ioutil.WriteFile(filepath.Join(dir, "host-file"), []byte("I am a host file"), 0644)
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assert.NilError(t, err)
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// Create some data which which will be copied into the "container" root into
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// the symlinked path.
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// Before this change, the copy would overwrite the "host" content.
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// With this change it should not.
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data := filepath.Join(dir, "data")
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err = os.MkdirAll(data, 0755)
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assert.NilError(t, err)
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err = ioutil.WriteFile(filepath.Join(data, "local-file"), []byte("pwn3d"), 0644)
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assert.NilError(t, err)
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safe := filepath.Join(root, "safe")
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err = unix.Symlink(dir, safe)
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assert.NilError(t, err)
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rdr, err := archive.TarWithOptions(data, &archive.TarOptions{IncludeFiles: []string{"local-file"}, RebaseNames: map[string]string{"local-file": "host-file"}})
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assert.NilError(t, err)
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// Use tee to test both the good case and the bad case w/o recreating the archive
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bufRdr := bytes.NewBuffer(nil)
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tee := io.TeeReader(rdr, bufRdr)
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err = UntarWithRoot(tee, safe, nil, root)
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assert.Assert(t, err != nil)
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assert.ErrorContains(t, err, "open /safe/host-file: no such file or directory")
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// Make sure the "host" file is still in tact
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// Before the fix the host file would be overwritten
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hostData, err := ioutil.ReadFile(filepath.Join(dir, "host-file"))
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assert.NilError(t, err)
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assert.Equal(t, string(hostData), "I am a host file")
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// Now test by chrooting to an attacker controlled path
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// This should succeed as is and overwrite a "host" file
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// Note that this would be a mis-use of this function.
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err = UntarWithRoot(bufRdr, safe, nil, safe)
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assert.NilError(t, err)
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hostData, err = ioutil.ReadFile(filepath.Join(dir, "host-file"))
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assert.NilError(t, err)
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assert.Equal(t, string(hostData), "pwn3d")
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}
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