117 lines
2.5 KiB
Go
117 lines
2.5 KiB
Go
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package plugingetter
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import (
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"bytes"
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"encoding/hex"
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"fmt"
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"hash"
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"io"
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"os"
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"strings"
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)
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// A ChecksumError is returned when a checksum differs
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type ChecksumError struct {
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Hash hash.Hash
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Actual []byte
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Expected []byte
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File string
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}
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func (cerr *ChecksumError) Error() string {
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if cerr == nil {
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return "<nil>"
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}
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return fmt.Sprintf(
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"Checksums (%T) did not match.\nExpected: %s\nGot : %s\n",
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cerr.Hash, // ex: *sha256.digest
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hex.EncodeToString(cerr.Expected),
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hex.EncodeToString(cerr.Actual),
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)
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}
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type Checksum []byte
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func (c Checksum) String() string { return hex.EncodeToString(c) }
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type FileChecksum struct {
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Filename string
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Expected Checksum
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Checksummer
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}
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type Checksummer struct {
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// Something like md5 or sha256
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Type string
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// Hash function
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hash.Hash
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}
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func (c *Checksummer) FileExt() string {
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return "_" + strings.ToUpper(c.Type) + "SUM"
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}
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// GetCacheChecksumOfFile will extract the checksum from file `filePath + c.FileExt()`.
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// It expects the checksum file to only contains the checksum and nothing else.
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func (c *Checksummer) GetCacheChecksumOfFile(filePath string) ([]byte, error) {
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checksumFile := filePath + c.FileExt()
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f, err := os.Open(checksumFile)
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if err != nil {
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return nil, err
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}
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defer f.Close()
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return c.ParseChecksum(f)
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}
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// ParseChecksum expects the checksum reader to only contain the checksum and
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// nothing else.
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func (c *Checksummer) ParseChecksum(f io.Reader) (Checksum, error) {
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res := make([]byte, c.Hash.Size())
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_, err := hex.NewDecoder(f).Read(res)
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if err == io.EOF {
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err = nil
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}
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return res, err
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}
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// ChecksumFile compares the expected checksum to the checksum of the file in
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// filePath using the hash function.
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func (c *Checksummer) ChecksumFile(expected []byte, filePath string) error {
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f, err := os.Open(filePath)
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if err != nil {
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return fmt.Errorf("Checksum: failed to open file for checksum: %s", err)
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}
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defer f.Close()
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err = c.Checksum(expected, f)
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if cerr, ok := err.(*ChecksumError); ok {
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cerr.File = filePath
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}
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return err
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}
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func (c *Checksummer) Sum(f io.Reader) ([]byte, error) {
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c.Hash.Reset()
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if _, err := io.Copy(c.Hash, f); err != nil {
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return nil, fmt.Errorf("Failed to hash: %s", err)
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}
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return c.Hash.Sum(nil), nil
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}
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func (c *Checksummer) Checksum(expected []byte, f io.Reader) error {
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actual, err := c.Sum(f)
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if err != nil {
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return err
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}
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if !bytes.Equal(actual, expected) {
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return &ChecksumError{
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Hash: c.Hash,
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Actual: actual,
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Expected: expected,
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}
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}
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return nil
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}
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