4c850e7165
tarsum is not actually used by the registry. Remove support for it. Convert numerous uses in unit tests to SHA256. Update docs to remove mentions of tarsums (which were often inaccurate). Remove tarsum dependency. Signed-off-by: Aaron Lehmann <aaron.lehmann@docker.com>
143 lines
3.9 KiB
Go
143 lines
3.9 KiB
Go
package digest
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import (
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"fmt"
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"hash"
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"io"
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"regexp"
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"strings"
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)
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const (
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// DigestSha256EmptyTar is the canonical sha256 digest of empty data
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DigestSha256EmptyTar = "sha256:e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
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)
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// Digest allows simple protection of hex formatted digest strings, prefixed
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// by their algorithm. Strings of type Digest have some guarantee of being in
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// the correct format and it provides quick access to the components of a
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// digest string.
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//
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// The following is an example of the contents of Digest types:
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//
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// sha256:7173b809ca12ec5dee4506cd86be934c4596dd234ee82c0662eac04a8c2c71dc
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//
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// This allows to abstract the digest behind this type and work only in those
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// terms.
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type Digest string
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// NewDigest returns a Digest from alg and a hash.Hash object.
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func NewDigest(alg Algorithm, h hash.Hash) Digest {
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return Digest(fmt.Sprintf("%s:%x", alg, h.Sum(nil)))
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}
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// NewDigestFromHex returns a Digest from alg and a the hex encoded digest.
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func NewDigestFromHex(alg, hex string) Digest {
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return Digest(fmt.Sprintf("%s:%s", alg, hex))
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}
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// DigestRegexp matches valid digest types.
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var DigestRegexp = regexp.MustCompile(`[a-zA-Z0-9-_+.]+:[a-fA-F0-9]+`)
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// DigestRegexpAnchored matches valid digest types, anchored to the start and end of the match.
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var DigestRegexpAnchored = regexp.MustCompile(`^` + DigestRegexp.String() + `$`)
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var (
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// ErrDigestInvalidFormat returned when digest format invalid.
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ErrDigestInvalidFormat = fmt.Errorf("invalid checksum digest format")
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// ErrDigestInvalidLength returned when digest has invalid length.
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ErrDigestInvalidLength = fmt.Errorf("invalid checksum digest length")
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// ErrDigestUnsupported returned when the digest algorithm is unsupported.
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ErrDigestUnsupported = fmt.Errorf("unsupported digest algorithm")
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)
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// ParseDigest parses s and returns the validated digest object. An error will
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// be returned if the format is invalid.
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func ParseDigest(s string) (Digest, error) {
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d := Digest(s)
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return d, d.Validate()
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}
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// FromReader returns the most valid digest for the underlying content using
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// the canonical digest algorithm.
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func FromReader(rd io.Reader) (Digest, error) {
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return Canonical.FromReader(rd)
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}
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// FromBytes digests the input and returns a Digest.
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func FromBytes(p []byte) Digest {
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digester := Canonical.New()
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if _, err := digester.Hash().Write(p); err != nil {
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// Writes to a Hash should never fail. None of the existing
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// hash implementations in the stdlib or hashes vendored
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// here can return errors from Write. Having a panic in this
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// condition instead of having FromBytes return an error value
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// avoids unnecessary error handling paths in all callers.
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panic("write to hash function returned error: " + err.Error())
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}
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return digester.Digest()
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}
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// Validate checks that the contents of d is a valid digest, returning an
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// error if not.
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func (d Digest) Validate() error {
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s := string(d)
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if !DigestRegexpAnchored.MatchString(s) {
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return ErrDigestInvalidFormat
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}
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i := strings.Index(s, ":")
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if i < 0 {
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return ErrDigestInvalidFormat
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}
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// case: "sha256:" with no hex.
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if i+1 == len(s) {
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return ErrDigestInvalidFormat
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}
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switch algorithm := Algorithm(s[:i]); algorithm {
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case SHA256, SHA384, SHA512:
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if algorithm.Size()*2 != len(s[i+1:]) {
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return ErrDigestInvalidLength
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}
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break
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default:
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return ErrDigestUnsupported
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}
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return nil
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}
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// Algorithm returns the algorithm portion of the digest. This will panic if
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// the underlying digest is not in a valid format.
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func (d Digest) Algorithm() Algorithm {
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return Algorithm(d[:d.sepIndex()])
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}
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// Hex returns the hex digest portion of the digest. This will panic if the
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// underlying digest is not in a valid format.
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func (d Digest) Hex() string {
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return string(d[d.sepIndex()+1:])
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}
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func (d Digest) String() string {
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return string(d)
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}
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func (d Digest) sepIndex() int {
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i := strings.Index(string(d), ":")
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if i < 0 {
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panic("could not find ':' in digest: " + d)
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}
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return i
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}
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