forked from TrueCloudLab/distribution
131 lines
3.5 KiB
Go
131 lines
3.5 KiB
Go
package digest
|
|
|
|
import (
|
|
"fmt"
|
|
"hash"
|
|
"io"
|
|
"regexp"
|
|
"strings"
|
|
)
|
|
|
|
const (
|
|
// DigestSha256EmptyTar is the canonical sha256 digest of empty data
|
|
DigestSha256EmptyTar = "sha256:e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
|
|
)
|
|
|
|
// Digest allows simple protection of hex formatted digest strings, prefixed
|
|
// by their algorithm. Strings of type Digest have some guarantee of being in
|
|
// the correct format and it provides quick access to the components of a
|
|
// digest string.
|
|
//
|
|
// The following is an example of the contents of Digest types:
|
|
//
|
|
// sha256:7173b809ca12ec5dee4506cd86be934c4596dd234ee82c0662eac04a8c2c71dc
|
|
//
|
|
// This allows to abstract the digest behind this type and work only in those
|
|
// terms.
|
|
type Digest string
|
|
|
|
// NewDigest returns a Digest from alg and a hash.Hash object.
|
|
func NewDigest(alg Algorithm, h hash.Hash) Digest {
|
|
return Digest(fmt.Sprintf("%s:%x", alg, h.Sum(nil)))
|
|
}
|
|
|
|
// NewDigestFromHex returns a Digest from alg and a the hex encoded digest.
|
|
func NewDigestFromHex(alg, hex string) Digest {
|
|
return Digest(fmt.Sprintf("%s:%s", alg, hex))
|
|
}
|
|
|
|
// DigestRegexp matches valid digest types.
|
|
var DigestRegexp = regexp.MustCompile(`[a-zA-Z0-9-_+.]+:[a-fA-F0-9]+`)
|
|
|
|
// DigestRegexpAnchored matches valid digest types, anchored to the start and end of the match.
|
|
var DigestRegexpAnchored = regexp.MustCompile(`^` + DigestRegexp.String() + `$`)
|
|
|
|
var (
|
|
// ErrDigestInvalidFormat returned when digest format invalid.
|
|
ErrDigestInvalidFormat = fmt.Errorf("invalid checksum digest format")
|
|
|
|
// ErrDigestInvalidLength returned when digest has invalid length.
|
|
ErrDigestInvalidLength = fmt.Errorf("invalid checksum digest length")
|
|
|
|
// ErrDigestUnsupported returned when the digest algorithm is unsupported.
|
|
ErrDigestUnsupported = fmt.Errorf("unsupported digest algorithm")
|
|
)
|
|
|
|
// ParseDigest parses s and returns the validated digest object. An error will
|
|
// be returned if the format is invalid.
|
|
func ParseDigest(s string) (Digest, error) {
|
|
d := Digest(s)
|
|
|
|
return d, d.Validate()
|
|
}
|
|
|
|
// FromReader returns the most valid digest for the underlying content using
|
|
// the canonical digest algorithm.
|
|
func FromReader(rd io.Reader) (Digest, error) {
|
|
return Canonical.FromReader(rd)
|
|
}
|
|
|
|
// FromBytes digests the input and returns a Digest.
|
|
func FromBytes(p []byte) Digest {
|
|
return Canonical.FromBytes(p)
|
|
}
|
|
|
|
// Validate checks that the contents of d is a valid digest, returning an
|
|
// error if not.
|
|
func (d Digest) Validate() error {
|
|
s := string(d)
|
|
|
|
if !DigestRegexpAnchored.MatchString(s) {
|
|
return ErrDigestInvalidFormat
|
|
}
|
|
|
|
i := strings.Index(s, ":")
|
|
if i < 0 {
|
|
return ErrDigestInvalidFormat
|
|
}
|
|
|
|
// case: "sha256:" with no hex.
|
|
if i+1 == len(s) {
|
|
return ErrDigestInvalidFormat
|
|
}
|
|
|
|
switch algorithm := Algorithm(s[:i]); algorithm {
|
|
case SHA256, SHA384, SHA512:
|
|
if algorithm.Size()*2 != len(s[i+1:]) {
|
|
return ErrDigestInvalidLength
|
|
}
|
|
break
|
|
default:
|
|
return ErrDigestUnsupported
|
|
}
|
|
|
|
return nil
|
|
}
|
|
|
|
// Algorithm returns the algorithm portion of the digest. This will panic if
|
|
// the underlying digest is not in a valid format.
|
|
func (d Digest) Algorithm() Algorithm {
|
|
return Algorithm(d[:d.sepIndex()])
|
|
}
|
|
|
|
// Hex returns the hex digest portion of the digest. This will panic if the
|
|
// underlying digest is not in a valid format.
|
|
func (d Digest) Hex() string {
|
|
return string(d[d.sepIndex()+1:])
|
|
}
|
|
|
|
func (d Digest) String() string {
|
|
return string(d)
|
|
}
|
|
|
|
func (d Digest) sepIndex() int {
|
|
i := strings.Index(string(d), ":")
|
|
|
|
if i < 0 {
|
|
panic("could not find ':' in digest: " + d)
|
|
}
|
|
|
|
return i
|
|
}
|