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| 1 | +package digest |
| 2 | + |
| 3 | +import ( |
| 4 | + "fmt" |
| 5 | + "hash" |
| 6 | + "io" |
| 7 | + "regexp" |
| 8 | + "strings" |
| 9 | +) |
| 10 | + |
| 11 | +const ( |
| 12 | + // DigestSha256EmptyTar is the canonical sha256 digest of empty data |
| 13 | + DigestSha256EmptyTar = "sha256:e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855" |
| 14 | +) |
| 15 | + |
| 16 | +// Digest allows simple protection of hex formatted digest strings, prefixed |
| 17 | +// by their algorithm. Strings of type Digest have some guarantee of being in |
| 18 | +// the correct format and it provides quick access to the components of a |
| 19 | +// digest string. |
| 20 | +// |
| 21 | +// The following is an example of the contents of Digest types: |
| 22 | +// |
| 23 | +// sha256:7173b809ca12ec5dee4506cd86be934c4596dd234ee82c0662eac04a8c2c71dc |
| 24 | +// |
| 25 | +// This allows to abstract the digest behind this type and work only in those |
| 26 | +// terms. |
| 27 | +type Digest string |
| 28 | + |
| 29 | +// NewDigest returns a Digest from alg and a hash.Hash object. |
| 30 | +func NewDigest(alg Algorithm, h hash.Hash) Digest { |
| 31 | + return NewDigestFromBytes(alg, h.Sum(nil)) |
| 32 | +} |
| 33 | + |
| 34 | +// NewDigestFromBytes returns a new digest from the byte contents of p. |
| 35 | +// Typically, this can come from hash.Hash.Sum(...) or xxx.SumXXX(...) |
| 36 | +// functions. This is also useful for rebuilding digests from binary |
| 37 | +// serializations. |
| 38 | +func NewDigestFromBytes(alg Algorithm, p []byte) Digest { |
| 39 | + return Digest(fmt.Sprintf("%s:%x", alg, p)) |
| 40 | +} |
| 41 | + |
| 42 | +// NewDigestFromHex returns a Digest from alg and a the hex encoded digest. |
| 43 | +func NewDigestFromHex(alg, hex string) Digest { |
| 44 | + return Digest(fmt.Sprintf("%s:%s", alg, hex)) |
| 45 | +} |
| 46 | + |
| 47 | +// DigestRegexp matches valid digest types. |
| 48 | +var DigestRegexp = regexp.MustCompile(`[a-zA-Z0-9-_+.]+:[a-fA-F0-9]+`) |
| 49 | + |
| 50 | +// DigestRegexpAnchored matches valid digest types, anchored to the start and end of the match. |
| 51 | +var DigestRegexpAnchored = regexp.MustCompile(`^` + DigestRegexp.String() + `$`) |
| 52 | + |
| 53 | +var ( |
| 54 | + // ErrDigestInvalidFormat returned when digest format invalid. |
| 55 | + ErrDigestInvalidFormat = fmt.Errorf("invalid checksum digest format") |
| 56 | + |
| 57 | + // ErrDigestInvalidLength returned when digest has invalid length. |
| 58 | + ErrDigestInvalidLength = fmt.Errorf("invalid checksum digest length") |
| 59 | + |
| 60 | + // ErrDigestUnsupported returned when the digest algorithm is unsupported. |
| 61 | + ErrDigestUnsupported = fmt.Errorf("unsupported digest algorithm") |
| 62 | +) |
| 63 | + |
| 64 | +// ParseDigest parses s and returns the validated digest object. An error will |
| 65 | +// be returned if the format is invalid. |
| 66 | +func ParseDigest(s string) (Digest, error) { |
| 67 | + d := Digest(s) |
| 68 | + |
| 69 | + return d, d.Validate() |
| 70 | +} |
| 71 | + |
| 72 | +// FromReader returns the most valid digest for the underlying content using |
| 73 | +// the canonical digest algorithm. |
| 74 | +func FromReader(rd io.Reader) (Digest, error) { |
| 75 | + return Canonical.FromReader(rd) |
| 76 | +} |
| 77 | + |
| 78 | +// FromBytes digests the input and returns a Digest. |
| 79 | +func FromBytes(p []byte) Digest { |
| 80 | + return Canonical.FromBytes(p) |
| 81 | +} |
| 82 | + |
| 83 | +// Validate checks that the contents of d is a valid digest, returning an |
| 84 | +// error if not. |
| 85 | +func (d Digest) Validate() error { |
| 86 | + s := string(d) |
| 87 | + |
| 88 | + if !DigestRegexpAnchored.MatchString(s) { |
| 89 | + return ErrDigestInvalidFormat |
| 90 | + } |
| 91 | + |
| 92 | + i := strings.Index(s, ":") |
| 93 | + if i < 0 { |
| 94 | + return ErrDigestInvalidFormat |
| 95 | + } |
| 96 | + |
| 97 | + // case: "sha256:" with no hex. |
| 98 | + if i+1 == len(s) { |
| 99 | + return ErrDigestInvalidFormat |
| 100 | + } |
| 101 | + |
| 102 | + switch algorithm := Algorithm(s[:i]); algorithm { |
| 103 | + case SHA256, SHA384, SHA512: |
| 104 | + if algorithm.Size()*2 != len(s[i+1:]) { |
| 105 | + return ErrDigestInvalidLength |
| 106 | + } |
| 107 | + break |
| 108 | + default: |
| 109 | + return ErrDigestUnsupported |
| 110 | + } |
| 111 | + |
| 112 | + return nil |
| 113 | +} |
| 114 | + |
| 115 | +// Algorithm returns the algorithm portion of the digest. This will panic if |
| 116 | +// the underlying digest is not in a valid format. |
| 117 | +func (d Digest) Algorithm() Algorithm { |
| 118 | + return Algorithm(d[:d.sepIndex()]) |
| 119 | +} |
| 120 | + |
| 121 | +// Hex returns the hex digest portion of the digest. This will panic if the |
| 122 | +// underlying digest is not in a valid format. |
| 123 | +func (d Digest) Hex() string { |
| 124 | + return string(d[d.sepIndex()+1:]) |
| 125 | +} |
| 126 | + |
| 127 | +func (d Digest) String() string { |
| 128 | + return string(d) |
| 129 | +} |
| 130 | + |
| 131 | +func (d Digest) sepIndex() int { |
| 132 | + i := strings.Index(string(d), ":") |
| 133 | + |
| 134 | + if i < 0 { |
| 135 | + panic("could not find ':' in digest: " + d) |
| 136 | + } |
| 137 | + |
| 138 | + return i |
| 139 | +} |
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