forked from LaconicNetwork/kompose
96 lines
2.6 KiB
Go
96 lines
2.6 KiB
Go
package digest
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import (
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"fmt"
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"hash"
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"regexp"
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"strings"
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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 NewDigestFromBytes(alg, h.Sum(nil))
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}
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// NewDigestFromBytes returns a new digest from the byte contents of p.
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// Typically, this can come from hash.Hash.Sum(...) or xxx.SumXXX(...)
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// functions. This is also useful for rebuilding digests from binary
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// serializations.
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func NewDigestFromBytes(alg Algorithm, p []byte) Digest {
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return Digest(fmt.Sprintf("%s:%x", alg, p))
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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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// 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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func (d Digest) String() string {
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return string(d)
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}
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