| 1 | package publicrelease |
| 2 | |
| 3 | import ( |
| 4 | "crypto/ed25519" |
| 5 | "encoding/base64" |
| 6 | "errors" |
| 7 | "regexp" |
| 8 | "strings" |
| 9 | ) |
| 10 | |
| 11 | // ErrSums is every way a checksum list can fail VerifySums. |
| 12 | var ErrSums = errors.New("publicrelease: signed checksum list refused") |
| 13 | |
| 14 | var sumLine = regexp.MustCompile(`^([0-9a-f]{64}) (\S+)$`) |
| 15 | |
| 16 | // VerifySums checks a release's SHA256SUMS.txt against its .sig with pubKey |
| 17 | // (base64 ed25519, over the raw sums bytes, as Feed.Sums checks it) and |
| 18 | // returns asset name to sha256. Unlike Feed.Sums it is strict, because its |
| 19 | // caller signs what it returns into deployment authority: every line must be |
| 20 | // sha256sum's text form, "<64 lowercase hex> <name>", each name once, and a |
| 21 | // list with no lines is refused. It reads nothing from the network. |
| 22 | func VerifySums(pubKey string, sums []byte, sig string) (map[string]string, error) { |
| 23 | pub, err := base64.StdEncoding.DecodeString(pubKey) |
| 24 | if err != nil || len(pub) != ed25519.PublicKeySize { |
| 25 | return nil, ErrSums |
| 26 | } |
| 27 | raw, err := base64.StdEncoding.DecodeString(strings.TrimSpace(sig)) |
| 28 | if err != nil || len(raw) != ed25519.SignatureSize || !ed25519.Verify(ed25519.PublicKey(pub), sums, raw) { |
| 29 | return nil, ErrSums |
| 30 | } |
| 31 | text := string(sums) |
| 32 | if !strings.HasSuffix(text, "\n") { |
| 33 | return nil, ErrSums |
| 34 | } |
| 35 | out := map[string]string{} |
| 36 | for _, line := range strings.Split(strings.TrimSuffix(text, "\n"), "\n") { |
| 37 | m := sumLine.FindStringSubmatch(line) |
| 38 | if m == nil { |
| 39 | return nil, ErrSums |
| 40 | } |
| 41 | if _, dup := out[m[2]]; dup { |
| 42 | return nil, ErrSums |
| 43 | } |
| 44 | out[m[2]] = m[1] |
| 45 | } |
| 46 | return out, nil |
| 47 | } |
| 48 | |
amadan