| 1 | package dbreads |
| 2 | |
| 3 | import ( |
| 4 | "crypto/aes" |
| 5 | "crypto/cipher" |
| 6 | "crypto/ecdh" |
| 7 | "crypto/rand" |
| 8 | "crypto/sha256" |
| 9 | "encoding/base64" |
| 10 | "encoding/binary" |
| 11 | "encoding/json" |
| 12 | "errors" |
| 13 | "io" |
| 14 | "strconv" |
| 15 | |
| 16 | "golang.org/x/crypto/hkdf" |
| 17 | ) |
| 18 | |
| 19 | // Sealing is the appconfig v2 construction (spec §5.6): ECDH P-256 with a |
| 20 | // fresh sender key per seal, HKDF-SHA256 with this package's own info string, |
| 21 | // AES-256-GCM with bound associated data. The wire is raw bytes, never |
| 22 | // base64, in the bucket: "DBR1" || sender key (65) || nonce (12) || ciphertext. |
| 23 | const ( |
| 24 | sealPrefix = "DBR1" |
| 25 | sealEphLen = 65 |
| 26 | sealNonceLen = 12 |
| 27 | // SealOverhead is what sealing adds: under 100 bytes (spec §5.7). |
| 28 | SealOverhead = len(sealPrefix) + sealEphLen + sealNonceLen + 16 |
| 29 | ) |
| 30 | |
| 31 | // The streams a chunk can carry, bound into its associated data. |
| 32 | const ( |
| 33 | StreamRows = "rows" // a query's output |
| 34 | StreamLTX = "ltx" // a pull's planned files (plan 3) |
| 35 | ) |
| 36 | |
| 37 | // ErrSeal is any sealed object that does not open: wrong key, moved, |
| 38 | // reordered, relabelled, truncated or corrupt. |
| 39 | var ErrSeal = errors.New("dbreads: the sealed bytes do not open") |
| 40 | |
| 41 | var errBadReplyKey = errors.New("dbreads: reply_key is not an uncompressed P-256 point") |
| 42 | |
| 43 | // randReader is a var so a test can make sealing deterministic. |
| 44 | var randReader io.Reader = rand.Reader |
| 45 | |
| 46 | // NewReplyKey is the CLI's ephemeral key pair for one read. The private half |
| 47 | // never leaves the CLI's memory. |
| 48 | func NewReplyKey() (*ecdh.PrivateKey, error) { return ecdh.P256().GenerateKey(randReader) } |
| 49 | |
| 50 | func EncodeReplyKey(pub *ecdh.PublicKey) string { |
| 51 | return base64.StdEncoding.EncodeToString(pub.Bytes()) |
| 52 | } |
| 53 | |
| 54 | func ParseReplyKey(s string) (*ecdh.PublicKey, error) { |
| 55 | raw, err := base64.StdEncoding.Strict().DecodeString(s) |
| 56 | if err != nil || len(raw) != sealEphLen { |
| 57 | return nil, errBadReplyKey |
| 58 | } |
| 59 | pub, err := ecdh.P256().NewPublicKey(raw) |
| 60 | if err != nil { |
| 61 | return nil, errBadReplyKey |
| 62 | } |
| 63 | return pub, nil |
| 64 | } |
| 65 | |
| 66 | // lengthPrefixed encodes fields so no choice of values makes two lists |
| 67 | // encode the same. |
| 68 | func lengthPrefixed(fields ...string) []byte { |
| 69 | var out []byte |
| 70 | for _, f := range fields { |
| 71 | out = binary.BigEndian.AppendUint32(out, uint32(len(f))) |
| 72 | out = append(out, f...) |
| 73 | } |
| 74 | return out |
| 75 | } |
| 76 | |
| 77 | func chunkAAD(id string, seq int64, stream string, last bool) []byte { |
| 78 | l := "0" |
| 79 | if last { |
| 80 | l = "1" |
| 81 | } |
| 82 | return lengthPrefixed(Purpose, "chunk", id, strconv.FormatInt(seq, 10), stream, l) |
| 83 | } |
| 84 | |
| 85 | func summaryAAD(id string) []byte { return lengthPrefixed(Purpose, "summary", id) } |
| 86 | |
| 87 | func gcmFor(shared []byte) (cipher.AEAD, error) { |
| 88 | key := make([]byte, 32) |
| 89 | if _, err := io.ReadFull(hkdf.New(sha256.New, shared, nil, []byte(Purpose)), key); err != nil { |
| 90 | return nil, err |
| 91 | } |
| 92 | block, err := aes.NewCipher(key) |
| 93 | if err != nil { |
| 94 | return nil, err |
| 95 | } |
| 96 | return cipher.NewGCM(block) |
| 97 | } |
| 98 | |
| 99 | func seal(pub *ecdh.PublicKey, aad, plain []byte) ([]byte, error) { |
| 100 | eph, err := ecdh.P256().GenerateKey(randReader) |
| 101 | if err != nil { |
| 102 | return nil, err |
| 103 | } |
| 104 | nonce := make([]byte, sealNonceLen) |
| 105 | if _, err := io.ReadFull(randReader, nonce); err != nil { |
| 106 | return nil, err |
| 107 | } |
| 108 | shared, err := eph.ECDH(pub) |
| 109 | if err != nil { |
| 110 | return nil, err |
| 111 | } |
| 112 | gcm, err := gcmFor(shared) |
| 113 | if err != nil { |
| 114 | return nil, err |
| 115 | } |
| 116 | out := make([]byte, 0, SealOverhead+len(plain)) |
| 117 | out = append(out, sealPrefix...) |
| 118 | out = append(out, eph.PublicKey().Bytes()...) |
| 119 | out = append(out, nonce...) |
| 120 | return gcm.Seal(out, nonce, plain, aad), nil |
| 121 | } |
| 122 | |
| 123 | func open(priv *ecdh.PrivateKey, aad, sealed []byte) ([]byte, error) { |
| 124 | if len(sealed) < SealOverhead || string(sealed[:len(sealPrefix)]) != sealPrefix { |
| 125 | return nil, ErrSeal |
| 126 | } |
| 127 | body := sealed[len(sealPrefix):] |
| 128 | ephPub, err := ecdh.P256().NewPublicKey(body[:sealEphLen]) |
| 129 | if err != nil { |
| 130 | return nil, ErrSeal |
| 131 | } |
| 132 | shared, err := priv.ECDH(ephPub) |
| 133 | if err != nil { |
| 134 | return nil, ErrSeal |
| 135 | } |
| 136 | gcm, err := gcmFor(shared) |
| 137 | if err != nil { |
| 138 | return nil, ErrSeal |
| 139 | } |
| 140 | plain, err := gcm.Open(nil, body[sealEphLen:sealEphLen+sealNonceLen], body[sealEphLen+sealNonceLen:], aad) |
| 141 | if err != nil { |
| 142 | return nil, ErrSeal |
| 143 | } |
| 144 | return plain, nil |
| 145 | } |
| 146 | |
| 147 | // SealChunk seals one chunk of a read's output: bound to the read, its |
| 148 | // sequence number, its stream and whether it is the last. |
| 149 | func SealChunk(pub *ecdh.PublicKey, id string, seq int64, stream string, last bool, plain []byte) ([]byte, error) { |
| 150 | return seal(pub, chunkAAD(id, seq, stream, last), plain) |
| 151 | } |
| 152 | |
| 153 | func OpenChunk(priv *ecdh.PrivateKey, id string, seq int64, stream string, last bool, sealed []byte) ([]byte, error) { |
| 154 | return open(priv, chunkAAD(id, seq, stream, last), sealed) |
| 155 | } |
| 156 | |
| 157 | // SealSummary seals the result's summary (base64, it rides in result.json). |
| 158 | func SealSummary(pub *ecdh.PublicKey, id string, s Summary) (string, error) { |
| 159 | raw, err := json.Marshal(s) |
| 160 | if err != nil { |
| 161 | return "", err |
| 162 | } |
| 163 | sealed, err := seal(pub, summaryAAD(id), raw) |
| 164 | if err != nil { |
| 165 | return "", err |
| 166 | } |
| 167 | return base64.StdEncoding.EncodeToString(sealed), nil |
| 168 | } |
| 169 | |
| 170 | func OpenSummary(priv *ecdh.PrivateKey, id, sealed string) (Summary, error) { |
| 171 | raw, err := base64.StdEncoding.Strict().DecodeString(sealed) |
| 172 | if err != nil { |
| 173 | return Summary{}, ErrSeal |
| 174 | } |
| 175 | plain, err := open(priv, summaryAAD(id), raw) |
| 176 | if err != nil { |
| 177 | return Summary{}, err |
| 178 | } |
| 179 | var s Summary |
| 180 | if err := json.Unmarshal(plain, &s); err != nil { |
| 181 | return Summary{}, ErrSeal |
| 182 | } |
| 183 | return s, nil |
| 184 | } |
| 185 | |
amadan