add secure enclave signatures to local server response #1658
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
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@@ -4,29 +4,45 @@ | |
| package main | ||
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| import ( | ||
| "crypto" | ||
| "crypto/ecdsa" | ||
| "crypto/rand" | ||
| "encoding/base64" | ||
| "encoding/json" | ||
| "errors" | ||
| "fmt" | ||
| "os" | ||
| "time" | ||
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| "github.com/kolide/kit/ulid" | ||
| "github.com/kolide/krypto/pkg/challenge" | ||
| "github.com/kolide/krypto/pkg/echelper" | ||
| "github.com/kolide/krypto/pkg/secureenclave" | ||
| "github.com/kolide/launcher/ee/agent/certs" | ||
| "github.com/kolide/launcher/ee/secureenclavesigner" | ||
| ) | ||
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| const secureEnclaveTimestampValiditySeconds = 10 | ||
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| // runSecureEnclave performs either a create-key operation using the secure enclave. | ||
| // It's available as a separate command because launcher runs as root by default and since it's | ||
| // not in a user security context, it can't use the secure enclave directly. However, this command | ||
| // can be run in the user context using launchctl. | ||
| func runSecureEnclave(args []string) error { | ||
| // currently we are just creating key, but plan to add sign command in future | ||
| if len(args) < 1 { | ||
| return errors.New("not enough arguments, expect create_key | sign") | ||
| } | ||
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| switch args[0] { | ||
| case secureenclavesigner.CreateKeyCmd: | ||
| return createSecureEnclaveKey() | ||
| case secureenclavesigner.SignCmd: | ||
| if len(args) < 2 { | ||
| return errors.New("not enough arguments for sign command, expect sign <data>") | ||
| } | ||
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| return signWithSecureEnclave(args[1]) | ||
| default: | ||
| return fmt.Errorf("unknown command %s", args[0]) | ||
| } | ||
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@@ -46,3 +62,127 @@ func createSecureEnclaveKey() error { | |
| os.Stdout.Write(secureEnclavePubDer) | ||
| return nil | ||
| } | ||
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| func signWithSecureEnclave(signRequestB64 string) error { | ||
| b, err := base64.StdEncoding.DecodeString(signRequestB64) | ||
| if err != nil { | ||
| return fmt.Errorf("decoding b64 sign request: %w", err) | ||
| } | ||
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| var signRequest secureenclavesigner.SignRequest | ||
| if err := json.Unmarshal(b, &signRequest); err != nil { | ||
| return fmt.Errorf("unmarshaling msgpack sign request: %w", err) | ||
| } | ||
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| if err := verifySecureEnclaveChallenge(signRequest); err != nil { | ||
| return fmt.Errorf("verifying challenge: %w", err) | ||
| } | ||
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| userPubKey, err := echelper.PublicB64DerToEcdsaKey(signRequest.UserPubkey) | ||
| if err != nil { | ||
| return fmt.Errorf("marshalling b64 der to public key: %w", err) | ||
| } | ||
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| seSigner, err := secureenclave.New(userPubKey) | ||
| if err != nil { | ||
| return fmt.Errorf("creating secure enclave cmd signer: %w", err) | ||
| } | ||
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| // tag the ends of the data to sign, this is intended to ensure that launcher wont | ||
| // sign arbitrary things, any party verifying the signature will need to | ||
| // handle these tags | ||
| dataToSign := []byte(fmt.Sprintf("kolide:%s:kolide", signRequest.Data)) | ||
|
There was a problem hiding this comment. I think maybe I'm missing something (I will revisit once you've got a diagram available) -- why do we add There was a problem hiding this comment. I created a PR for a doc here https://github.com/kolide/monorepo/pull/166. We have to do it at this point because there is no way to ensure that the process which is execing launcher in the user context adds the tags. The inability for a process to confidently detect it's parent process is the primary driver for all this tag hoopla. |
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| signResponseInner := secureenclavesigner.SignResponseInner{ | ||
| Nonce: fmt.Sprintf("%s%s", signRequest.BaseNonce, ulid.New()), | ||
| Timestamp: time.Now().UTC().Unix(), | ||
| Data: dataToSign, | ||
| } | ||
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| innerResponseBytes, err := json.Marshal(signResponseInner) | ||
| if err != nil { | ||
| return fmt.Errorf("marshalling inner response: %w", err) | ||
| } | ||
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| digest, err := echelper.HashForSignature(innerResponseBytes) | ||
| if err != nil { | ||
| return fmt.Errorf("hashing data for signature: %w", err) | ||
| } | ||
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| sig, err := seSigner.Sign(rand.Reader, digest, crypto.SHA256) | ||
| if err != nil { | ||
| return fmt.Errorf("signing request: %w", err) | ||
| } | ||
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| outerResponseBytes, err := json.Marshal(secureenclavesigner.SignResponseOuter{ | ||
| Msg: innerResponseBytes, | ||
| Sig: sig, | ||
| }) | ||
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| if err != nil { | ||
| return fmt.Errorf("marshalling outer response: %w", err) | ||
| } | ||
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| os.Stdout.Write([]byte(base64.StdEncoding.EncodeToString(outerResponseBytes))) | ||
| return nil | ||
| } | ||
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| func verifySecureEnclaveChallenge(signRequest secureenclavesigner.SignRequest) error { | ||
| challengeUnmarshalled, err := challenge.UnmarshalChallenge(signRequest.Challenge) | ||
| if err != nil { | ||
| return fmt.Errorf("unmarshaling challenge: %w", err) | ||
| } | ||
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| serverPubKey, err := loadSecureEnclaveServerPubKey(string(signRequest.ServerPubKey)) | ||
| if err != nil { | ||
| return fmt.Errorf("loading server public key: %w", err) | ||
| } | ||
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| if err := challengeUnmarshalled.Verify(*serverPubKey); err != nil { | ||
| return fmt.Errorf("verifying challenge: %w", err) | ||
| } | ||
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| // Check the timestamp, this prevents people from saving a challenge and then | ||
| // reusing it a bunch. However, it will fail if the clocks are too far out of sync. | ||
| timestampDelta := time.Now().Unix() - challengeUnmarshalled.Timestamp() | ||
| if timestampDelta > secureEnclaveTimestampValiditySeconds || timestampDelta < -secureEnclaveTimestampValiditySeconds { | ||
| return fmt.Errorf("timestamp delta %d is outside of validity range %d", timestampDelta, secureEnclaveTimestampValiditySeconds) | ||
| } | ||
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| return nil | ||
| } | ||
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| func loadSecureEnclaveServerPubKey(b64Key string) (*ecdsa.PublicKey, error) { | ||
| providedKey, err := echelper.PublicB64DerToEcdsaKey([]byte(b64Key)) | ||
| if err != nil { | ||
| return nil, fmt.Errorf("parsing provided server public key: %w", err) | ||
| } | ||
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| if secureenclavesigner.Undertest { | ||
| if secureenclavesigner.TestServerPubKey == "" { | ||
| return nil, errors.New("test server public key not set") | ||
| } | ||
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| k, err := echelper.PublicB64DerToEcdsaKey([]byte(secureenclavesigner.TestServerPubKey)) | ||
| if err != nil { | ||
| return nil, fmt.Errorf("parsing test server public key: %w", err) | ||
| } | ||
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| if providedKey.Equal(k) { | ||
| return k, nil | ||
| } | ||
| } | ||
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| for _, serverKey := range []string{certs.K2EccServerCert, certs.ReviewEccServerCert, certs.LocalhostEccServerCert} { | ||
| k, err := echelper.PublicPemToEcdsaKey([]byte(serverKey)) | ||
| if err != nil { | ||
| continue | ||
| } | ||
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| if providedKey.Equal(k) { | ||
| return k, nil | ||
| } | ||
| } | ||
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| return nil, errors.New("provided server public key does not match any known server public key") | ||
| } | ||
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