Implement v2 client GET functionality

api/clients/codecs/polynomial_form.go

@@ -0,0 +1,12 @@
+package codecs
+
+// PolynomialForm is an enum that represents the different ways that a blob polynomial may be represented
+type PolynomialForm uint
+
+const (
+	// Eval is short for "evaluation form". The field elements represent the evaluation at the polynomial's expanded
+	// roots of unity
+	Eval PolynomialForm = iota
+	// Coeff is short for "coefficient form". The field elements represent the coefficients of the polynomial
+	Coeff
+)

api/clients/v2/config.go

@@ -0,0 +1,26 @@
+package clients
+
+import (
+	"time"
+
+	"github.com/Layr-Labs/eigenda/api/clients/codecs"
+)
+
+// EigenDAClientConfig contains configuration values for EigenDAClient
+type EigenDAClientConfig struct {
+	// The blob encoding version to use when writing and reading blobs
+	BlobEncodingVersion codecs.BlobEncodingVersion
+
+	// BlobPolynomialForm is the form that the blob polynomial is commited to and dispersed in, as well as the form the
+	// blob polynomial will be received in from the relay.
+	//
+	// The chosen form dictates how the KZG commitment made to the blob can be used. If the polynomial is in Coeff form
+	// when committed to, then it will be possible to open points on the KZG commitment to prove that the field elements
+	// correspond to the commitment. If the polynomial is in Eval form when committed to, then it will not be possible
+	// to create a commitment opening: the blob will need to be supplied in its entirety to perform a verification that
+	// any part of the data matches the KZG commitment.
+	BlobPolynomialForm codecs.PolynomialForm
+
+	// The timeout duration for relay calls
+	RelayTimeout time.Duration
+}

api/clients/v2/eigenda_client.go

@@ -0,0 +1,229 @@
+package clients
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"math/rand"
+
+	"github.com/Layr-Labs/eigenda/api/clients/codecs"
+	"github.com/Layr-Labs/eigenda/api/clients/v2/verification"
+	core "github.com/Layr-Labs/eigenda/core/v2"
+	"github.com/Layr-Labs/eigensdk-go/logging"
+	"github.com/consensys/gnark-crypto/ecc/bn254"
+)
+
+// EigenDAClient provides the ability to get payloads from the relay subsystem, and to send new payloads to the disperser.
+//
+// This struct is not threadsafe.
+type EigenDAClient struct {
+	log logging.Logger
+	// doesn't need to be cryptographically secure, as it's only used to distribute load across relays
+	random      *rand.Rand
+	config      *EigenDAClientConfig
+	codec       codecs.BlobCodec
+	relayClient RelayClient
+	g1Srs       []bn254.G1Affine
+}
+
+// BuildEigenDAClient builds an EigenDAClient from config structs.
+func BuildEigenDAClient(
+	log logging.Logger,
+	config *EigenDAClientConfig,
+	relayClientConfig *RelayClientConfig,
+	g1Srs []bn254.G1Affine) (*EigenDAClient, error) {
+
+	relayClient, err := NewRelayClient(relayClientConfig, log)
+	if err != nil {
+		return nil, fmt.Errorf("new relay client: %w", err)
+	}
+
+	codec, err := createCodec(config)
+	if err != nil {
+		return nil, err
+	}
+
+	return NewEigenDAClient(log, rand.New(rand.NewSource(rand.Int63())), config, relayClient, codec, g1Srs)
+}
+
+// NewEigenDAClient assembles an EigenDAClient from subcomponents that have already been constructed and initialized.
+func NewEigenDAClient(
+	log logging.Logger,
+	random *rand.Rand,
+	config *EigenDAClientConfig,
+	relayClient RelayClient,
+	codec codecs.BlobCodec,
+	g1Srs []bn254.G1Affine) (*EigenDAClient, error) {
+
+	return &EigenDAClient{
+		log:         log,
+		random:      random,
+		config:      config,
+		codec:       codec,
+		relayClient: relayClient,
+		g1Srs:       g1Srs,
+	}, nil
+}
+
+// GetPayload iteratively attempts to fetch a given blob with key blobKey from relays that have it, as claimed by the
+// blob certificate. The relays are attempted in random order.
+//
+// If the blob is successfully retrieved, then the blob is verified. If the verification succeeds, the blob is decoded
+// to yield the payload (the original user data), and the payload is returned.
+func (c *EigenDAClient) GetPayload(
+	ctx context.Context,
+	blobKey core.BlobKey,
+	blobCertificate *core.BlobCertificate) ([]byte, error) {
+
+	relayKeys := blobCertificate.RelayKeys
+	relayKeyCount := len(relayKeys)
+
+	if relayKeyCount == 0 {
+		return nil, errors.New("relay key count is zero")
+	}
+
+	// create a randomized array of indices, so that it isn't always the first relay in the list which gets hit
+	indices := c.random.Perm(relayKeyCount)
+
+	// TODO (litt3): consider creating a utility which can deprioritize relays that fail to respond (or respond maliciously)
+
+	// iterate over relays in random order, until we are able to get the blob from someone
+	for _, val := range indices {
+		relayKey := relayKeys[val]
+
+		blob, err := c.getBlobWithTimeout(ctx, relayKey, blobKey)
+
+		// if GetBlob returned an error, try calling a different relay
+		if err != nil {
+			c.log.Warn("blob couldn't be retrieved from relay", "blobKey", blobKey, "relayKey", relayKey, "error", err)
+			continue
+		}
+
+		// An honest relay should never send a blob which doesn't verify
+		if !c.verifyBlobFromRelay(blobKey, relayKey, blob, blobCertificate) {
+			// specifics are logged in verifyBlobFromRelay
+			continue
+		}
+
+		payload, err := c.codec.DecodeBlob(blob)
+		if err != nil {
+			c.log.Error(
+				`Blob verification was successful, but decode blob failed!
+					This is likely a problem with the local blob codec configuration,
+					but could potentially indicate a maliciously generated blob certificate.
+					It should not be possible for an honestly generated certificate to verify
+					for an invalid blob!`,
+				"blobKey", blobKey, "relayKey", relayKey, "blobCertificate", blobCertificate, "error", err)
+			return nil, fmt.Errorf("decode blob: %w", err)
+		}
+
+		return payload, nil
+	}
+
+	return nil, fmt.Errorf("unable to retrieve blob %v from any relay. relay count: %d", blobKey, relayKeyCount)
+}
+
+// verifyBlobFromRelay performs the necessary verification after having retrieved a blob from a relay.
+//
+// If all verifications succeed, the method returns true. Otherwise, it logs a warning and returns false.
+func (c *EigenDAClient) verifyBlobFromRelay(
+	blobKey core.BlobKey,
+	relayKey core.RelayKey,
+	blob []byte,
+	blobCertificate *core.BlobCertificate) bool {
+
+	// An honest relay should never send an empty blob
+	if len(blob) == 0 {
+		c.log.Warn("blob received from relay had length 0", "blobKey", blobKey, "relayKey", relayKey)
+		return false
+	}
+
+	blobCommitments := blobCertificate.BlobHeader.BlobCommitments
+
+	// TODO: in the future, this will be optimized to use fiat shamir transformation for verification, rather than
+	//  regenerating the commitment: https://github.com/Layr-Labs/eigenda/issues/1037
+	valid, err := verification.GenerateAndCompareBlobCommitment(c.g1Srs, blob, blobCommitments.Commitment)
+	if err != nil {
+		c.log.Warn(
+			"error generating commitment from received blob",
+			"blobKey", blobKey, "relayKey", relayKey, "error", err)
+		return false
+	}
+
+	if !valid {
+		c.log.Warn(
+			"blob commitment is invalid for received bytes",
+			"blobKey", blobKey, "relayKey", relayKey)
+		return false
+	}
+
+	// Checking that the length returned by the relay is <= the length claimed in the BlobCommitments is sufficient
+	// here: it isn't necessary to verify the length proof itself, since this will have been done by DA nodes prior to
+	// signing for availability.
+	//
+	// Note that the length in the commitment is the length of the blob, padded to a power of 2. For this reason, we
+	// assert <=, as opposed to asserting equality
+	if uint(len(blob)) > blobCommitments.Length {
+		c.log.Warn(
+			"blob length is greater than length claimed in blob commitments",
+			"blobKey", blobKey, "relayKey", relayKey, "blobLength", len(blob),
+			"blobCommitments.Length", blobCommitments.Length)
+		return false
+	}
+
+	// TODO: call verifyBlobV2
+
+	return true
+}
+
+// getBlobWithTimeout attempts to get a blob from a given relay, and times out based on config.RelayTimeout
+func (c *EigenDAClient) getBlobWithTimeout(
+	ctx context.Context,
+	relayKey core.RelayKey,
+	blobKey core.BlobKey) ([]byte, error) {
+
+	timeoutCtx, cancel := context.WithTimeout(ctx, c.config.RelayTimeout)
+	defer cancel()
+
+	return c.relayClient.GetBlob(timeoutCtx, relayKey, blobKey)
+}
+
+// GetCodec returns the codec the client uses for encoding and decoding blobs
+func (c *EigenDAClient) GetCodec() codecs.BlobCodec {
+	return c.codec
+}
+
+// Close is responsible for calling close on all internal clients. This method will do its best to close all internal
+// clients, even if some closes fail.
+//
+// Any and all errors returned from closing internal clients will be joined and returned.
+//
+// This method should only be called once.
+func (c *EigenDAClient) Close() error {
+	relayClientErr := c.relayClient.Close()
+
+	// TODO: this is using join, since there will be more subcomponents requiring closing after adding PUT functionality
+	return errors.Join(relayClientErr)
+}
+
+// createCodec creates the codec based on client config values
+func createCodec(config *EigenDAClientConfig) (codecs.BlobCodec, error) {
+	lowLevelCodec, err := codecs.BlobEncodingVersionToCodec(config.BlobEncodingVersion)
+	if err != nil {
+		return nil, fmt.Errorf("create low level codec: %w", err)
+	}
+
+	switch config.BlobPolynomialForm {
+	case codecs.Eval:
+		// a blob polynomial is already in Eval form after being encoded. Therefore, we use the NoIFFTCodec, which
+		// doesn't do any further conversion.
+		return codecs.NewNoIFFTCodec(lowLevelCodec), nil
+	case codecs.Coeff:
+		// a blob polynomial starts in Eval form after being encoded. Therefore, we use the IFFT codec to transform
+		// the blob into Coeff form after initial encoding. This codec also transforms the Coeff form received from the
+		// relay back into Eval form when decoding.
+		return codecs.NewIFFTCodec(lowLevelCodec), nil
+	default:
+		return nil, fmt.Errorf("unsupported polynomial form: %d", config.BlobPolynomialForm)
+	}
+}

api/clients/v2/mock/relay_client.go

@@ -19,7 +19,7 @@ func NewRelayClient() *MockRelayClient {
 }
 
 func (c *MockRelayClient) GetBlob(ctx context.Context, relayKey corev2.RelayKey, blobKey corev2.BlobKey) ([]byte, error) {
-	args := c.Called(blobKey)
+	args := c.Called(ctx, relayKey, blobKey)
 	if args.Get(0) == nil {
 		return nil, args.Error(1)
 	}