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comments for mint and wallet packages
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@elnosh
elnosh committed Apr 15, 2024
1 parent 0bd333c commit 8b1a7c5
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Showing 4 changed files with 91 additions and 29 deletions.
2 changes: 2 additions & 0 deletions mint/config.go
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Original file line number Diff line number Diff line change
Expand Up @@ -22,6 +22,8 @@ func GetConfig() Config {
}
}

// getMintInfo returns information about the mint as
// defined in NUT-06: https://github.com/cashubtc/nuts/blob/main/06.md
func getMintInfo() (*nut06.MintInfo, error) {
mintInfo := nut06.MintInfo{
Name: os.Getenv("MINT_NAME"),
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1 change: 1 addition & 0 deletions mint/lightning/lightning.go
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Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,7 @@ const (
LND = "Lnd"
)

// Client interface to interact with a Lightning backend
type Client interface {
CreateInvoice(amount uint64) (Invoice, error)
InvoiceSettled(hash string) bool
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74 changes: 48 additions & 26 deletions mint/mint.go
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Original file line number Diff line number Diff line change
Expand Up @@ -66,6 +66,8 @@ func LoadMint(config Config) (*Mint, error) {
return mint, nil
}

// mintPath returns the mint's path
// at $HOME/.gonuts/mint
func mintPath() string {
homedir, err := os.UserHomeDir()
if err != nil {
Expand All @@ -80,25 +82,21 @@ func mintPath() string {
return path
}

func (m *Mint) KeysetList() []string {
keysetIds := make([]string, len(m.Keysets))

i := 0
for k := range m.Keysets {
keysetIds[i] = k
i++
}
return keysetIds
}

// RequestMintQuote will process a request to mint tokens
// and returns a mint quote response or an error.
// The request to mint a token is explained in
// NUT-04 here: https://github.com/cashubtc/nuts/blob/main/04.md.
func (m *Mint) RequestMintQuote(method string, amount uint64, unit string) (nut04.PostMintQuoteBolt11Response, error) {
// only support bolt11
if method != "bolt11" {
return nut04.PostMintQuoteBolt11Response{}, cashu.PaymentMethodNotSupportedErr
}
// only support sat unit
if unit != "sat" {
return nut04.PostMintQuoteBolt11Response{}, cashu.UnitNotSupportedErr
}

// get an invoice from the lightning backend
invoice, err := m.requestInvoice(amount)
if err != nil {
return nut04.PostMintQuoteBolt11Response{}, err
Expand All @@ -119,6 +117,8 @@ func (m *Mint) RequestMintQuote(method string, amount uint64, unit string) (nut0
return reqMintQuoteResponse, nil
}

// GetMintQuoteState returns the state of a mint quote.
// Used to check whether a mint quote has been paid.
func (m *Mint) GetMintQuoteState(method, quoteId string) (nut04.PostMintQuoteBolt11Response, error) {
if method != "bolt11" {
return nut04.PostMintQuoteBolt11Response{}, cashu.PaymentMethodNotSupportedErr
Expand All @@ -129,6 +129,7 @@ func (m *Mint) GetMintQuoteState(method, quoteId string) (nut04.PostMintQuoteBol
return nut04.PostMintQuoteBolt11Response{}, cashu.InvoiceNotExistErr
}

// check if the invoice has been paid
settled := m.LightningClient.InvoiceSettled(invoice.PaymentHash)
if settled != invoice.Settled {
invoice.Settled = settled
Expand All @@ -140,7 +141,8 @@ func (m *Mint) GetMintQuoteState(method, quoteId string) (nut04.PostMintQuoteBol
return quoteState, nil
}

// id - quote id to lookup invoice
// MintTokens verifies whether the mint quote with id has been paid and proceeds to
// sign the blindedMessages and return the BlindedSignatures if it was paid.
func (m *Mint) MintTokens(method, id string, blindedMessages cashu.BlindedMessages) (cashu.BlindedSignatures, error) {
if method != "bolt11" {
return nil, cashu.PaymentMethodNotSupportedErr
Expand All @@ -164,6 +166,8 @@ func (m *Mint) MintTokens(method, id string, blindedMessages cashu.BlindedMessag
totalAmount += message.Amount
}

// verify that amount from invoice is less than the amount
// from the blinded messages
if totalAmount > invoice.Amount {
return nil, cashu.OutputsOverInvoiceErr
}
Expand All @@ -174,6 +178,7 @@ func (m *Mint) MintTokens(method, id string, blindedMessages cashu.BlindedMessag
return nil, cashu.BuildCashuError(err.Error(), cashu.StandardErrCode)
}

// mark invoice as redeemed after signing the blinded messages
invoice.Settled = true
invoice.Redeemed = true
m.db.SaveInvoice(*invoice)
Expand All @@ -184,13 +189,14 @@ func (m *Mint) MintTokens(method, id string, blindedMessages cashu.BlindedMessag
return blindedSignatures, nil
}

// Swap will process a request to swap tokens.
// A swap requires a set of valid proofs and blinded messages.
// If valid, the mint will sign the blindedMessages and invalidate
// the proofs that were used as input.
// It returns the BlindedSignatures.
func (m *Mint) Swap(proofs cashu.Proofs, blindedMessages cashu.BlindedMessages) (cashu.BlindedSignatures, error) {
var proofsAmount uint64 = 0
var blindedMessagesAmount uint64 = 0

for _, proof := range proofs {
proofsAmount += proof.Amount
}
proofsAmount := proofs.Amount()

for _, msg := range blindedMessages {
blindedMessagesAmount += msg.Amount
Expand All @@ -205,7 +211,8 @@ func (m *Mint) Swap(proofs cashu.Proofs, blindedMessages cashu.BlindedMessages)
return nil, err
}

// if verification complete, sign blinded messages and add used proofs to db
// if verification complete, sign blinded messages and invalidate used proofs
// by adding them to the db
blindedSignatures, err := m.signBlindedMessages(blindedMessages)
if err != nil {
cashuErr := cashu.BuildCashuError(err.Error(), cashu.StandardErrCode)
Expand All @@ -229,6 +236,8 @@ type MeltQuote struct {
Preimage string
}

// MeltRequest will process a request to melt tokens and return a MeltQuote.
// A melt is requested by a wallet to request the mint to pay an invoice.
func (m *Mint) MeltRequest(method, request, unit string) (MeltQuote, error) {
if method != "bolt11" {
return MeltQuote{}, cashu.PaymentMethodNotSupportedErr
Expand All @@ -237,14 +246,15 @@ func (m *Mint) MeltRequest(method, request, unit string) (MeltQuote, error) {
return MeltQuote{}, cashu.UnitNotSupportedErr
}

// generate random id for melt quote
randomBytes := make([]byte, 32)
_, err := rand.Read(randomBytes)
if err != nil {
return MeltQuote{}, fmt.Errorf("melt request error: %v", err)
}

hash := sha256.Sum256(randomBytes)

// Fee reserved that is required by the mint
amount, fee, err := m.LightningClient.FeeReserve(request)
if err != nil {
return MeltQuote{}, fmt.Errorf("error getting fee: %v", err)
Expand All @@ -264,6 +274,8 @@ func (m *Mint) MeltRequest(method, request, unit string) (MeltQuote, error) {
return meltQuote, nil
}

// GetMeltQuoteState returns the state of a melt quote.
// Used to check whether a melt quote has been paid.
func (m *Mint) GetMeltQuoteState(method, quoteId string) (MeltQuote, error) {
if method != "bolt11" {
return MeltQuote{}, cashu.PaymentMethodNotSupportedErr
Expand All @@ -277,6 +289,8 @@ func (m *Mint) GetMeltQuoteState(method, quoteId string) (MeltQuote, error) {
return *meltQuote, nil
}

// MeltTokens verifies whether proofs provided are valid
// and proceeds to attempt payment.
func (m *Mint) MeltTokens(method, quoteId string, proofs cashu.Proofs) (MeltQuote, error) {
if method != "bolt11" {
return MeltQuote{}, cashu.PaymentMethodNotSupportedErr
Expand All @@ -292,22 +306,24 @@ func (m *Mint) MeltTokens(method, quoteId string, proofs cashu.Proofs) (MeltQuot
return MeltQuote{}, cashu.BuildCashuError(err.Error(), cashu.StandardErrCode)
}

var inputsAmount uint64 = 0
for _, input := range proofs {
inputsAmount += input.Amount
}
proofsAmount := proofs.Amount()

if inputsAmount < meltQuote.Amount+meltQuote.FeeReserve {
// checks if amount in proofs is enough
if proofsAmount < meltQuote.Amount+meltQuote.FeeReserve {
return MeltQuote{}, cashu.InsufficientProofsAmount
}

// if proofs are valid, ask the lightning backend
// to make the payment
preimage, err := m.LightningClient.SendPayment(meltQuote.InvoiceRequest)
if err != nil {
return *meltQuote, nil
}

// if payment succeeded, mark melt quote as paid
// and invalidate proofs
meltQuote.Paid = true
meltQuote.Preimage = preimage

for _, proof := range proofs {
m.db.SaveProof(proof)
}
Expand All @@ -317,11 +333,14 @@ func (m *Mint) MeltTokens(method, quoteId string, proofs cashu.Proofs) (MeltQuot

func (m *Mint) VerifyProofs(proofs cashu.Proofs) (bool, error) {
for _, proof := range proofs {
// if proof is already in db, it means it was already used
dbProof := m.db.GetProof(proof.Secret)
if dbProof != nil {
return false, cashu.ProofAlreadyUsedErr
}

// check that id in the proof matches id of any
// of the mint's keyset
var k *secp256k1.PrivateKey
if keyset, ok := m.Keysets[proof.Id]; !ok {
return false, cashu.InvalidKeysetProof
Expand Down Expand Up @@ -350,6 +369,8 @@ func (m *Mint) VerifyProofs(proofs cashu.Proofs) (bool, error) {
return true, nil
}

// signBlindedMessages will sign the blindedMessages and
// return the blindedSignatures
func (m *Mint) signBlindedMessages(blindedMessages cashu.BlindedMessages) (cashu.BlindedSignatures, error) {
blindedSignatures := make(cashu.BlindedSignatures, len(blindedMessages))

Expand Down Expand Up @@ -387,7 +408,8 @@ func (m *Mint) signBlindedMessages(blindedMessages cashu.BlindedMessages) (cashu
return blindedSignatures, nil
}

// creates lightning invoice
// requestInvoices requests an invoice from the Lightning backend
// for the given amount
func (m *Mint) requestInvoice(amount uint64) (*lightning.Invoice, error) {
invoice, err := m.LightningClient.CreateInvoice(amount)
if err != nil {
Expand Down
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