From 60417282a404387d562239f17211e67d7f66c17d Mon Sep 17 00:00:00 2001
From: josh <QuestofIranon@users.noreply.github.com>
Date: Sun, 8 Apr 2018 19:38:12 -0700
Subject: [PATCH] verifies p2pkh addresses

---
 baked_in.go       | 48 +++++++++++++++++++++++++++++++++++++++++++++--
 validator_test.go | 15 ++++++++-------
 2 files changed, 54 insertions(+), 9 deletions(-)

diff --git a/baked_in.go b/baked_in.go
index df790d8..55bd4c4 100644
--- a/baked_in.go
+++ b/baked_in.go
@@ -11,6 +11,8 @@ import (
 	"sync"
 	"time"
 	"unicode/utf8"
+	"crypto/sha256"
+	"bytes"
 )
 
 // Func accepts a FieldLevel interface for all validation needs. The return
@@ -398,9 +400,51 @@ func isEthereumAddress(fl FieldLevel) bool {
 
 // IsBitcoinAddress is the validation function for validating if the field's value is a valid btc address, currently only based on the format
 func isBitcoinAddress(fl FieldLevel) bool {
-	field := fl.Field()
+	address := fl.Field().String()
+
+	if btcAddressRegex.MatchString(address) {
+
+		alphabet := []byte("123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz")
+
+		decode := [25]byte{}
+
+		for _, n := range []byte(address) {
+			d := bytes.IndexByte(alphabet, n)
+
+			if(d == -1){
+				return false
+			}
+
+			for i := 24; i >= 0; i-- {
+				d += 58 * int(decode[i])
+				decode[i] = byte(d % 256)
+				d /= 256
+			}
+		}
+
+
+		if decode[0] != 0 {
+			return false
+		}
+
+		h := sha256.New()
+		h.Write(decode[:21])
+		d := h.Sum([]byte{})
+		h = sha256.New()
+		h.Write(d)
+
+		validchecksum := [4]byte{}
+		computedchecksum := [4]byte{}
+
+		copy(computedchecksum[:], h.Sum(d[:0]))
+		copy(validchecksum[:], decode[21:])
+
+		println(address, "::", validchecksum[:], computedchecksum[:])
+
+		return validchecksum == computedchecksum
+	}
 
-	return btcAddressRegex.MatchString(field.String()) || btcAddressRegexBech32.MatchString(field.String())
+	return btcAddressRegexBech32.MatchString(address)
 }
 
 // ExcludesRune is the validation function for validating that the field's value does not contain the rune specified within the param.
diff --git a/validator_test.go b/validator_test.go
index d8be987..c16d426 100644
--- a/validator_test.go
+++ b/validator_test.go
@@ -4446,10 +4446,11 @@ func TestBitcoinAddressValidation(t *testing.T){
 	}{
 		{"", false},
 		{"0x02F9AE5f22EA3fA88F05780B30385bEC", false},
-		{"123f681646d4a755815f9cb19e1acc8565a0c2ac", false},
-		{"1BvBMSEYstWetqTFn5Au4m4GFg7xJaNVN2", true},
-		{"3J98t1WpEZ73CNmQviecrnyiWrnqRhWNLy", true},
-		{"bc1qar0srrr7xfkvy5l643lydnw9re59gtzzwf5mdq", true},
+		{"1A1zP1ePQGefi2DMPTifTL5SLmv7DivfNa", false},
+		{"1BvBMSEYstWetqTFn5Au4m4GFg7xJaNVN2", true}, // valid p2pkh address
+		{"3P14159f73E4gFr7JterCCQh9QjiTjiZrG", true}, // valid p2sh address
+		{"bc1qar0srrr7xfkvy5l643lydnw9re59gtzzwf5mdq", true}, // valid bech32 address
+
 	}
 
 
@@ -4460,15 +4461,15 @@ func TestBitcoinAddressValidation(t *testing.T){
 
 		if test.expected {
 			if !IsEqual(errs, nil) {
-				t.Fatalf("Index: %d btc_addr failed Error: %s", i, errs)
+				t.Fatalf("Index: %d btc_addr failed with Error: %s", i, errs)
 			}
 		} else {
 			if IsEqual(errs, nil) {
-				t.Fatalf("Index: %d btc_addr failed Error: %s", i, errs)
+				t.Fatalf("Index: %d btc_addr failed with Error: %s", i, errs)
 			} else {
 				val := getError(errs, "", "")
 				if val.Tag() != "btc_addr" {
-					t.Fatalf("Index: %d Latitude failed Error: %s", i, errs)
+					t.Fatalf("Index: %d Latitude failed with Error: %s", i, errs)
 				}
 			}
 		}