Added support for ExpressPay and EcobankPay EMV QR codes and fixed so…

…me validation issues.

- Added test for 5 live EMV QR codes that failed to be parsed but are actually valid.
- Fixed merchant information tag ID range validation, it can be from 2 to 51 and it's even extracted in that range.
- Fixed validation failures when there is no additional data or merchant language template (both are optional).
- Fixed Issue juanroman-zz#2 by checking there is available length to substring before attempting it.
- Fixed some code analysis warnings.
- Assume if the merchant information has no child nodes (not a child TLV) then the Globally Unique Identifier IS the string, this sis the case for Visa and MasterCard PAN/Alias/Card Numbers present in actual EMV QR codes.

Issue juanroman-zz#2

src/StandardizedQR/MerchantPayload.cs

@@ -245,7 +245,7 @@ public IEnumerable<ValidationResult> Validate(ValidationContext validationContex
 
                 if (null != MerchantAccountInformation && 1 <= MerchantAccountInformation.Count)
                 {
-                    var invalidIdentifiers = MerchantAccountInformation.Keys.Count(k => k < 26 || k > 51);
+                    var invalidIdentifiers = MerchantAccountInformation.Keys.Count(k => k < 2 || k > 51);
                     if (0 < invalidIdentifiers)
                     {
                         errors.Add(new ValidationResult(LibraryResources.MerchantAccountInformationInvalidIdentifier, new string[] { nameof(MerchantAccountInformation) }));

src/StandardizedQR/Services/Decoding/MerchantDecoder.cs

@@ -45,6 +45,28 @@ public MerchantPayload BuildPayload(ICollection<Tlv> tlvs)
             DecodeAccountInformation(tlvs, merchantPayload);
             DecodeUnreservedTemplate(tlvs, merchantPayload);
 
+            // Before validation we can remove additional data and the merchant language template if no data for them was available.
+            // They are optional fields but if they are not populated then validation fails.
+            if (null == merchantPayload.AdditionalData.AdditionalConsumerDataRequest
+                && null == merchantPayload.AdditionalData.BillNumber
+                && null == merchantPayload.AdditionalData.CustomerLabel
+                && null == merchantPayload.AdditionalData.LoyaltyNumber
+                && null == merchantPayload.AdditionalData.MobileNumber
+                && null == merchantPayload.AdditionalData.PurposeOfTransaction
+                && null == merchantPayload.AdditionalData.ReferenceLabel
+                && null == merchantPayload.AdditionalData.StoreLabel
+                && null == merchantPayload.AdditionalData.TerminalLabel)
+            {
+                merchantPayload.AdditionalData = null;
+            }
+
+            if (null == merchantPayload.MerchantInformation.LanguagePreference
+                && null == merchantPayload.MerchantInformation.MerchantCityAlternateLanguage
+                && null == merchantPayload.MerchantInformation.MerchantNameAlternateLanguage)
+            {
+                merchantPayload.MerchantInformation = null;
+            }
+
             return merchantPayload;
         }
 
@@ -96,6 +118,11 @@ private void ParseTLVs(string data, ICollection<Tlv> tlvs)
                 }
                 index += 2;
 
+                if (data.Length - 4 < length)
+                {
+                  break;
+                }
+
                 var value = data.Substring(index, length);
                 index += length - 1;
 
@@ -140,22 +167,32 @@ private void DecodeAccountInformation(ICollection<Tlv> tlvs, MerchantPayload mer
                 foreach (var tlv in merchantAccountInfoTlvs)
                 {
                     var accountInfo = new MerchantAccountInformation();
-                    var globalUniqueIdentifierTlv = tlv.ChildNodes.FirstOrDefault(t => t.Tag == 0);
-                    if (null != globalUniqueIdentifierTlv)
+
+                    // Visa and MasterCard simply have card numbers in their reserved space (02 and 04 for example - Issue #2).
+                    // If there are no child nodes, then the data for this tag is not a TLV string, we could probably assume it's the GlobalUniqueIdentifier since it's a required field.
+                    if (!tlv.ChildNodes.Any())
                     {
-                        accountInfo.GlobalUniqueIdentifier = globalUniqueIdentifierTlv.Value;
+                        accountInfo.GlobalUniqueIdentifier = tlv.Value;
                     }
-
-                    var paymentNetworkSpecificTlvs = tlv.ChildNodes.Where(e => e.Tag >= 1 && e.Tag <= 99);
-                    if (paymentNetworkSpecificTlvs.Any())
+                    else
                     {
-                        accountInfo.PaymentNetworkSpecific = new Dictionary<int, string>();
-                        foreach (var item in paymentNetworkSpecificTlvs)
+                        var globalUniqueIdentifierTlv = tlv.ChildNodes.FirstOrDefault(t => t.Tag == 0);
+                        if (null != globalUniqueIdentifierTlv)
                         {
-                            accountInfo.PaymentNetworkSpecific.Add(item.Tag, item.Value);
+                            accountInfo.GlobalUniqueIdentifier = globalUniqueIdentifierTlv.Value;
+
+                            var paymentNetworkSpecificTlvs = tlv.ChildNodes.Where(e => e.Tag >= 1 && e.Tag <= 99);
+                            if (paymentNetworkSpecificTlvs.Any())
+                            {
+                                accountInfo.PaymentNetworkSpecific = new Dictionary<int, string>();
+                                foreach (var item in paymentNetworkSpecificTlvs)
+                                {
+                                    accountInfo.PaymentNetworkSpecific.Add(item.Tag, item.Value);
+                                }
+                            }
                         }
                     }
-
+                    
                     merchantPayload.MerchantAccountInformation.Add(tlv.Tag, accountInfo);
                 }
             }
@@ -174,19 +211,19 @@ private void DecodeUnreservedTemplate(ICollection<Tlv> tlvs, MerchantPayload mer
                     if (null != globalUniqueIdentifierTlv)
                     {
                         unreservedTemplate.GlobalUniqueIdentifier = globalUniqueIdentifierTlv.Value;
-                    }
 
-                    var contextSpecificTlvs = tlv.ChildNodes.Where(e => e.Tag >= 1 && e.Tag <= 99);
-                    if (contextSpecificTlvs.Any())
-                    {
-                        unreservedTemplate.ContextSpecificData = new Dictionary<int, string>();
-                        foreach (var item in contextSpecificTlvs)
+                        var contextSpecificTlvs = tlv.ChildNodes.Where(e => e.Tag >= 1 && e.Tag <= 99);
+                        if (contextSpecificTlvs.Any())
                         {
-                            unreservedTemplate.ContextSpecificData.Add(item.Tag, item.Value);
+                            unreservedTemplate.ContextSpecificData = new Dictionary<int, string>();
+                            foreach (var item in contextSpecificTlvs)
+                            {
+                                unreservedTemplate.ContextSpecificData.Add(item.Tag, item.Value);
+                            }
                         }
-                    }
 
-                    merchantPayload.UnreservedTemplate.Add(tlv.Tag, unreservedTemplate);
+                        merchantPayload.UnreservedTemplate.Add(tlv.Tag, unreservedTemplate);
+                    }
                 }
             }
         }

src/StandardizedQR/Services/Encoding/IPayloadEncoding.cs

@@ -2,6 +2,6 @@
 {
     public interface IPayloadEncoding<T>
     {
-        string GeneratePayload(T instance);
+        string GeneratePayload(T payload);
     }
 }

src/StandardizedQR/Services/Encoding/MerchantEncoder.cs

@@ -94,7 +94,7 @@ public string GeneratePayload(MerchantPayload payload)
              * ID, Length and Value, to be included in the QR Code, in their respective order, as well as the ID and Length of 
              * the CRC itself (but excluding its Value).
              */
-            sb.Append("6304"); // {id:63}{length:04}
+            sb.Append("6304"); //// {id:63}{length:04}
             var crc16ccittFalseParameters = CrcStdParams.StandartParameters[CrcAlgorithms.Crc16CcittFalse];
             var crc = new Crc(crc16ccittFalseParameters).ComputeHash(System.Text.Encoding.UTF8.GetBytes(sb.ToString()));
             sb.Append(crc.ToHex(true).GetLast(4));
@@ -115,15 +115,16 @@ private string EncodeProperty<T>(PropertyInfo property, T propertyValue)
             var emvSpecAttribute = (EmvSpecificationAttribute)property
                 .GetCustomAttributes(typeof(EmvSpecificationAttribute), false)
                 .First();
-
-            string id = emvSpecAttribute.Id.ToString("D2");
+
             string value = EncodePropertyValue(propertyValue);
-            string length = value.Length.ToString("D2");
-
+
             if (string.IsNullOrWhiteSpace(value))
             {
                 return string.Empty;
             }
+
+            string id = emvSpecAttribute.Id.ToString("D2");
+            string length = value.Length.ToString("D2");
 
             return $"{id}{length}{value}";
         }

src/StandardizedQR/Validation/ValidateObjectAttribute.cs

@@ -1,14 +1,16 @@
-using System.Collections.Generic;
+using System;
+using System.Collections.Generic;
 using System.ComponentModel.DataAnnotations;
 using System.Globalization;
 
 namespace StandardizedQR.Validation
 {
-    /// <summary>
-    /// Helper attribute that allows for recursive valdation using data annotations.
-    /// </summary>
-    /// <seealso cref="ValidationAttribute" />
-    public class ValidateObjectAttribute : ValidationAttribute
+  [AttributeUsage(AttributeTargets.All, AllowMultiple = false)]
+  /// <summary>
+  /// Helper attribute that allows for recursive validation using data annotations.
+  /// </summary>
+  /// <seealso cref="ValidationAttribute" />
+  public class ValidateObjectAttribute : ValidationAttribute
     {
         /// <summary>
         /// Returns true if ... is valid.

test/StandardizedQR.XUnitTests/MerchantPayloadUnitTests.cs

@@ -94,6 +94,115 @@ public void DecodeQR()
             Assert.Equal("12345678", payload.UnreservedTemplate[91].ContextSpecificData[7]);
         }
 
+        [Fact]
+        public void DecodeQR1()
+        {
+            var qrData = "0002010102110213404587173785204155326311010619815204829953039365802GH5909CIB GHANA6005ACCRA622407088656730603088656730663041437";
+            var payload = MerchantPayload.FromQR(qrData);
+
+            Assert.Equal(1, payload.PayloadFormatIndicator);
+            Assert.Equal(11, payload.PointOfInitializationMethod);
+            Assert.Equal("1437", payload.CRC);
+            Assert.Equal(8299, payload.MerchantCategoryCode);
+            Assert.Equal(936, payload.TransactionCurrency);
+            Assert.Equal("CIB GHANA", payload.MerchantName);
+            Assert.Equal("ACCRA", payload.MerchantCity);
+            Assert.Equal("GH", payload.CountyCode);
+
+            Assert.Equal("4045871737852", payload.MerchantAccountInformation[2].GlobalUniqueIdentifier);
+            Assert.Equal("532631101061981", payload.MerchantAccountInformation[4].GlobalUniqueIdentifier);
+
+            Assert.Equal("86567306", payload.AdditionalData.StoreLabel);
+            Assert.Equal("86567306", payload.AdditionalData.TerminalLabel);
+        }
+
+        [Fact]
+        public void DecodeQR2()
+        {
+            var qrData = "0002010102110213404587194150404155326311017361105204581153039365802GH5913SUSAN ALLOTEY6005ACCRA622407080407330503080407330563049EE4";
+            var payload = MerchantPayload.FromQR(qrData);
+
+            Assert.Equal(1, payload.PayloadFormatIndicator);
+            Assert.Equal(11, payload.PointOfInitializationMethod);
+            Assert.Equal("9EE4", payload.CRC);
+            Assert.Equal(5811, payload.MerchantCategoryCode);
+            Assert.Equal(936, payload.TransactionCurrency);
+            Assert.Equal("SUSAN ALLOTEY", payload.MerchantName);
+            Assert.Equal("ACCRA", payload.MerchantCity);
+            Assert.Equal("GH", payload.CountyCode);
+
+            Assert.Equal("4045871941504", payload.MerchantAccountInformation[2].GlobalUniqueIdentifier);
+            Assert.Equal("532631101736110", payload.MerchantAccountInformation[4].GlobalUniqueIdentifier);
+
+            Assert.Equal("04073305", payload.AdditionalData.StoreLabel);
+            Assert.Equal("04073305", payload.AdditionalData.TerminalLabel);
+        }
+
+        [Fact]
+        public void DecodeQR3()
+        {
+            var qrData = "0002010102110213404587568745904155326311155509945204625353039365802GH5915MAXMART LIMITED6005ACCRA62240708620037450308620037456304C913";
+            var payload = MerchantPayload.FromQR(qrData);
+
+            Assert.Equal(1, payload.PayloadFormatIndicator);
+            Assert.Equal(11, payload.PointOfInitializationMethod);
+            Assert.Equal("C913", payload.CRC);
+            Assert.Equal(6253, payload.MerchantCategoryCode);
+            Assert.Equal(936, payload.TransactionCurrency);
+            Assert.Equal("MAXMART LIMITED", payload.MerchantName);
+            Assert.Equal("ACCRA", payload.MerchantCity);
+            Assert.Equal("GH", payload.CountyCode);
+
+            Assert.Equal("4045875687459", payload.MerchantAccountInformation[2].GlobalUniqueIdentifier);
+            Assert.Equal("532631115550994", payload.MerchantAccountInformation[4].GlobalUniqueIdentifier);
+
+            Assert.Equal("62003745", payload.AdditionalData.StoreLabel);
+            Assert.Equal("62003745", payload.AdditionalData.TerminalLabel);
+        }
+
+        [Fact]
+        public void DecodeQR4()
+        {
+            var qrData = "0002010102110213404587793527804155326311019494035204529553039365802GH5915JULITET LIMITED6005ACCRA62240708324313220308324313226304A5FA";
+            var payload = MerchantPayload.FromQR(qrData);
+
+            Assert.Equal(1, payload.PayloadFormatIndicator);
+            Assert.Equal(11, payload.PointOfInitializationMethod);
+            Assert.Equal("A5FA", payload.CRC);
+            Assert.Equal(5295, payload.MerchantCategoryCode);
+            Assert.Equal(936, payload.TransactionCurrency);
+            Assert.Equal("JULITET LIMITED", payload.MerchantName);
+            Assert.Equal("ACCRA", payload.MerchantCity);
+            Assert.Equal("GH", payload.CountyCode);
+
+            Assert.Equal("4045877935278", payload.MerchantAccountInformation[2].GlobalUniqueIdentifier);
+            Assert.Equal("532631101949403", payload.MerchantAccountInformation[4].GlobalUniqueIdentifier);
+
+            Assert.Equal("32431322", payload.AdditionalData.StoreLabel);
+            Assert.Equal("32431322", payload.AdditionalData.TerminalLabel);
+        }
+
+        [Fact]
+        public void DecodeQR5()
+        {
+            var qrData = "00020101021102154382871085619335204541153039365802GH5907PANDORA6005Accra63049C22";
+            var payload = MerchantPayload.FromQR(qrData);
+
+            Assert.Equal(1, payload.PayloadFormatIndicator);
+            Assert.Equal(11, payload.PointOfInitializationMethod);
+            Assert.Equal("9C22", payload.CRC);
+            Assert.Equal(5411, payload.MerchantCategoryCode);
+            Assert.Equal(936, payload.TransactionCurrency);
+            Assert.Equal("PANDORA", payload.MerchantName);
+            Assert.Equal("Accra", payload.MerchantCity);
+            Assert.Equal("GH", payload.CountyCode);
+
+            Assert.True(payload.MerchantAccountInformation.Count == 1);
+            Assert.Equal("438287108561933", payload.MerchantAccountInformation[2].GlobalUniqueIdentifier);
+
+            Assert.Null(payload.AdditionalData);
+        }
+
         [Fact]
         public void PayloadWithSpecificationSample()
         {
@@ -213,7 +322,7 @@ public void InvalidMerchantAccountInformationIdentifiers()
                     MerchantCity = "Mexico City",
                 };
 
-                var payload = merchantPayload.GeneratePayload();
+                merchantPayload.GeneratePayload();
             });
         }
 
@@ -245,7 +354,7 @@ public void InvalidMerchantAccountInformationPaymentSpecificItems()
                     MerchantCity = "Mexico City",
                 };
 
-                var payload = merchantPayload.GeneratePayload();
+                merchantPayload.GeneratePayload();
             });
         }
 
@@ -269,7 +378,7 @@ public void InvalidPayloadFormatIndicator()
                     MerchantCity = "Mexico City",
                 };
 
-                var payload = merchantPayload.GeneratePayload();
+                merchantPayload.GeneratePayload();
             });
         }
 
@@ -294,7 +403,7 @@ public void InvalidTipOrConvenienceIndicator()
                     TipOrConvenienceIndicator = 5
                 };
 
-                var payload = merchantPayload.GeneratePayload();
+                merchantPayload.GeneratePayload();
             });
         }
 
@@ -319,7 +428,7 @@ public void MissingFixedTip()
                     TipOrConvenienceIndicator = 2
                 };
 
-                var payload = merchantPayload.GeneratePayload();
+                merchantPayload.GeneratePayload();
             });
         }
 
@@ -344,7 +453,7 @@ public void MissingPercentageTip()
                     TipOrConvenienceIndicator = 3
                 };
 
-                var payload = merchantPayload.GeneratePayload();
+                merchantPayload.GeneratePayload();
             });
         }
     }