VB.NETでのProduct Advertising API 署名認証 - アウトプットしながら学ぶ

VB.NETでのAmazonのProduct Advertising API 署名認証してみました。
PA-APIとも言います。
PA-API経由で売上が発生しないと、PA-APIを使用することができなくなります。

いろいろなサンプルとかあるけど、VB.NETの完全なサンプル見つからないし、
わかりにくかったので、情報集めて、動くようにしました。
Amazonが署名認証導入してから、ハマっている人たくさんいそう。

VS.NET2008で作ってます。
まず、System.WEBを参照に追加。
次に以下のモジュールを追加

Module ModuleAmazonAPI
    Dim sAssociateTag As String = "[アソシエイトタグ]"
    Dim sAccessKeyId As String = "[アクセスキーID]"
    Dim sSecretAccessKey As String = "[シークレットアクセスキー]"
    Public Function MakeAmazonRequest( _
    ByVal sAssociateTag As String, _
    ByVal sAccessKeyId As String, _
    ByVal sSecretAccessKey As String, _
    ByVal sSearchKeyWord As String) As String

        Dim dictRequest As New Dictionary(Of String, String)
        'リクエストパラメータをハッシュテーブルに保存
        dictRequest("Service") = "AWSECommerceService"
        dictRequest("Version") = "2008-04-07"
        dictRequest("AssociateTag") = sAssociateTag
        dictRequest("ContentType") = "Text/XML"
        dictRequest("Operation") = "ItemSearch"
        dictRequest("ResponseGroup") = "Small,ItemAttributes, Reviews,EditorialReview,Images,BrowseNodes,SalesRank,Offers"
        dictRequest("AWSAccessKeyId") = sAccessKeyId
        dictRequest("SearchIndex") = "All"
        dictRequest("Keywords") = sSearchKeyWord

        Dim dteNow As DateTime = DateTime.UtcNow
        Dim sTimeStamp As String = dteNow.ToString("yyyy-MM-ddTHH:mm:ssZ")
        'タイムスタンプはGMT
        dictRequest("Timestamp") = sTimeStamp
        Dim pc As New ParamComparer()
        Dim sortedHash As New SortedDictionary(Of String, String)(dictRequest, pc)

        ' Get the canonical query string
        Dim canonicalQS As String = ConstructCanonicalQueryString(sortedHash)

        '以下の部分を追加
        '============================
        'GET
        'ecs.amazonaws.jp
        '/onca/xml
        '============================
        Dim builder As New System.Text.StringBuilder()
        builder.Append("GET").Append(vbLf).Append( _
        CStr("ecs.amazonaws.jp").ToLower()).Append(vbLf). _
        Append("/onca/xml").Append(vbLf).Append(canonicalQS)

        Dim stringToSign As String = builder.ToString()
        Dim toSign As Byte() = System.Text.Encoding.UTF8.GetBytes(stringToSign)

        Dim secret As Byte()
        secret = System.Text.Encoding.UTF8.GetBytes(sSecretAccessKey)
        Dim signer As System.Security.Cryptography.HMAC
        signer = New Security.Cryptography.HMACSHA256(secret)

        Dim sigBytes As Byte() = signer.ComputeHash(toSign)
        Dim signature As String = Convert.ToBase64String(sigBytes)

        Dim qsBuilder As New System.Text.StringBuilder()
        qsBuilder.Append(" http://").Append("ecs.amazonaws.jp"). _
        Append("/onca/xml").Append("?").Append(canonicalQS). _
        Append("&Signature=").Append(PercentEncodeRfc3986(signature))

        Return qsBuilder.ToString()

    End Function

    Private Function PercentEncodeRfc3986(ByVal str As String) As String
        str = System.Web.HttpUtility.UrlEncode(str, System.Text.Encoding.UTF8)
        str = str.Replace("'", "%27").Replace( _
        "(", "%28").Replace(")", "%29").Replace("*", "%2A") _
        .Replace("!", "%21").Replace("%7e", "~").Replace("+", "%20")
        Dim sbuilder As New System.Text.StringBuilder(str)
        For i As Integer = 0 To sbuilder.Length - 1

            If sbuilder(i) = "%"c Then
                'コメント化
                sbuilder(i + 1) = [Char].ToUpper(sbuilder(i + 1)) '日本語対策で追加
                sbuilder(i + 2) = [Char].ToUpper(sbuilder(i + 2))
                'End If
            End If

        Next
        Return sbuilder.ToString()
    End Function
    Private Function ConstructCanonicalQueryString(ByVal sortedParamMap As SortedDictionary(Of String, String)) As String
        Dim builder As New System.Text.StringBuilder()

        If sortedParamMap.Count = 0 Then
            builder.Append("")
            Return builder.ToString()
        End If

        For Each kvp As KeyValuePair(Of String, String) In sortedParamMap

            builder.Append(PercentEncodeRfc3986(kvp.Key))
            builder.Append("=")
            builder.Append(PercentEncodeRfc3986(kvp.Value))
            builder.Append("&")
        Next
        Dim canonicalString As String = builder.ToString()
        canonicalString = canonicalString.Substring(0, canonicalString.Length - 1)
        Return canonicalString
    End Function

    Class ParamComparer
        Implements IComparer(Of String)
        Public Function Compare(ByVal p1 As String, ByVal p2 As String) As Integer Implements IComparer(Of String).Compare
            Return String.CompareOrdinal(p1, p2)
        End Function
    End Class

End Module

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Module ModuleAmazonAPI

Dim sAssociateTag As String = "[アソシエイトタグ]"

Dim sAccessKeyId As String = "[アクセスキーID]"

Dim sSecretAccessKey As String = "[シークレットアクセスキー]"

Public Function MakeAmazonRequest( _

ByVal sAssociateTag As String, _

ByVal sAccessKeyId As String, _

ByVal sSecretAccessKey As String, _

ByVal sSearchKeyWord As String) As String

Dim dictRequest As New Dictionary(Of String, String)

'リクエストパラメータをハッシュテーブルに保存

dictRequest("Service") = "AWSECommerceService"

dictRequest("Version") = "2008-04-07"

dictRequest("AssociateTag") = sAssociateTag

dictRequest("ContentType") = "Text/XML"

dictRequest("Operation") = "ItemSearch"

dictRequest("ResponseGroup") = "Small,ItemAttributes, Reviews,EditorialReview,Images,BrowseNodes,SalesRank,Offers"

dictRequest("AWSAccessKeyId") = sAccessKeyId

dictRequest("SearchIndex") = "All"

dictRequest("Keywords") = sSearchKeyWord

Dim dteNow As DateTime = DateTime.UtcNow

Dim sTimeStamp As String = dteNow.ToString("yyyy-MM-ddTHH:mm:ssZ")

'タイムスタンプはGMT

dictRequest("Timestamp") = sTimeStamp

Dim pc As New ParamComparer()

Dim sortedHash As New SortedDictionary(Of String, String)(dictRequest, pc)

' Get the canonical query string

Dim canonicalQS As String = ConstructCanonicalQueryString(sortedHash)

'以下の部分を追加

'============================

'GET

'ecs.amazonaws.jp

'/onca/xml

'============================

Dim builder As New System.Text.StringBuilder()

builder.Append("GET").Append(vbLf).Append( _

CStr("ecs.amazonaws.jp").ToLower()).Append(vbLf). _

Append("/onca/xml").Append(vbLf).Append(canonicalQS)

Dim stringToSign As String = builder.ToString()

Dim toSign As Byte() = System.Text.Encoding.UTF8.GetBytes(stringToSign)

Dim secret As Byte()

secret = System.Text.Encoding.UTF8.GetBytes(sSecretAccessKey)

Dim signer As System.Security.Cryptography.HMAC

signer = New Security.Cryptography.HMACSHA256(secret)

Dim sigBytes As Byte() = signer.ComputeHash(toSign)

Dim signature As String = Convert.ToBase64String(sigBytes)

Dim qsBuilder As New System.Text.StringBuilder()

qsBuilder.Append(" http://").Append("ecs.amazonaws.jp"). _

Append("/onca/xml").Append("?").Append(canonicalQS). _

Append("&Signature=").Append(PercentEncodeRfc3986(signature))

Return qsBuilder.ToString()

End Function

Private Function PercentEncodeRfc3986(ByVal str As String) As String

str = System.Web.HttpUtility.UrlEncode(str, System.Text.Encoding.UTF8)

str = str.Replace("'", "%27").Replace( _

"(", "%28").Replace(")", "%29").Replace("*", "%2A") _

.Replace("!", "%21").Replace("%7e", "~").Replace("+", "%20")

Dim sbuilder As New System.Text.StringBuilder(str)

For i As Integer = 0 To sbuilder.Length - 1

If sbuilder(i) = "%"c Then

'コメント化

sbuilder(i + 1) = [Char].ToUpper(sbuilder(i + 1)) '日本語対策で追加

sbuilder(i + 2) = [Char].ToUpper(sbuilder(i + 2))

'End If

End If

Return sbuilder.ToString()

End Function

Private Function ConstructCanonicalQueryString(ByVal sortedParamMap As SortedDictionary(Of String, String)) As String

Dim builder As New System.Text.StringBuilder()

If sortedParamMap.Count = 0 Then

builder.Append("")

Return builder.ToString()

End If

For Each kvp As KeyValuePair(Of String, String) In sortedParamMap

builder.Append(PercentEncodeRfc3986(kvp.Key))

builder.Append("=")

builder.Append(PercentEncodeRfc3986(kvp.Value))

builder.Append("&")

Dim canonicalString As String = builder.ToString()

canonicalString = canonicalString.Substring(0, canonicalString.Length - 1)

Return canonicalString

End Function

Class ParamComparer

Implements IComparer(Of String)

Public Function Compare(ByVal p1 As String, ByVal p2 As String) As Integer Implements IComparer(Of String).Compare

Return String.CompareOrdinal(p1, p2)

End Function

End Class

End Module

使いかたは、

        Dim sAssociateTag As String = "[アソシエイトタグ]"
        Dim sAccessKeyId As String = "[アクセスキーID]"
        Dim sSecretAccessKey As String = "[シークレットアクセスキー]"
        Dim sURL as String
 
        sURL = MakeAmazonRequest(sAssociateTag, sAccessKeyId, sSecretAccessKey, "ラーメンマン")

Dim sAssociateTag As String = "[アソシエイトタグ]"

Dim sAccessKeyId As String = "[アクセスキーID]"

Dim sSecretAccessKey As String = "[シークレットアクセスキー]"

Dim sURL as String

sURL = MakeAmazonRequest(sAssociateTag, sAccessKeyId, sSecretAccessKey, "ラーメンマン")

sURLでアクセスすれば、検索結果を得られます。