Trying to create a Private Key and Certificate Request with Bouncycastle .net

https://stackoverflow.com/questions/22880772

28-06-2023
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Pregunta

I am trying to create a tool for the people in my company to easily create a private key and a certificate request that I can sign with our inhouse CA. Creating the Certificate Request and signing it works good (Using easy-rsa and Openssl on a CentOS server). But When testing the key created OpenSSL is not able to load the key...

I am using BouncyCastle with VB.Net and this code:

Private Sub cmdGenerate_Click(sender As Object, e As EventArgs) Handles cmdGenerate.Click
    Dim c = Me.Cursor
    Me.Cursor = Cursors.WaitCursor
    Dim rsa As New Crypto.Generators.RsaKeyPairGenerator()
    rsa.Init(New Crypto.KeyGenerationParameters(New Security.SecureRandom, 2048))
    Dim keyPair = rsa.GenerateKeyPair
    Dim Name As String = "Richard"
    Dim Folder As String = "C:"
    Dim filename_csr = Folder & "\" & Name & ".csr"
    Dim filename_key = Folder & "\" & Name & ".key"

    'CSR Request
    Dim x509Navn As New Asn1.X509.X509Name("CN=" & txtNavn.Text)
    Dim csr = New Pkcs.Pkcs10CertificationRequest("SHA1WITHRSA", x509Navn, keyPair.Public, Nothing, keyPair.Private)

    Dim IO As New FileStream(filename_csr, FileMode.Create, FileAccess.Write)
    Dim pemWr As New PemWriter(New StreamWriter(IO))
    Dim pemObj As New Utilities.IO.Pem.PemObject("CERTIFICATE REQUEST", csr.GetEncoded())
    pemWr.WriteObject(pemObj)
    pemWr.Writer.Close()

    'Private key
    IO = New FileStream(filename_key, FileMode.Create, FileAccess.Write)
    pemWr = New PemWriter(New StreamWriter(IO))
    Dim priv As Parameters.RsaPrivateCrtKeyParameters = keyPair.Private
    Dim pStruct As RsaPublicKeyStructure = New RsaPublicKeyStructure(priv.Modulus, priv.Exponent)
    pStruct.ToAsn1Object().GetDerEncoded()
    pemObj = New Utilities.IO.Pem.PemObject("PRIVATE KEY", pStruct.ToAsn1Object().GetDerEncoded())
    pemWr.WriteObject(pemObj)
    pemWr.Writer.Close()

    'Show the files
    Process.Start("explorer.exe", "/select," & filename_csr)

    Me.Cursor = c
End Sub

With these imports:

Imports Org.BouncyCastle
Imports Org.BouncyCastle.Pkcs
Imports Org.BouncyCastle.Asn1.Pkcs
Imports Org.BouncyCastle.Asn1.X509
Imports Org.BouncyCastle.X509
Imports Org.BouncyCastle.Crypto
Imports Org.BouncyCastle.Security
Imports Org.BouncyCastle.OpenSsl
Imports System.Text
Imports System.IO

What I notice is that the private key seems wery small compared to keys created with easy-rsa/openssl Here is a sample privatekey/csr

And the Private Key:

Error messages returned by OpenSSL when trying to decrypt a file is this:

# openssl smime -decrypt -binary -in test.txt.enc -out test.txt -aes256 -recip stackoverflow.crt -inkey stackoverflow.key
unable to load signing key file
139728669665096:error:0D0680A8:asn1 encoding routines:ASN1_CHECK_TLEN:wrong tag:tasn_dec.c:1319:
139728669665096:error:0D07803A:asn1 encoding routines:ASN1_ITEM_EX_D2I:nested asn1 error:tasn_dec.c:381:Type=X509_ALGOR
139728669665096:error:0D08303A:asn1 encoding routines:ASN1_TEMPLATE_NOEXP_D2I:nested asn1 error:tasn_dec.c:751:Field=pkeyalg, Type=PKCS8_PRIV_KEY_INFO
139728669665096:error:0907B00D:PEM routines:PEM_READ_BIO_PRIVATEKEY:ASN1 lib:pem_pkey.c:132:

Command when encrypting file:

# openssl smime -encrypt -binary -in test.txt -out test.txt.enc -aes256 stackoverflow.crt

Best Regards, Richard Hagen

Solución

I solved the issue with Pkcs8Generator.Generate() instead of creating my own PemObject, works like a charm! :D

    'Private key
    Dim pkcs8 As New OpenSsl.Pkcs8Generator(keyPair.Private)
    IO = New FileStream(filename_key, FileMode.Create, FileAccess.Write)
    pemWr = New PemWriter(New StreamWriter(IO))
    pemWr.WriteObject(pkcs8.Generate())
    pemWr.Writer.Close()

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