SQL Server

SSH Tunnel Set Allowed SSH Algorithms

Demonstrates the Chilkat SshTunnel.SetAllowedAlgorithms method, which restricts the SSH connection to a specific set of algorithms. A JsonObject supplies comma-separated allow-lists for the kex, hostKey, cipher, and mac categories. It must be called before Connect.

Important: You typically should not set allowed algorithms explicitly. By default Chilkat orders algorithms according to best practices and accounts for known vulnerabilities.

Background: SSH negotiates a mutually supported algorithm from each category at connection time, and pinning that choice makes an application brittle: if the server later drops a weak algorithm, the two sides may fail to agree and the tunnel stops working. The legitimate reasons to override are a security policy mandating specific algorithms or a compatibility problem with an old server; otherwise let the library's defaults evolve with current guidance.

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SQL Server

--
CREATE PROCEDURE ChilkatSample
AS
BEGIN
    DECLARE @hr int
    DECLARE @sTmp0 nvarchar(4000)
    DECLARE @success int
    SELECT @success = 0

    --  Demonstrates the SshTunnel.SetAllowedAlgorithms method, which restricts the SSH connection to a
    --  specific set of algorithms.  The only argument is a JsonObject.  It must be called before
    --  Connect.
    --  
    --  Note: You typically should NOT set allowed algorithms explicitly.  By default Chilkat orders
    --  algorithms according to best practices and accounts for known vulnerabilities.  Hard-coding
    --  them can make an application brittle if a server later changes its allowed algorithms.

    DECLARE @tunnel int
    EXEC @hr = sp_OACreate 'Chilkat.SshTunnel', @tunnel OUT
    IF @hr <> 0
    BEGIN
        PRINT 'Failed to create ActiveX component'
        RETURN
    END

    --  List the allowed algorithms for each category, in order of preference.
    DECLARE @json int
    EXEC @hr = sp_OACreate 'Chilkat.JsonObject', @json OUT

    EXEC sp_OAMethod @json, 'UpdateString', @success OUT, 'kex', 'curve25519-sha256@libssh.org,ecdh-sha2-nistp256'
    EXEC sp_OAMethod @json, 'UpdateString', @success OUT, 'hostKey', 'ssh-ed25519,ecdsa-sha2-nistp256'
    EXEC sp_OAMethod @json, 'UpdateString', @success OUT, 'cipher', 'chacha20-poly1305@openssh.com,aes256-ctr'
    EXEC sp_OAMethod @json, 'UpdateString', @success OUT, 'mac', 'hmac-sha2-256,hmac-sha2-512'

    --  Apply the allow-list before connecting.
    EXEC sp_OAMethod @tunnel, 'SetAllowedAlgorithms', @success OUT, @json
    IF @success = 0
      BEGIN
        EXEC sp_OAGetProperty @tunnel, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @tunnel
        EXEC @hr = sp_OADestroy @json
        RETURN
      END

    EXEC sp_OASetProperty @tunnel, 'DestHostname', 'db.internal.example.com'
    EXEC sp_OASetProperty @tunnel, 'DestPort', 5432

    DECLARE @sshPort int
    SELECT @sshPort = 22
    EXEC sp_OAMethod @tunnel, 'Connect', @success OUT, 'ssh.example.com', @sshPort
    IF @success = 0
      BEGIN
        EXEC sp_OAGetProperty @tunnel, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @tunnel
        EXEC @hr = sp_OADestroy @json
        RETURN
      END

    PRINT 'Connected.'

    DECLARE @waitForThreadExit int
    SELECT @waitForThreadExit = 1
    EXEC sp_OAMethod @tunnel, 'CloseTunnel', @success OUT, @waitForThreadExit
    IF @success = 0
      BEGIN
        EXEC sp_OAGetProperty @tunnel, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @tunnel
        EXEC @hr = sp_OADestroy @json
        RETURN
      END

    EXEC @hr = sp_OADestroy @tunnel
    EXEC @hr = sp_OADestroy @json


END
GO