SSH Set Allowed Algorithms

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Demonstrates explicitly setting the algorithms allowed during SSH connection negotiation. A JsonObject supplies comma-separated allow-lists for the kex, hostKey, cipher, and mac categories, in order of preference, and is applied before connecting.

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

-- Important: See this note about string length limitations for strings returned by sp_OAMethod calls.
--
CREATE PROCEDURE ChilkatSample
AS
BEGIN
    DECLARE @hr int
    DECLARE @sTmp0 nvarchar(4000)
    DECLARE @success int
    SELECT @success = 0

    --  This example requires the Chilkat API to have been previously unlocked.
    --  See Global Unlock Sample for sample code.

    --  Demonstrates explicitly setting the algorithms allowed during SSH connection negotiation.
    --  
    --  -------------------------------------------------------------------------------------------
    --  Note: You typically should NOT explicitly set allowed algorithms.
    --  By default, Chilkat orders algorithms according to best practices and accounts for known
    --  vulnerabilities such as the "Terrapin Attack".  Hard-coding algorithms makes an application
    --  brittle over time: if a server later changes its allowed algorithms, or if you connect to a
    --  different server, the client and server may fail to agree on a mutually supported set.
    --  -------------------------------------------------------------------------------------------

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

    DECLARE @json int
    EXEC @hr = sp_OACreate 'Chilkat.JsonObject', @json OUT

    --  Algorithms supported by Chilkat, by category:
    --  
    --  Key-exchange:  curve25519-sha256, curve25519-sha256@libssh.org, ecdh-sha2-nistp256,
    --    ecdh-sha2-nistp384, ecdh-sha2-nistp521, diffie-hellman-group14-sha256,
    --    diffie-hellman-group16-sha512, diffie-hellman-group18-sha512,
    --    diffie-hellman-group-exchange-sha256, diffie-hellman-group1-sha1,
    --    diffie-hellman-group14-sha1, diffie-hellman-group-exchange-sha1
    --  
    --  Host key:  ssh-ed25519, ecdsa-sha2-nistp256, ecdsa-sha2-nistp384, ecdsa-sha2-nistp521,
    --    rsa-sha2-256, rsa-sha2-512, ssh-rsa, ssh-dss
    --  
    --  Cipher:  chacha20-poly1305@openssh.com, aes128-ctr, aes256-ctr, aes192-ctr, aes128-cbc,
    --    aes256-cbc, aes192-cbc, aes128-gcm@openssh.com, aes256-gcm@openssh.com, twofish256-cbc,
    --    twofish128-cbc, blowfish-cbc
    --  
    --  MAC:  hmac-sha2-256, hmac-sha2-512, hmac-sha2-256-etm@openssh.com,
    --    hmac-sha2-512-etm@openssh.com, hmac-sha1-etm@openssh.com, hmac-sha1, hmac-ripemd160,
    --    hmac-sha1-96, hmac-md5

    --  List the allowed algorithms for each category, in order of preference.
    DECLARE @allowed_kex nvarchar(4000)
    SELECT @allowed_kex = 'curve25519-sha256@libssh.org,ecdh-sha2-nistp256'
    DECLARE @allowed_hostKey nvarchar(4000)
    SELECT @allowed_hostKey = 'ssh-ed25519,ecdsa-sha2-nistp256'
    DECLARE @allowed_cipher nvarchar(4000)
    SELECT @allowed_cipher = 'chacha20-poly1305@openssh.com,aes256-ctr'
    DECLARE @allowed_mac nvarchar(4000)
    SELECT @allowed_mac = 'hmac-sha2-256,hmac-sha2-512'

    EXEC sp_OAMethod @json, 'UpdateString', @success OUT, 'kex', @allowed_kex
    EXEC sp_OAMethod @json, 'UpdateString', @success OUT, 'hostKey', @allowed_hostKey
    EXEC sp_OAMethod @json, 'UpdateString', @success OUT, 'cipher', @allowed_cipher
    EXEC sp_OAMethod @json, 'UpdateString', @success OUT, 'mac', @allowed_mac

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

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


    PRINT 'Connected.'

    EXEC sp_OAMethod @ssh, 'Disconnect', NULL

    EXEC @hr = sp_OADestroy @ssh
    EXEC @hr = sp_OADestroy @json


END
GO