PureBasic

Get Public Key in Format for ~/.ssh/authorized_keys

See more SSH Key Examples

If you have an RSA private key, then by definition you also have the public key because the RSA public key is a subset of the private key. (The public key is just the modulus + exponent, whereas the private key contains additional items.)

This example converts an RSA private key to the OpenSSH format public-key (a single line of text) that can be inserted into the ~/.ssh/authorized_keys file on the SSH server to enable public-key authentication for a particular private key.

Note: On the SSH server, such as on a Ubuntu Linux computer, the sshd config file is located at /etc/ssh/sshd_config. It contains a line that indicates the authorized keys file, and the typical default is:

AuthorizedKeysFile      .ssh/authorized_keys

PureBasic

IncludeFile "CkStringBuilder.pb"
IncludeFile "CkSshKey.pb"

Procedure ChilkatExample()

    success.i = 0

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

    ; Load a private key from a file.  The format can be text format, such as .ppk (PuTTY private key) or .pem.
    privateKeyPath.s = "/myKeys/myRsaKey.ppk"

    ; Here's an example of a non-encrypted private key in ppk format:

    ; PuTTY-User-Key-File-3: ssh-rsa
    ; Encryption: none
    ; Comment: rsa-key-20220606
    ; Public-Lines: 6
    ; AAAAB3NzaC1yc2EAAAADAQABAAABAQDKQUdx8EU6qIpVcT1NbL/sSnELJdifQa+K
    ; kOqvgKIU30wIwGMfigSeiTFXw2jWsPcMyOIRKUvR3nf8wtR6NEj3qDfGUo3b/8Fx
    ; 5BHDKuR5uU0ZJmv3Am+/hSPWOJFltL8DkxDLEpGDujLwGiUbpD9SADYhhvk9OBA7
    ; 0l70hYs9gWJBjm9CR8hPg3b3F7gOYljAY2dk6W3PGmzQi+D7BTE0yYfhEOoDX7ah
    ; sgrUnWIiIWK9cqLT8XbAb8gitnCmP0LerxRAkX25O4Gx/uGSrMxO/cRwz5UpiNL2
    ; cciM7P4vzlbcpQiKrKaBYg5GB84QqE3xCt9cEr/qD235LpSMnWRR
    ; Private-Lines: 14
    ; AAABAQClKCE7PUSK3c34b3vrmX4vaapdvA3kHjNGJ4g8wAGaoazpCJDo1D9pZgZQ
    ; 8FTP27ohSniwItSzD8NTN5ViJQfglBDXddo5Z+ODKQYIJSJk85etjd5j2i1+ay4U
    ; ZCT2tF22gYUZDpScyJOH1RGwPLMoNtv9DMbB4uH+t46qhdJp6aWvJB7L/HUhnszc
    ; qbwTG//CDL2j8Y1Mre8zvWBA8cr0I0qCzWD/Xw5MgDgpA444CFGpYb1mt8ghLniT
    ; hMGgt6scUO/lnBEYo17a9N7wBexvyk0ZgEVo6nweRnCFHijNbG+C82svrsLQuL7g
    ; o65BcEqLo+wBO+FtutTf2gtevZcBAAAAgQDnt2Freyfn1V93qZar06w7dXn4yV4G
    ; cvQ3FmJBhk7akEFuZPOceDqrAgzS+TmsH4C96ssETdMxMO4vwEjSnZAatw6TKgnK
    ; 9aDJL6/uzhk/dmBmyp7iWttN9QW9cRQvLYtwJssNDPUmF1/1cGFMpLyLfTlRBCok
    ; 8dksYys4FTUfeQAAAIEA33N+LIO8i2U1NNfy2yU5GGJoFaXwPIa/CZNzZ8hbvLwm
    ; 5yay4MKxGgizX+FhQ/OiEiFDEs1GDssKTXaqhE9mI/vKKLGYj9wEiWhwnawx56GI
    ; WhdTZPtWkU4tYj/OkABD8vp973W1k4NEjYxVg8AoZZL1Kr4zturV8KJl9v4b/ZkA
    ; AACBANAijbBLPxSTdyG9duZT89+jIdgjdjVdV5UL/xZLEh6pWbHludZHItXl62G7
    ; luuJbiqhx2FANxhSu7/tAEX3z2jx7ari51Ddf/+sqfrLwc3dPkU8YXpUNYJIaNFR
    ; LyzMMZvL2sPxnE6dxt4nR761y+EnTZpZ2oeSC21Lzq2xKcBp
    ; Private-MAC: e0c3b5eba925944355d8d63fefcec02a982c7281a87e9994c04ce956b5c3e69b

    sbKey.i = CkStringBuilder::ckCreate()
    If sbKey.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success = CkStringBuilder::ckLoadFile(sbKey,privateKeyPath,"utf-8")
    If success = 0
        Debug "Failed to load the private key from a file."
        CkStringBuilder::ckDispose(sbKey)
        ProcedureReturn
    EndIf

    key.i = CkSshKey::ckCreate()
    If key.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    ; If the private key file is encrypted, then you'll need to set a password.
    ; If it's not encrypted, the password here is ignored.
    CkSshKey::setCkPassword(key, "private_key_password")

    ; The FromPuttyPrivateKey method will actually auto-detect the format and correctly load any string-based format.
    ; For example, you can pass in a PEM private key.
    success = CkSshKey::ckFromPuttyPrivateKey(key,CkStringBuilder::ckGetAsString(sbKey))
    If success = 0
        Debug CkSshKey::ckLastErrorText(key)
        CkStringBuilder::ckDispose(sbKey)
        CkSshKey::ckDispose(key)
        ProcedureReturn
    EndIf

    ; Get the public key in OpenSSH format:
    pubKeyStr.s = CkSshKey::ckToOpenSshPublicKey(key)
    Debug pubKeyStr

    ; Sample output:
    ; ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDKQUdx8EU6qIpVcT1NbL/sSnELJdifQa+KkOqvgKIU30wIwGMfigSeiTFXw2jWsPcMyOIRKUvR3nf8wtR6NEj3qDfGUo3b/8Fx5BHDKuR5uU0ZJmv3Am+/hSPWOJFltL8DkxDLEpGDujLwGiUbpD9SADYhhvk9OBA70l70hYs9gWJBjm9CR8hPg3b3F7gOYljAY2dk6W3PGmzQi+D7BTE0yYfhEOoDX7ahsgrUnWIiIWK9cqLT8XbAb8gitnCmP0LerxRAkX25O4Gx/uGSrMxO/cRwz5UpiNL2cciM7P4vzlbcpQiKrKaBYg5GB84QqE3xCt9cEr/qD235LpSMnWRR rsa-key-20220606

    ; To authorize the private key for a particular SSH user account, copy the above public key into the ~/.ssh/authorized_keys file.
    ; If authorized_keys already contains some keys, you can append it to a new line in the file.


    CkStringBuilder::ckDispose(sbKey)
    CkSshKey::ckDispose(key)


    ProcedureReturn
EndProcedure