wolfSSH support for using TPM based key for authentication

[aidangarske]

Description

wolfSSH tpm support using client side public key authentication with rsa. Code working just like the non tpm public key authentication.with rsa

Testing

Just SSH

For ssh public key auth with rsa use ./examples/echoserver/echoserver and for client side use the command:

./examples/client/client -u hansel -i ./keys/hansel-key-rsa.der -j ./keys/hansel-key-rsa.pub

With TPM

For tpm based public key auth with rsa use a tpm simulator and ./examples/echoserver/echoserver and for client use the command:

./examples/client/client -i ../wolfTPM/keyblob.bin -u hansel

Note: refer to the README for detailed build steps and further information.

[dgarske]

Various errors building without TPM:

src/ssh.c:1810:15: error: call to undeclared function 'wc_PubKeyPemToDer'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
        ret = wc_PubKeyPemToDer(in, inSz, newKey, newKeySz);
              ^
src/ssh.c:1810:15: note: did you mean 'wc_KeyPemToDer'?
/Users/runner/work/wolfssh/wolfssh/build-dir/include/wolfssl/wolfcrypt/asn_public.h:692:21: note: 'wc_KeyPemToDer' declared here
    WOLFSSL_API int wc_KeyPemToDer(const unsigned char* pem, int pemSz,
                    ^
1 error generated.
make[1]: *** [src/libwolfssh_la-ssh.lo] Error 1
make[1]: *** Waiting for unfinished jobs....
src/internal.c:12950:25: error: unused variable 'sigSz' [-Werror,-Wunused-variable]
                    int sigSz;
                        ^
1 error generated.

[dgarske]

This PR is very close to ready. Let's change it to use endorsement primary key are parent to avoid the SRK handle/auth.

[dgarske]

The SRK handle and password being hard coded is not good. Both of these should be macros wrapped with #ifndef at a minimum. Ideally they would be arguments to the example client or not needed at all.

If I were writing this example I would create the key using the endorsement primary key... then you would not need anything related to the SRK... It's a pretty easy change, mostly to your README.md to create the key under the endorsement hierarchy using -eh.