Fix not calling the signing callback when using PK callbacks + TLS 1.3.

[kareem-wolfssl]

Description

Fixes zd#18300

Testing

Customer confirmed fix

Checklist

• added tests
• updated/added doxygen
• updated appropriate READMEs
• Updated manual and documentation

[dgarske]

@kareem-wolfssl ,

Fix looks good, but it would be nice if our test cases covered this...

I was able to reproduce the issue with ./configure --enable-pkcallbacks CFLAGS="-DTEST_PK_PRIVKEY -DDEBUG_PK_CB" && make && ./tests/unit.test. And confirmed this fix resolves it... Any idea why that wasn't picked up with our CI?

starting TLSv13 extra cipher suite tests
trying server command line[1001]: SuiteTest -v 4 -l TLS13-CHACHA20-POLY1305-SHA256 -2 -p 0 -P
trying client command line[1002]: SuiteTest -v 4 -l TLS13-CHACHA20-POLY1305-SHA256 -2 -p 62126 -P
PK ECC KeyGen: keySz 32, Curve ID 7
PK ECC KeyGen: ret 0
PK ECC KeyGen: keySz 32, Curve ID 7
PK ECC KeyGen: ret 0
PK HKDF Extract: ret 0 saltLen 0 ikmLen 32
PK ECC PMS: Side server, Peer Curve 7
PK ECC PMS: Side client, Peer Curve 7
PK ECC PMS: ret 0, PubKeySz 65, OutLen 32
PK HKDF Extract: ret 0 saltLen 32 ikmLen 32
Set Encrypt Keys CbSet Encrypt Keys Cb: ret -288
PK ECC PMS: ret 0, PubKeySz 65, OutLen 32
PK HKDF Extract: ret 0 saltLen 0 ikmLen 32
PK HKDF Extract: ret 0 saltLen 32 ikmLen 32
Set Encrypt Keys CbSet Encrypt Keys Cb: ret -288
SSL_accept error -317, need the private key
wolfSSL error: SSL_accept failed
PK RSA Verify: sigSz 256, keySz 270
PK RSA Verify: ret 51

This line args->sigLen = (word16)GetPrivateKeySigSize(ssl); is a copy/paste from the TLS v1.2 code, which existed before the TLS v1.3 code.