panic: nil pointer dereference in ScanTLS on v0.2.2 when scanning some TLS targets

[PINguin1412]

Hi,

I encountered a crash while using RealiTLScanner v0.2.2.

The scanner successfully connects to the target and prints TLS information, but then crashes with a nil pointer dereference inside ScanTLS.

Output:

time=2026-05-26T14:33:09.505Z level=INFO msg="Connected to target" feasible=true ip=79.137.196.197 origin=79.137.196.197 tls="TLS 1.3" alpn=h2 curve=X25519 cert-length="2719(certs count: 3)" cert-signature=ECDSA-SHA256 cert-publickey=ECDSA cert-domain=github.com cert-issuer="Sectigo Limited" geo=N/A

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x90 pc=0x67f844]

goroutine 10 [running]:
main.ScanTLS(...)
/home/yu/go/src/github.com/xtls/RealiTLScanner/scanner.go:89

Environment:

OS: Linux
RealiTLScanner: v0.2.2

It looks like leaf may become nil before accessing fields like:

leaf.SignatureAlgorithm.String()
leaf.PublicKeyAlgorithm.String()

Maybe a nil check is needed before using leaf.

The issue seems reproducible on some TLS targets with specific certificate chains.

Thanks.