Add fallback if CryptAcquireContext fails with ERROR_ACCESS_DENIED,
as seen in Jenkins CI.
The fallback, also suggested by https://stackoverflow.com/a/14053718/547065,
is to retry with machine-wide key container, if user-specific fails.
The bug happens only when connecting with SSL with client certificates.
Apparently if client certificates are used in TLS handshake,
private keys for cert should be loaded into named persistent
container.This is because AcquireCredentialsHandle is done partically
out-of-process in lsass.exe, and lsass wants to read private keys from disk
See discussion in https://github.com/dotnet/runtime/issues/23749
Schannel has legacy behavior for ephemeral keys, not involving lsass,
and this is why it worked for us so far, however there are limitations.
It appears to only use rsa_sha1 for signature verification, and newer
OpenSSL no longer allows SHA1 for it, and this ends up in
"algorithm mismatch" message from schannel.
The above is just my understanding of how it works, because there is no
real documentation, the conclusion is based on discussion in
https://github.com/dotnet/runtime/issues/23749
The fix:
So storing the key in persistent named container evidently fixes it,
and this is what is done in this patch. Care is takes to destroy
key container after key is no longer needed, to
avoid filling %AppData%\Roaming\Microsoft\Crypto\RSA with tiny encrypted
key files. Thus the "persistency window" of the key in container on disk
is only for duration of AcquireCredentialsHandle
Implement proper verification for server certificate chain,
with refactoring of the certificate stuff.
If custom CA and CRL certs are given, load them into in-memory store, and
use CertVerifyCertificateChainPolicy() to verify the certificate chain.
There are minor errors fixed, such as
- now there is a support for private keys encoded as BEGIN/END PRIVATE KEY
in PEM, instead of only BEGIN/END RSA PRIVATE KEY
- memory leak around CryptAcquireContext() is fixed i.e when client loads
private key, it previously did never released it, not even when connection
ended.
The handling of certificates moved into schannel_certs.c from various places
