In log lines where CN of a cert is used - replace it with cert's SerialNumber

[draychev]

To reduce the risk of logging sensitive data, we need to edit log lines where we log the CommonName of a certificate and need to replace it with the cert's SerialNumber.

Here is a search result pointing to some of these log lines:

• https://github.com/openservicemesh/osm/search?q=%22with+CN%22&type=code

Alternatively another way to find these could be: grep -Iir "log\." $(find . -name '*.go') | grep -i 'CN' --color | grep '%s'
Another search: grep -Iir "log\." $(find . -name '*.go') | grep -i 'GetCommonName' --color

It would be good to tweak these log messages and indicate that what we are logging is the certificate's SerialNumber. With this context we can reference it to other OSM components.

For example the message in this log line:

osm/pkg/envoy/ads/stream.go

Line 160 in ee1ce5e

log.Info().Msgf("Broadcast update received for %s", proxy.GetCommonName())

Should be changed to Broadcast update received for certificate with SerialNumber %s. For this we would need to use GetSerialNumber() from the Certificater interface instead of GetCommonName()

Note: please ensure that all cert issuers have GetSerialNumber() properly implemented (vs just a placeholder): #2312