Introduced ENABLE_ENCRYPTION flag, ON by default.

[ethouris]

Fixes #666

This introduces the compile option for encryption (cmake: SRT_ENABLE_ENCRYPTION=OFF, configure: --disable-encryption). When used:

• haicrypt subproject is not added to SRT
• SSL library dependencies are off
• setting a password or pbkeylen is not enabled (setting an empty password is tolerated and ignored)
• strict encryption works as before - when off, it allows connections from a password-requiring site

[maxsharabayko]

@ethouris Can you please check that when two peers have different encryption build definition, the expected behavior is respected.
E.g. two srt-live-transmit instances. One built with encryption enabled, the second- with the encryption disabled.
Caller with encryption enabled. Listener with encryption disabled.

Caller		Listener	Connection
no strict	no pwd	no strict	established
no strict	no pwd	strict	established
no strict	pwd	no strict	established
no strict	pwd	strict	rejected

[ethouris]

@ethouris Can you please check that when two peers have different encryption build definition, the expected behavior is respected.
E.g. two srt-live-transmit instances. One built with encryption enabled, the second- with the encryption disabled.
Caller with encryption enabled. Listener with encryption disabled.

Caller Listener Connection
no strict no pwd no strict established
no strict no pwd strict established
no strict pwd no strict established
no strict pwd strict rejected

According to what I have tested, the only case when it matters is when you have one side with encryption supported and configured, and the other side with encryption unsupported. The current state is that with such a combination you need to have both sides strict encryption off, otherwise the connection is rejected.

[maxsharabayko]

@ethouris

According to what I have tested,

Please specify which cases you've tested.

[ethouris]

@ethouris

According to what I have tested,

Please specify which cases you've tested.

1. Listener/NOENC vs. Caller/ENC+password - all combinations of STRICTENC flag.
2. Caller/NOENC vs. Listener/ENC+password - asabov
3. Any NOENC+password -> error in the beginning, as expected

[hgs-gmicros]

Disabling the encryption throws an error and ends the build configuration.

Running: ./configure --disable-encryption

Throws the following error:
No SOURCES given to target: haicrypt_virtual

It appears that this issue should not be labeled as DONE. Not sure is it requires a separate issue.

[maxsharabayko]

Hi @hgs-gmicros
Thanks for reporting. Could you please create an issue for that?