Interperability with Linphone

[Ihor Olkhovskyi]

Hello,

What is the best way to debug the following issue:

Linphone 5.2.5 (Android) <- SRTP -> rtpengine 12.3.1.2

Linphone by default proposing these suites:

AEAD_AES_128_GCM

AEAD_AES_256_GCM

AES_CM_128_HMAC_SHA1_80

AES_CM_265_HMAC_SHA1_80

On answer, RTPengine by default offers

AEAD_AES_128_GCM, 

but the sound is definitely not decoded, I can hear only distorted voice.

When I'm explicitly disabling AEAD_AES_* suites (with SDES-no-XXX), sound is work as expected on negotiated

AES_CM_128_HMAC_SHA1_80

suite

How is the best to find out who's messing with encryption?

Cheers,

Ihor

[Richard Fuchs]

The best way is to pull a pcap and try to manually decode the SRTP, or at least compare the SRTP media to the RTP media. Also comparing the encrypt direction with the decrypt direction can be helpful.

AEAD is a bit of a challenge as there aren't many tools that support it. But you can use rtpengine itself to decrypt or verify AEAD. I have a half-finished and uncommited script sitting here for that very purpose.

Also try disabling just AEAD_AES_128_GCM - perhaps the 256-bit version works?

Feel free to post some sample packets here together with the crypto keys if you need help decrypting/verifying them.

Cheers

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[Ihor Olkhovskyi]

Richard,

I've manage to solve the issue. It's famous SDES-pad. Sorry for the noize!