Hello,
I am working on the Port-knocking concept and i have implemented fwknop that uses Single Packet Authorization. The problem is that i don't understand how the data is encoded and how the authenticity and integrity are guaranteed. I don't understand the role of HMAC, key, digest, SHA256, Rijndael, etc.
That is the output of a test command that shows the data in the SPA packet (don't worry it is a model in personal VMs for tests) :
SPA Field Values:
Random Value: 3055038011819845
Username: ubuntu
Timestamp: 1611964357
FKO Version: 2.0.1
Message Type: 1 (Access msg)
Message String: 192.168.1.2,tcp/22
Nat Access:
Server Auth:
Client Timeout: 0
Digest Type: 3 (SHA256)
HMAC Type: 3 (SHA256)
Encryption Type: 1 (Rijndael)
Encryption Mode: 2 (CBC)
Encoded Data: 3055038011819845:dWJ1bnR1:1611964357:2.0.1:1:MTkyLjE2OC4xLjIsdGNwLzIy
SPA Data Digest: Xu/qpfdp8H3Pgx2wzrbtQG7FK/CtR+yTu5LKZI/QH9o
HMAC: Fw6Jk+3OiDS3A/Ac9t93OSYfBgLWOmIP8CrtmgZYoXg
Final SPA Data: /b3WwdTEqEPUYZnJ+z0mrdSNtY1MiYkjrfCKVmnfcl+2U6PHD0g6wvYBvaW4duys14iuG+Lk+9NNSFHEiCI8XJA5BkZHcru1tCg8s8Rd+sjn/w+TmKsqZMf0QIUuTis+XqECyhlrvcwOQ/nDlJCirBj8rFK2ms2DcDBt4GuOgh0KwZR2EYXJuY
I am working on the Port-knocking concept and i have implemented fwknop that uses Single Packet Authorization. The problem is that i don't understand how the data is encoded and how the authenticity and integrity are guaranteed. I don't understand the role of HMAC, key, digest, SHA256, Rijndael, etc.
That is the output of a test command that shows the data in the SPA packet (don't worry it is a model in personal VMs for tests) :
SPA Field Values:
Random Value: 3055038011819845
Username: ubuntu
Timestamp: 1611964357
FKO Version: 2.0.1
Message Type: 1 (Access msg)
Message String: 192.168.1.2,tcp/22
Nat Access:
Server Auth:
Client Timeout: 0
Digest Type: 3 (SHA256)
HMAC Type: 3 (SHA256)
Encryption Type: 1 (Rijndael)
Encryption Mode: 2 (CBC)
Encoded Data: 3055038011819845:dWJ1bnR1:1611964357:2.0.1:1:MTkyLjE2OC4xLjIsdGNwLzIy
SPA Data Digest: Xu/qpfdp8H3Pgx2wzrbtQG7FK/CtR+yTu5LKZI/QH9o
HMAC: Fw6Jk+3OiDS3A/Ac9t93OSYfBgLWOmIP8CrtmgZYoXg
Final SPA Data: /b3WwdTEqEPUYZnJ+z0mrdSNtY1MiYkjrfCKVmnfcl+2U6PHD0g6wvYBvaW4duys14iuG+Lk+9NNSFHEiCI8XJA5BkZHcru1tCg8s8Rd+sjn/w+TmKsqZMf0QIUuTis+XqECyhlrvcwOQ/nDlJCirBj8rFK2ms2DcDBt4GuOgh0KwZR2EYXJuY