Lecture 3.1: Handling Remote Access: RADIUS Motivation

More documents

Recommendations

Info

emote RADIUS server (or other AAA e.g. Cisco TACACS+) TACACS+ Frequently from different ISP: Typical Proxy usage is roaming Giuseppe Bianchi Proxy Operation RADIUS server May be transparent or not transparent (e.g. change response to fit with local policies) ISP Message exchange (example example) Giuseppe Bianchi If needed 4
packet format Code: type of radius packet 1 Access-Request Identifier: match requests with responses IP src and UDP src also help matching Length 2 3 Access-Accept Access-Reject minimum 20, maximum 4096 4 Accounting-Request Authenticator: used to authenticate reply from server Used in user password-hiding algorithm Attributes: extensible information field 5 11 Accounting-Response Access-Challenge Turned out not being extensible enough with “only” 256 types… type len value ……… type len value code 1 byte identifier 1 byte length 2 byte IP header UDP header RADIUS PACKET Giuseppe Bianchi authenticator 16 byte Code (dec) Packet attributes *** Packet authentication Request Authenticator In Access-Request (CS) 16 randomly generated bytes unpredictable and unique (over the lifetime of shared C/S secret) » To avoid replay attack Response Authenticator In Access-Accept/Reject/Challenge packets (SC) One-way MD5 hash of the request authenticator, the shared secret, the packet response information » Response packet is signed! Otherwise packet tampering possible! Specifically: MD5(Code | ID | Length | RequestAuth | Attributes | Secret) Giuseppe Bianchi 5
Page 1 and 2: Giuseppe Bianchi Lecture 3.1: Handl
Page 3: RADIUS Security features Per-packet
Page 7 and 8: Native User-Password Step 1: paddin
Page 9 and 10: PPP CHAP support with RADIUS CHAP
Page 11 and 12: Properties of a good hash function
Page 13 and 14: Message digest size Must be conside
Page 15 and 16: RADIUS Security Weaknesses Recommen
Page 17 and 18: Attack to shared secret based on Us
Page 19 and 20: poor PRNG implementations Attack to
Page 21 and 22: Giuseppe Bianchi Giuseppe Bianchi A
Page 23 and 24: Why “duplicating duplicating”
Page 25: Diameter improvements at a glance /

Lecture 3.1: Handling Remote Access: RADIUS Motivation

Create successful ePaper yourself

Delete template?

Save as template?