Motivation. ⢠The security of the DNS transaction directly depends on the nonce's randomness. ⢠The source port and
Subverting BIND’s SRTT Algorithm Roee Hay IBM
Jonathan Kalechstein
Gabi Nakibly
Technion
National EW Research & Simulation Center
Agenda • Off-path (blind) DNS cache poisoning attacks • BIND’s name server (NS) selection algorithm and previous attacks
• The new attack
Off-Path DNS Cache Poisoning
A Trivial Scenario
DNS Resolver
DNS server
Attacker
A Trivial Scenario
DNS Resolver
DNS server
DNS Query: What is the IP of ibm.com?
Attacker
A Trivial Scenario DNS query: What is the IP of ibm.com?
DNS Resolver
DNS server
Attacker
A Trivial Scenario DNS query: What is the IP of ibm.com?
DNS Resolver
DNS server
Malicious DNS Answer: The IP is 6.6.6.6.
Attacker
A Trivial Scenario DNS query: What is the IP of ibm.com?
DNS Resolver
DNS Answer: The IP is 129.42.60.158.
Malicious DNS Answer: The IP is 6.6.6.6.
DNS server
Attacker
Common Protection Against Off-Path Attacks DNS Query Packet
• Queries • Answers (empty)
UDP
DNS Answer: The IP is 129.42.60.158. • SRC Port • DST Port
• SRC IP address Malicious Answer: • DSTDNS IP address
IP
DNS Resolver
DNS
DNS query: What isis• the what the IP IP of of ibm.com? ibm.com? TXID
The IP is 6.6.6.6.
DNS Randomize server the data
Attacker
Off-path DNS Poisoning: An Actual Attack ibm.com zone NS1
DNS Resolver
NS2
NS3 NS4
Attacker
Off-path DNS Poisoning: An Actual Attack DNS query (DST IP=NS2, TXID=2500, SRC Port = 1200)
DNS Resolver
ibm.com zone NS1 NS2
NS3 NS4
Attacker
Off-path DNS Poisoning: An Actual Attack DNS query (DST IP=NS2, TXID=2500, SRC Port = 1200)
DNS Resolver
ibm.com zone NS1 NS2
NS3 NS4
Malicious spoofed DNS answer (SRC IP=NS2 TXID=2500, DST Port = 1200)
Attacker
Off-path DNS Poisoning: An Actual Attack
DNS Resolver
DNS query (DST IP=NS2, TXID=2500, SRC Port = 1200)
ibm.com zone
DNS answer (SRC IP=NS2, TXID=2500, DST Port = 1200)
NS2
NS1
NS3 NS4
Malicious spoofed DNS answer (SRC IP=NS2 TXID=2500, DST Port = 1200)
Attacker
Motivation • The security of the DNS transaction directly depends on the nonce’s randomness.
DNS Nonce Selected NS Source Port TXID
Motivation • The security of the DNS transaction directly depends on the nonce’s randomness.
DNS Nonce
• The source port and TXID are well studied.
Selected NS Source Port TXID
Motivation • The security of the DNS transaction directly depends on the nonce’s randomness.
DNS Nonce
• The source port and TXID are well studied. • We try to tackle the NS selection. • Derandomizing only the NS selection does not make an off-path attack feasible. It makes existing attacks more efficient, i.e. faster. • It enables on-path (Man-in-the-Middle) attacks if the attacker is on one path between the resolver and the NS, but not on another.
Selected NS Source Port TXID
CDF of the # of NSs (Top-Level Domains only) 1 0.9 0.8 0.7
CDF
0.6 0.5 0.4 0.3 0.2 0.1
0
1
2
3
4
5
6
7
8
9
10
11
# of NSs * Data parsed out of the root’s zone file: http://www.iana.org/domains/root/files
12
13
14
15
16
17
18
19
20
BIND’s NS Selection and Attacks
BIND’s NS Selection: The Smoothed RTT Algorithm • Goal. Choose the most responsive (by Round-Trip Time) NS.
• Problem. RTT changes frequently. • Data structure. A moving average for each NS IP.
• Operations. • • • •
Initialize Update Decay Error
𝑆𝑅𝑇𝑇 ∈ 1,32 𝜇𝑠 𝑆𝑅𝑇𝑇 = 0.7 ⋅ 𝑆𝑅𝑇𝑇𝑜𝑙𝑑 + 0.3 ⋅ 𝑅𝑇𝑇 𝑆𝑅𝑇𝑇 = 0.98 ⋅ 𝑆𝑅𝑇𝑇𝑜𝑙𝑑 𝑆𝑅𝑇𝑇 = min 𝑆𝑅𝑇𝑇𝑜𝑙𝑑 + 200𝑚𝑠, 1𝑠
• Cache. A map keyed only by NS IPs is maintained. • Selection. Candidate NS with lowest SRTT value is queried first.
The SRTT Algorithm: A Potential Vulnerability • The NS selection is derandomized if we can control the SRTT value of the candidates. • Either by: • Increasing all candidates but one • Decreasing the victim NS.
• Since the cache stores all NSs together, maybe we can control it externally by a malicious NS?
Previous Work and our Contribution • [Herzberg & Shulman, 2012] increases the SRTT of all candidates NSs but one by abusing fragmented IP packets.
SRTT ops Initialize Decay
Update Error
Previous Work and our Contribution • [Herzberg & Shulman, 2012] increases the SRTT of all candidates NSs but one by abusing fragmented IP packets. • [Petr, 2009] decreases the SRTT of the victim NS by fast spoofed responses.
SRTT ops Initialize Decay
Update Error
Previous Work and our Contribution • [Herzberg & Shulman, 2012] increases the SRTT of all candidates NSs but one by abusing fragmented IP packets. • [Petr, 2009] decreases the SRTT of the victim NS by fast spoofed responses.
• These attacks are probabilistic.
SRTT ops Initialize Decay
Update Error
Previous Work and our Contribution • [Herzberg & Shulman, 2012] increases the SRTT of all candidates NSs but one by abusing fragmented IP packets. • [Petr, 2009] decreases the SRTT of the victim NS by fast spoofed responses.
• These attacks are probabilistic. • We present a deterministic attack against the Decay and Initialize operations. • Another cool feature: The victim NS does not see our attack.
SRTT ops Initialize Decay
Update Error
The New Attack
General Setting of the Attack
Attacker
The attacker’s control PC
General Setting of the Attack
Attacker
𝐴1
The attacker’s control PC
An attacker’s controlled NS. Authoritative of the a1.foo. domain
General Setting of the Attack
Attacker
The attacker’s control PC
𝐴1
An attacker’s controlled NS. Authoritative of the a1.foo. domain
𝐴2
An attacker’s controlled NS. Authoritative of the a2.foo. domain
General Setting of the Attack ibm.com zone
Attacker
Resolver
V NS
The resolver which we attack
𝐴1
𝐴2
General Setting of the Attack ibm.com zone
Attacker
𝐴1
𝐴2
Resolver
V NS
We lower the SRTT of V on the resolver, thus force it to be selected when resolving ibm.com. The target zone can have an arbitrary amount of authoritative name servers.
General Setting of the Attack ibm.com zone
Attacker
𝐴1
𝐴2
Resolver
V NS
𝑛 non-open NSs which we abuse. Can be anywhere on the Internet. We don’t need to control them.
Resolver’s SRTT Cache
The Attack
WHO
ibm.com zone
Attacker
Resolver
SRTT
OP
V
100000 [U]
NS
90000 [U]
V NS
𝐴1
𝐴2 SRTT Operations [I]nit
[U]date [D]ecay
[E]rror
Resolver’s SRTT Cache
The Attack
WHO
ibm.com zone
Attacker
What is the IP of a2.foo?
Resolver
SRTT
OP
V
100000 [U]
NS
90000 [U]
V NS
𝐴1
𝐴2 SRTT Operations [I]nit
[U]date [D]ecay
[E]rror
Resolver’s SRTT Cache
The Attack
WHO
ibm.com zone
Attacker
What is the IP of a2.foo?
Resolver
V
SRTT
OP
V
100000 [U]
NS
90000 [U]
𝐴2
21
[I]
NS
𝐴1 Next list (SRTT sorted)
𝐴2
𝐴2
SRTT Operations [I]nit
[U]date [D]ecay
[E]rror
Resolver’s SRTT Cache
The Attack
WHO
ibm.com zone
Attacker
Resolver
V
SRTT
OP
V
100000 [U]
NS
90000 [U]
𝐴2
21
[I]
NS
𝐴1 Next list (SRTT sorted)
𝐴2
𝐴2
SRTT Operations [I]nit
[U]date [D]ecay
[E]rror
Resolver’s SRTT Cache
The Attack
WHO
ibm.com zone
Resolver
Attacker
𝐴1
V
SRTT
OP
V
100000 [U]
NS
90000 [U]
𝐴2
21
[I]
NS
What is the IP of a2.foo?
Next list (SRTT sorted)
𝐴2
𝐴2
SRTT Operations [I]nit
[U]date [D]ecay
[E]rror
Resolver’s SRTT Cache
The Attack
WHO
ibm.com zone
Resolver
Attacker
𝐴1
V
SRTT
OP
V
100000 [U]
NS
90000 [U]
𝐴2
10000 [U]
NS
a2.foo is 6.6.6.6.
Next list (SRTT sorted)
𝐴2 SRTT Operations [I]nit
[U]date [D]ecay
[E]rror
Resolver’s SRTT Cache
The Attack
WHO
ibm.com zone
Attacker
a2.foo is 6.6.6.6.
Resolver
V
SRTT
OP
V
100000 [U]
NS
90000 [U]
𝐴2
10000 [U]
NS
𝐴1 Next list (SRTT sorted)
𝐴2 SRTT Operations [I]nit
[U]date [D]ecay
[E]rror
Resolver’s SRTT Cache
The Attack
WHO
ibm.com zone
Attacker
What is the IP of attack.a1.foo?
Resolver
V
SRTT
OP
V
100000 [U]
NS
90000 [U]
𝐴2
10000 [U]
NS
𝐴1 Next list (SRTT sorted)
𝐴2 SRTT Operations [I]nit
[U]date [D]ecay
[E]rror
Resolver’s SRTT Cache
The Attack
WHO
ibm.com zone
Attacker
What is the IP of attack.a1.foo?
Resolver
V
SRTT
OP
V
100000 [U]
NS
90000 [U]
𝐴2
10000 [U]
𝐴1
31
[I]
NS
𝐴1 Next list (SRTT sorted)
𝐴2
𝐴1
SRTT Operations [I]nit
[U]date [D]ecay
[E]rror
Resolver’s SRTT Cache
The Attack
WHO
ibm.com zone
Attacker
Resolver
V
SRTT
OP
V
100000 [U]
NS
90000 [U]
𝐴2
10000 [U]
𝐴1
31
[I]
NS
𝐴1 Next list (SRTT sorted)
𝐴2
𝐴1
SRTT Operations [I]nit
[U]date [D]ecay
[E]rror
Resolver’s SRTT Cache
The Attack
WHO
ibm.com zone
Resolver
Attacker
V
SRTT
OP
V
100000 [U]
NS
90000 [U]
𝐴2
10000 [U]
𝐴1
31
[I]
NS
What is the IP of attack.a1.foo?
𝐴1 Next list (SRTT sorted)
𝐴2
𝐴1
SRTT Operations [I]nit
[U]date [D]ecay
[E]rror
Resolver’s SRTT Cache
The Attack
WHO
ibm.com zone
Resolver
Attacker
𝐴1
V
SRTT
OP
V
100000 [U]
NS
90000 [U]
𝐴2
10000 [U]
𝐴1
78443 [U]
NS
I don’t know ask: 𝐶1 , 𝐶2 , … , 𝐶𝑛 𝐴2 , V
Next list (SRTT sorted)
𝐴2
𝐴1
SRTT Operations [I]nit
[U]date [D]ecay
[E]rror
Resolver’s SRTT Cache
The Attack
WHO
ibm.com zone
Resolver
Attacker
𝐴1
I don’t know ask: 𝐶1 , 𝐶2 , … , 𝐶𝑛 𝐴2 , V
V NS
SRTT
OP
V
100000 [U]
NS
90000 [U]
𝐴2
10000 [U]
𝐴1
78443 [U]
𝐶1
23
[I]
𝐶2
22
[I]
32
[I]
25
[I]
⋮ 𝐶𝑘 ⋮ 𝐶𝑛
Next list (SRTT sorted)
𝐴2
𝐶2
𝐶1
…
𝐶𝑘
𝐴2
V
SRTT Operations [I]nit
[U]date [D]ecay
[E]rror
Resolver’s SRTT Cache
The Attack
WHO
ibm.com zone
Attacker
Resolver
V NS
SRTT
OP
V
100000 [U]
NS
90000 [U]
𝐴2
10000 [U]
𝐴1
78443 [U]
𝐶1
23
[I]
𝐶2
22
[I]
32
[I]
25
[I]
⋮
𝐴1
𝐶𝑘 ⋮ 𝐶𝑛
Next list (SRTT sorted)
𝐴2
𝐶2
𝐶1
…
𝐶𝑘
𝐴2
V
SRTT Operations [I]nit
[U]date [D]ecay
[E]rror
Resolver’s SRTT Cache
The Attack
WHO
ibm.com zone
Attacker
Resolver
V NS
𝐶2 , What is the IP of attack.a1.foo?
𝐴1
SRTT
OP
V
100000 [U]
NS
90000 [U]
𝐴2
10000 [U]
𝐴1
78443 [U]
𝐶1
23
[I]
𝐶2
22
[I]
32
[I]
25
[I]
⋮ 𝐶𝑘 ⋮ 𝐶𝑛
Next list (SRTT sorted)
𝐴2
𝐶2
𝐶1
…
𝐶𝑘
𝐴2
V
SRTT Operations [I]nit
[U]date [D]ecay
[E]rror
Resolver’s SRTT Cache
The Attack
WHO
ibm.com zone
Attacker
Resolver
Query refused.
𝐴1
V NS
SRTT
OP
V
98000 [D]
NS
90000 [U]
𝐴2
9800 [D]
𝐴1
78443 [U]
𝐶1
22 [D]
𝐶2
84341 [U]
⋮ 𝐶𝑘
31 [D]
⋮ 𝐶𝑛
24 [D]
Next list (SRTT sorted)
𝐴2
𝐶2
𝐶1
…
𝐶𝑘
𝐴2
V
SRTT Operations [I]nit
[U]date [D]ecay
[E]rror
Resolver’s SRTT Cache
The Attack
WHO
ibm.com zone
Attacker
Resolver
Query refused.
𝐴1
V NS
SRTT
OP
V
98000 [D]
NS
90000 [U]
𝐴2
9800 [D]
𝐴1
78443 [U]
𝐶1
22 [D]
𝐶2
84341 [U]
⋮ 𝐶𝑘
31 [D]
⋮ 𝐶𝑛
24 [D]
Next list (SRTT sorted)
𝐴2
𝐶1
…
𝐶𝑘
𝐴2
V
SRTT Operations [I]nit
[U]date [D]ecay
[E]rror
Resolver’s SRTT Cache
The Attack
WHO
ibm.com zone
Attacker
Resolver
V NS
SRTT
OP
V
98000 [D]
NS
90000 [U]
𝐴2
9800 [D]
𝐴1
78443 [U]
𝐶1
22 [D]
𝐶2
84341 [U]
⋮
𝐴1
𝐶𝑘
31 [D]
⋮ 𝐶𝑛
24 [D]
Next list (SRTT sorted)
𝐴2
𝐶1
…
𝐶𝑘
𝐴2
V
SRTT Operations [I]nit
[U]date [D]ecay
[E]rror
Resolver’s SRTT Cache
The Attack
WHO
ibm.com zone
Attacker
Resolver
V NS
SRTT
OP
V
98000 [D]
NS
90000 [U]
𝐴2
9800 [D]
𝐴1
78443 [U]
𝐶1
22 [D]
𝐶2
84341 [U]
⋮
𝐴1
𝐶𝑘
31 [D]
⋮ 𝐶𝑛
24 [D]
Next list (SRTT sorted)
𝐴2
𝐶1
…
𝐶𝑘
𝐴2
V
SRTT Operations [I]nit
[U]date [D]ecay
[E]rror
Resolver’s SRTT Cache
The Attack
WHO
ibm.com zone
Attacker
Resolver
V NS
𝐶1 , What is the IP of attack.a1.foo?
𝐴1
SRTT
OP
V
98000 [D]
NS
90000 [U]
𝐴2
9800 [D]
𝐴1
78443 [U]
𝐶1
22 [D]
𝐶2
84341 [U]
⋮ 𝐶𝑘
31 [D]
⋮ 𝐶𝑛
24 [D]
Next list (SRTT sorted)
𝐴2
𝐶1
…
𝐶𝑘
𝐴2
V
SRTT Operations [I]nit
[U]date [D]ecay
[E]rror
Resolver’s SRTT Cache
The Attack
WHO
ibm.com zone
Attacker
Resolver
Query refused.
𝐴1
V NS
SRTT
OP
V
96040 [D]
NS
90000 [U]
𝐴2
9604 [D]
𝐴1
78443 [U]
𝐶1
63289 [U]
𝐶2
84341 [U]
⋮ 𝐶𝑘
30 [D]
⋮ 𝐶𝑛
23 [D]
Next list (SRTT sorted)
𝐴2
𝐶1
…
𝐶𝑘
𝐴2
V
SRTT Operations [I]nit
[U]date [D]ecay
[E]rror
Resolver’s SRTT Cache
The Attack
WHO
ibm.com zone
Attacker
Resolver
Query refused.
𝐴1
V NS
SRTT
OP
V
96040 [D]
NS
90000 [U]
𝐴2
9604 [D]
𝐴1
78443 [U]
𝐶1
63289 [U]
𝐶2
84341 [U]
⋮ 𝐶𝑘
30 [D]
⋮ 𝐶𝑛
23 [D]
Next list (SRTT sorted)
𝐴2
…
𝐶𝑘
𝐴2
V
SRTT Operations [I]nit
[U]date [D]ecay
[E]rror
After 𝑛 − 1 Iterations…
Resolver’s SRTT Cache
The Attack ibm.com zone
Attacker
Resolver
V NS
WHO
SRTT
OP
V
100000 ⋅ 0.98𝑛−1 [D]
NS
90000 [U]
𝐴2
10000 ⋅ 0.98𝑛−1 [D]
𝐴1
78443 [U]
𝐶1
63289 [U]
𝐶2
84341 [U]
⋮
𝐴1
32 ⋅ 0.98𝑛−1 [D]
𝐶𝑘 ⋮ 𝐶𝑛
53248 [U]
Next list (SRTT sorted)
𝐴2
𝐶𝑘
𝐴2
V
SRTT Operations [I]nit
[U]date [D]ecay
[E]rror
Resolver’s SRTT Cache
The Attack ibm.com zone
Attacker
Resolver
V NS
WHO
SRTT
OP
V
100000 ⋅ 0.98𝑛−1 [D]
NS
90000 [U]
𝐴2
10000 ⋅ 0.98𝑛−1 [D]
𝐴1
78443 [U]
𝐶1
63289 [U]
𝐶2
84341 [U]
⋮
𝐴1
32 ⋅ 0.98𝑛−1 [D]
𝐶𝑘 ⋮ 𝐶𝑛
53248 [U]
Next list (SRTT sorted)
𝐴2
𝐶𝑘
𝐴2
V
SRTT Operations [I]nit
[U]date [D]ecay
[E]rror
Resolver’s SRTT Cache
The Attack ibm.com zone
Attacker
Resolver
V NS
𝐶𝑘 , What is the IP of attack.a1.foo?
𝐴1
WHO
SRTT
OP
V
100000 ⋅ 0.98𝑛−1 [D]
NS
90000 [U]
𝐴2
10000 ⋅ 0.98𝑛−1 [D]
𝐴1
78443 [U]
𝐶1
63289 [U]
𝐶2
84341 [U]
⋮ 32 ⋅ 0.98𝑛−1 [D]
𝐶𝑘 ⋮ 𝐶𝑛
53248 [U]
Next list (SRTT sorted)
𝐴2
𝐶𝑘
𝐴2
V
SRTT Operations [I]nit
[U]date [D]ecay
[E]rror
Resolver’s SRTT Cache
The Attack
WHO
Attacker
Resolver
Query refused
𝐴1
V NS
OP
100000 ⋅ 0.98𝑛 [D]
V ibm.com zone
SRTT
NS
90000 [U]
𝐴2
10000 ⋅ 0.98𝑛 [D]
𝐴1
78443 [U]
𝐶1
63289 [U]
𝐶2
84341 [U]
⋮ 𝐶𝑘
91203 [U]
⋮ 𝐶𝑛
53248 [U]
Next list (SRTT sorted)
𝐴2
𝐶𝑘
𝐴2
V
SRTT Operations [I]nit
[U]date [D]ecay
[E]rror
Resolver’s SRTT Cache
The Attack
WHO
Attacker
Resolver
Query refused
𝐴1
V NS
OP
100000 ⋅ 0.98𝑛 [D]
V ibm.com zone
SRTT
NS
90000 [U]
𝐴2
10000 ⋅ 0.98𝑛 [D]
𝐴1
78443 [U]
𝐶1
63289 [U]
𝐶2
84341 [U]
⋮ 𝐶𝑘
91203 [U]
⋮ 𝐶𝑛
53248 [U]
Next list (SRTT sorted)
𝐴2
𝐶𝑘
𝐴2
V
SRTT Operations [I]nit
[U]date [D]ecay
[E]rror
Resolver’s SRTT Cache
The Attack
WHO
SRTT
100000 ⋅ 0.98𝑛 [D]
V ibm.com zone
Attacker
Resolver
Query refused
𝐴1
V NS
OP
NS
90000 [U]
𝐴2
10000 ⋅ 0.98𝑛 [D]
𝐴1
78443 [U]
𝐶1
63289 [U]
𝐶2
84341 [U]
⋮ 𝐶𝑘
91203 [U]
⋮ 𝐶𝑛
53248 [U]
Next list (SRTT sorted)
𝐴2
𝐴2
V
SRTT Operations [I]nit
[U]date [D]ecay
[E]rror
Resolver’s SRTT Cache
The Attack
WHO
SRTT
100000 ⋅ 0.98𝑛 [D]
V ibm.com zone
Attacker
Resolver
V NS
OP
NS
90000 [U]
𝐴2
10000 ⋅ 0.98𝑛 [D]
𝐴1
78443 [U]
𝐶1
63289 [U]
𝐶2
84341 [U]
⋮
𝐴1
𝐶𝑘
91203 [U]
⋮ 𝐶𝑛
53248 [U]
Next list (SRTT sorted)
𝐴2
𝐴2
V
SRTT Operations [I]nit
[U]date [D]ecay
[E]rror
Resolver’s SRTT Cache
The Attack
WHO
SRTT
100000 ⋅ 0.98𝑛 [D]
V ibm.com zone
Resolver
Attacker
V NS
OP
NS
90000 [U]
𝐴2
10000 ⋅ 0.98𝑛 [D]
𝐴1
78443 [U]
𝐶1
63289 [U]
𝐶2
84341 [U]
⋮
𝐴1
What is the IP of attack.a1.foo?
𝐶𝑘
91203 [U]
⋮ 𝐶𝑛
53248 [U]
Next list (SRTT sorted)
𝐴2
𝐴2
V
SRTT Operations [I]nit
[U]date [D]ecay
[E]rror
Resolver’s SRTT Cache
The Attack ibm.com zone
Resolver
Attacker
V NS
WHO
SRTT
OP
V
100000 ⋅ 0.98𝑛+1 [D]
NS
90000 [U]
𝐴2
12003 [U]
𝐴1
78443 [U]
𝐶1
63289 [U]
𝐶2
84341 [U]
⋮
𝐴1
attack.a1.foo’s IP is 6.6.6.6.
𝐶𝑘
91203 [U]
⋮ 𝐶𝑛
53248 [U]
Next list (SRTT sorted)
𝐴2
𝐴2
V
SRTT Operations [I]nit
[U]date [D]ecay
[E]rror
Resolver’s SRTT Cache
The Attack ibm.com zone
Attacker
attack.a1.foo’s IP is 6.6.6.6.
Resolver
V NS
WHO
SRTT
OP
V
100000 ⋅ 0.98𝑛+1 [D]
NS
90000 [U]
𝐴2
12003 [U]
𝐴1
78443 [U]
𝐶1
63289 [U]
𝐶2
84341 [U]
⋮
𝐴1
𝐶𝑘
91203 [U]
⋮ 𝐶𝑛
53248 [U]
Next list (SRTT sorted)
𝐴2 SRTT Operations [I]nit
[U]date [D]ecay
[E]rror
Resolver’s SRTT Cache
The Attack ibm.com zone
Attacker
𝐴1
V
Resolver large value of 𝑛, NS the attacked resolver times out (after 30 seconds), so we don’t even need 𝐴2 .
attack.a1.foo’s IP is For a sufficiently 6.6.6.6.
WHO
SRTT
OP
V
100000 ⋅ 0.98𝑛+1 [D]
NS
90000 [U]
𝐴2
12003 [U]
𝐴1
78443 [U]
𝐶1
63289 [U]
𝐶2
84341 [U]
⋮ 𝐶𝑘
91203 [U]
⋮ 𝐶𝑛
53248 [U]
Next list (SRTT sorted)
𝐴2 SRTT Operations [I]nit
[U]date [D]ecay
[E]rror
Wrap-up • We lowered the SRTT value of an arbitrary NS to an arbitrary value. • Cool features of the attack: • The attack is deterministic and requires 3 packets only. • We abuse non-open resolvers in contrast to many attacks that abuse open ones. • Recovery is not instant as of the SRTT update operation.
• The general lesson is to separate the cache. Never maintain a shared one.
Resolver’s SRTT Cache WHO
SRTT
OP
V
100000 ⋅ 0.98𝑛+1 [D]
NS
90000 [U]
𝐴2
12003 [U]
𝐴1
78443 [U]
𝐶1
63289 [U]
𝐶2
84341 [U]
⋮ 𝐶𝑘
91203 [U]
⋮ 𝐶𝑛
53248 [U]
Next list (SRTT sorted) V
NS
SRTT Operations [I]nit
[U]date [D]ecay
[E]rror
? Thank you.
