EE579T/10 #1 Spring 2005 © , Richard A. Stanley EE579T Network Security 10: An Overview of SNMP Prof. Richard A. Stanley

EE579T/10 #2 Spring 2005 © , Richard A. Stanley Overview of Tonight’s Class Review last week’s lesson SNMP

EE579T/10 #3 Spring 2005 © , Richard A. Stanley Summary Computer crime is a fast-growing area of illegal activity “That’s where the money is” Computers and networks are regulated by a large and growing body of law Both civil and criminal issues involved Liability is a major consideration for any business or practitioner

EE579T/10 #4 Spring 2005 © , Richard A. Stanley Top Ten Security Concerns

EE579T/10 #5 Spring 2005 © , Richard A. Stanley SNMP Outline Basic Concepts of SNMP SNMPv1 Community Facility SNMPv2 SNMPv3

EE579T/10 #6 Spring 2005 © , Richard A. Stanley Why SNMP? To provide a simple means of managing objects across a network –These objects need not be network elements –The objects need not support SNMP (although it makes things easier if they do!) –“Management” can be tailored to mean what we need it to mean First introduced in 1988

EE579T/10 #7 Spring 2005 © , Richard A. Stanley Basic Concepts of SNMP An integrated collection of tools for network monitoring and control. –Single operator interface –Minimal amount of separate equipment. Software and network communications capability built into the existing equipment SNMP key elements: –Management station (physical device) –Management agent (software implementation) –Management information base (collection of objects) –Network Management protocol Get, Set and Trap

EE579T/10 #8 Spring 2005 © , Richard A. Stanley SNMP MIB Management Information Base = MIB –Database held at the managed client –Scalar variables –2D tables Uses streamlined protocol to: –Allow manager to Get and Set MIB variables –Enable agent to issue unsolicited notifications These are called traps

EE579T/10 #9 Spring 2005 © , Richard A. Stanley SNMP Characteristics Runs over UDP/IP or TCP/IP, depending on version Uses –Port 161 (for messages) –Port 162 (for traps)

EE579T/10 #10 Spring 2005 © , Richard A. Stanley SNMP Protocol

EE579T/10 #11 Spring 2005 © , Richard A. Stanley SNMP Commands Get –Query a MIB for information Set –Set values in a MIB Trap –Send condition information –Asynchronous

EE579T/10 #12 Spring 2005 © , Richard A. Stanley SNMP Proxies SNMPv1 supports UDP over IP –Period! There are lots of clients out there that need to be managed and that don’t speak UDP Proxies bridge the gap –Provide translation of client management language to SNMP –Interfaces to SNMP for the client

EE579T/10 #13 Spring 2005 © , Richard A. Stanley Proxy Configuration

EE579T/10 #14 Spring 2005 © , Richard A. Stanley SNMPv2 Allows use of TCP/IP, and others Provides additional management features –Distributed network management Single-server hierarchical networks get overloaded –Functional enhancements GetBulk – retrieve block of data at once Inform – intra-management station communications of events and/or conditions Removes atomicity from the Get command

EE579T/10 #15 Spring 2005 © , Richard A. Stanley SNMP v1 and v2 SNMPv2 intended deal with deficiencies of SNMPv1 –Introduced first in 1993 SNMPv1 is “connectionless” –Just like HTTP –Why? Utilizes UDP as the transport layer protocol. SNMPv2 allows use of TCP for “reliable, connection-oriented” service

EE579T/10 #16 Spring 2005 © , Richard A. Stanley SNMPv2 Distributed Management

EE579T/10 #17 Spring 2005 © , Richard A. Stanley SNMPv1 vs. SNMPv2 SNMPv1SNMPv2 Direction Description GetRequest Manager to agentRequest value for each listed object GetNext Manager to agentRequest next value for each listed object GetBulkRequestManager to agentRequest multiple values SetRequest Manager to agentSet value for each listed object InformRequestManager to managerTransmit unsolicited information GetResponseResponseAgent to manager or Manage to manager(SNMPv2) Respond to manager request TrapSNMPv2-TrapAgent to managerTransmit unsolicited information

EE579T/10 #18 Spring 2005 © , Richard A. Stanley SNMPv1 Community Facility SNMP Community – Relationship between an SNMP agent and SNMP managers –Think of a network domain as an analog Three aspects of agent control: –Authentication service –Access policy –Proxy service

EE579T/10 #19 Spring 2005 © , Richard A. Stanley SNMPv1 Administrative Concepts

EE579T/10 #20 Spring 2005 © , Richard A. Stanley Access Policy SNMP MIB View –Subset of objects within the MIB –May be on different MIB sub-trees SNMP Access Mode –Element of the set of MIB objects –Defined for each community These two together are the SNMP Community Profile

EE579T/10 #21 Spring 2005 © , Richard A. Stanley What About Proxied Clients? Supported within community concept Proxy is an SNMP agent that acts on behalf of other (foreign) devices –For each device supported, SNMP proxy maintains an access policy –Therefore, proxy knows which MIB objects can be used to manage the proxied system, and their access mode

EE579T/10 #22 Spring 2005 © , Richard A. Stanley Where is the Security? SNMPv1 has no inherent security –Messages can be spoofed, altered, or deleted –Does this have a potential for evil? SNMPv2 doesn’t have any, either –It actually makes things worse by introducing the distributed management concept What to do?

EE579T/10 #23 Spring 2005 © , Richard A. Stanley Enter SNMPv3 Framework for incorporating security into SNMPv1 or SNMPv2 –Introduced 1998 Not a standalone replacement for either v1 or v2 !! –Adds security to v1 or v2 –Requires underlying SNMP system Not yet completely standardized

EE579T/10 #24 Spring 2005 © , Richard A. Stanley SNMPv3 Architecture

EE579T/10 #25 Spring 2005 © , Richard A. Stanley Traditional SNMP Manager

EE579T/10 #26 Spring 2005 © , Richard A. Stanley Traditional SNMP Agent

EE579T/10 #27 Spring 2005 © , Richard A. Stanley SNMPv3 Message Flow

EE579T/10 #28 Spring 2005 © , Richard A. Stanley SNMP3 Message Format with USM

EE579T/10 #29 Spring 2005 © , Richard A. Stanley User Security Model (USM) Designed to secure against: –Modification of information (integrity) –Masquerade (authentication) –Message stream modification (stream integrity) –Disclosure (confidentiality) Not intended to secure against: –Denial of Service (DoS attack) –Traffic analysis

EE579T/10 #30 Spring 2005 © , Richard A. Stanley In Theory (according to the standards folks)… DoS attacks may look like network failure (imagine that!) DoS should be dealt with by an overall network security capability, not one embedded in a protocol Traffic analysis no problem, as management traffic highly predictable anyway What do you think?

EE579T/10 #31 Spring 2005 © , Richard A. Stanley USM Encryption Authentication (using authKey) –HMAC-MD5-96 –HMAC-SHA1-96 Encryption (using privKey) –DES CBC –Uses first 64 bits of the 16-octet privKey –Last 64 bits used as IV to DES CBC Key values not accessible from SNMP

EE579T/10 #32 Spring 2005 © , Richard A. Stanley Authoritative Engine SNMP messages with payloads that expect a response (Get…, Set, Inform) –Receiver of message is authoritative SNMP messages with payload that does not expect response (Trap, Response, Report) –Sender is authoritative So what?

EE579T/10 #33 Spring 2005 © , Richard A. Stanley Key Localization Allows single user to own keys stored in multiple engines –Key localized to each authoritative engine using hash functions –Avoids problem of a single key being stored in many places Greatly slows brute force attack

EE579T/10 #34 Spring 2005 © , Richard A. Stanley Key Localization Process

EE579T/10 #35 Spring 2005 © , Richard A. Stanley Timeliness Determined by a clock kept at the authoritative engine –When authoritative engine sends a message, it includes the current clock value Nonauthoritative agent synchronizes on clock value –When nonauthoritative engine sends a message, it includes the estimated destination clock value These procedures allow assessing message timeliness Why do we care?

EE579T/10 #36 Spring 2005 © , Richard A. Stanley View-Based Access Control Model (VACM) VACM has two characteristics: –Determines whether access to a managed object should be allowed. –Make use of an MIB that: Defines the access control policy for this agent. Makes it possible for remote configuration to be used.

EE579T/10 #37 Spring 2005 © , Richard A. Stanley Access Control Logic in VACM

EE579T/10 #38 Spring 2005 © , Richard A. Stanley SNMPv3 Security SNMPv3 solves SNMP security problems, right? –NOT! Decent security implementation, but reality is: –SNMPv1 still holds ~95% of the market –Even SNMPv2 not widely deployed –Upgrading to SNMPv3 is difficult and costly (sort of like moving from Win95 to WinXP all at once) –There is the issue of proxies and foreign clients SNMPv3 is the clear long-term choice

EE579T/10 #39 Spring 2005 © , Richard A. Stanley Recent SNMP Security Events CERT Advisory 12 Feb 02, Revised 26 Mar 02, warns about potential for –unauthorized privileged access (which allows, inter alia, enumeration of SNMP agents) –denial of service attacks –unstable behavior Vulnerabilities in both messages and traps Vulnerabilities are in SNMPv1!

EE579T/10 #40 Spring 2005 © , Richard A. Stanley This is Not New News! After this class, are you surprised? These vulnerabilities have been in SNMP since Day One Only now, with an increased emphasis on security, are they getting the attention they deserve Officially, the vulnerabilities have not been exploited. Unofficially, they have.

EE579T/10 #41 Spring 2005 © , Richard A. Stanley Summary SNMP is widely-used for managing clients distributed across a network SNMPv1 is simple, effective, and provides the majority of SNMP service in the field SNMPv2 adds some functionality to v1 SNMPv3 is a security overlay for either version, not a standalone replacement SNMP security is a major issue!

EE579T/10 #42 Spring 2005 © , Richard A. Stanley Homework Read Stallings, Chapter 8 Do Problems 8.2, 8.4, 8.8