Security in Application SDLC Barkan Asaf abarkan mercury

Security in Application & SDLC Barkan Asaf (abarkan@mercury. com) Nov, 2006 1

Application Load Balancer Application Client App Server Hardened OS DMZ Firewall External Network Databases Web Server Proxy Firewall Network Layer Application Layer Security Perimeter Internal Segment 2

Web Application attacks & 5 Web Security Myths Top Five myths of web security • We use 128 -Bit SSL • Firewalls protect the web site • My network scanner found no issues • My application scanner found no issues • We have annual security assessments Jeremiah Grossman 3

Vulnerability Stack & Security scanners 4

Technical vs. Logical Vulnerabilities Logical Flaws Security vulnerabilities that arise with some contextual logic in application. Example: • Multi step procedure that can be bypassed with direct invocation Technical Vulnerability Security vulnerabilities that can be discovered without any contextual logic Examples: • HTML Injection • SQL Injection Web Application scanners limitations/challenges • Session state management • • • Script parsing Logical flows Custom URLs Privilege escalation False negative/positive Technical vs. Logical Vulnerabilities at White. Hat 5

Security Tollgates in Software Development Life Cycle (SDLC) Release Cycle Product Requirements Functional Design Technical Design Implementation Testing Beta Security Tollgates Security Requirements Document Architectural Risk Analysis Secure Coding Security Testing 6

Unvalidated Input (A 1) Description HTTP inputs into the application are not validated. Include URL, Headers, query strings, cookies, form fields, hidden fields. Leads to almost all web application vulnerabilities. Threats Client-side Attacks (3), Command Execution (4), Denial of Service (6. 2) Demonstration Counter measures Use Application level validation that includes: • Strong data type • Length • Logical Boundaries • Legal characters • Correct Syntax 7

Broken Access Control (A 2) Description Authorization boundaries in code are broken or not properly enforced. Threats Credential/Session prediction (2. 1), Insufficient Authorization (2. 3) Insufficient process validation (6. 4) Counter measures • Robust authorization management • Do not trust client side tokens for authorization • Authorize all requests except anonymous objects • Block resource enumeration and Forced Browsing in application 8

Broken Authentication & Session Management (A 3) Description A weak implementation of Authentication framework or unsecure Session management. Threats Brute Force (1. 1), Insufficient Authentication (1. 2), Insufficient session expiration (2. 3), Session fixation session (2. 4), Session prediction (2. 1) Demonstration Counter measures • Use Random GUID as session indication • Assign session id only after authentication • Assign new session id when change from HTTP<->HTTPS • Correlate session indication with valid session object in application • Use standard and robust Password policy enforcement • Use standard and robust Lockout policy enforcement • Do not trust client to send session state (session GUID only) 9

Cross Site Scripting (A 4) Description Attacker is using a vulnerable web application into sending unintentionally a user (Victim) a malicious active script that will be executed on its browser and breach his security framework. Threats Client-side attacks (3) Demonstration Counter measures • Use Application level validation that will either negatively or positively validate all inputs coming from untrusted clients. • Use HTML encoding centrally in presentation layer 10

Buffer Overflows (A 5) Description The attacker sends data to a program, which it stores in an undersized stack buffer. The result is that a either corrupted or malicious code is executed. Buffer overflow vulnerabilities typically occur in code that: • Relies on external data to control its behavior • Depends upon external properties of the data • Is so complex that a programmer cannot accurately predict its behavior Threats Buffer overflow (4. 1) Code Example char buf[BUFSIZE]; gets(buf); Counter measures • Use interpreted languages as Java/Python • Validate your input boundaries and size before processing 11

Injection Flaws (A 6) Description Attacker is using Injection flaws to relay malicious code through a web application to another System. The code is executed on behalf of the web application. Threats Command execution (4), Denial of Service (6. 2) Example Counter measures • Use Application level validation that will either negatively or positively validate all inputs coming from untrusted clients. • Use prepared statements and set each parameter before use in query 12

Improper Error Handling (A 7) Description Improper handling of errors in application can result with the application sending the attacker Error messages that reveal implementation/architecture/components information he should not know. Threats Information leakage (5. 2) Example • throw SQL exceptions back to client • throw stack trace on Web service exceptions • throw Application server stack trace back to client Counter measures • Catch all exceptions in server side – never throw exception to client • Handle all errors in back end • Do not send the user excessive information that is not required as Platform architecture ports in use , components in use and more. 13

Insecure Storage (A 8) Description Improper usage/implementation of cryptographic in code application. Examples Saving private key of SSL server on File system as clear text Saving DB connection object as clear text on file system Failure to encrypt critical data Poor sources of randomness Poor choice of algorithm Attempting to invent a new encryption algorithm Failure to include support for encryption key changes Threats Information leakage (5. 2), Insufficient Authentication (1. 2) Counter measures • Use well known and proven cryptographic • Choose a suited algorithm according to security/performance trade-off • Make secrets in memory not serialized • Make keys replaceable and configurable by size if possible • Encrypt all private/confidential credentials 14

Denial Of Service (A 9) Description All actions or procedures in application that will make it unusable. Network level attacks are not Included in here. Threats Denial of Service (6. 2) Example • Resource starvation when all concurrent users are used by zombies • HTML persistence injection causes Do. S to the application main page Counter measures • Use well known and proven cryptographic • Choose a suited algorithm according to security/performance trade-off • Make secrets in memory not serialized • Make keys replaceable and configurable by size if possible • Encrypt all private/confidential credentials 15

Insecure Configuration Management (A 10) Description Insecure usage of servers/components configuration. Mostly out of the box settings are not secure. Examples • Unpatched security flaws in the server software • Web server Misconfigurations (directory listing/traversal enabled) • Unnecessary default, backup, or sample files • Improper file and directory permissions • Unnecessary services enabled • Default accounts with their default passwords • Administrative or debugging functions that are enabled or accessible • Overly informative error messages (more details in the error handling section) • Unsecre usage of certificates Threats Insufficient Authentication (1. 2), Insufficient authorization (2. 2), SSI Injection (4. 6), Directory indexing (5. 1), Information leakage (5. 2), Path traversal (5. 3), Predictable Recourse Location (5. 4), Abuse of Functionality (6. 1) Counter measures • make hardening procedure to infrastructure before shipping 16

Summary • Loose the naïve approach regard client’s behavior * • Validate all inputs from untrusted clients * • No Such thing as Security in client side • Use standard security solutions/configuration • Make sure the client gets only the responses he needs * • Remove legacy/unnecessary resources from production app 17

Cross Site Scripting (XSS) The script, sent by the attacked client to the server was then received again by the client, now with the proper security context, and was able to send the cookie to the attacker 18

SQL Injection – Code example By passing Login logic using SQL Injection flaw SQLQuery = "SELECT Username FROM Users WHERE Username = ‘" & str. Username & "‘ AND Password = ‘" & str. Password & "‘" str. Auth. Check = Get. Query. Result(SQLQuery) If str. Auth. Check = "" bool. Authenticated = False Else bool. Authenticated = True End If Defending (Java example) Prepared. Statement ps = null; Record. Set rs = null; try { is. Safe(p. Username); ps = conn. prepare. Statement(“SELECT * FROM user_table WHERE username =‘? ’”); ps. set. String(1, p. Username); rs = ps. execute(); if ( rs. next() ) { … } 19

Validation layers (Secure in depth) 20