1 page.title=Security Enhancements in Android 1.5 through 4.1 2 @jd:body 3 4 <p> 5 Android provides a multi-layered security model described in the <a href="{@docRoot}security/index.html">Android 6 Security Overview</a>. Each update to Android includes dozens of 7 security enhancements to protect users. The following are some of the security 8 enhancements introduced in Android versions 1.5 through 4.1:</p> 9 10 <dl> 11 <dt><strong>Android 1.5</strong></dt> 12 <dd><ul> 13 <li>ProPolice to prevent stack buffer overruns (-fstack-protector)</li> 14 <li>safe_iop to reduce integer overflows</li> 15 <li>Extensions to OpenBSD dlmalloc to prevent double free() vulnerabilities and 16 to prevent chunk consolidation attacks. Chunk consolidation attacks are a 17 common way to exploit heap corruption.</li> 18 <li>OpenBSD calloc to prevent integer overflows during memory allocation</li> 19 </ul> 20 </dd> 21 22 <dt><strong>Android 2.3</strong></dt> 23 <dd><ul> 24 <li>Format string vulnerability protections (-Wformat-security -Werror=format-security)</li> 25 <li>Hardware-based No eXecute (NX) to prevent code execution on the stack and heap</li> 26 <li>Linux mmap_min_addr to mitigate null pointer dereference privilege 27 escalation (further enhanced in Android 4.1)</li> 28 </ul> 29 </dd> 30 31 <dt><strong>Android 4.0</strong></dt> 32 <dd>Address Space Layout Randomization (ASLR) to randomize key locations in memory 33 </dd> 34 35 <dt><strong>Android 4.1</strong></dt> 36 <dd><ul> 37 <li>PIE (Position Independent Executable) support</li> 38 <li>Read-only relocations / immediate binding (-Wl,-z,relro -Wl,-z,now)</li> 39 <li>dmesg_restrict enabled (avoid leaking kernel addresses)</li> 40 <li>kptr_restrict enabled (avoid leaking kernel addresses)</li> 41 </ul> 42 </dd> 43 44 </dl> 45
