Writable XOR executable （W⊕X） and address space layout randomisation （ASLR） have elevated the understanding necessary to perpetrate buffer overflow exploits [1] . However, they have not proved to be a panacea [1 ...Writable XOR executable （W⊕X） and address space layout randomisation （ASLR） have elevated the understanding necessary to perpetrate buffer overflow exploits [1] . However, they have not proved to be a panacea [1 3] , and so other mechanisms, such as stack guards and prelinking, have been introduced. In this paper, we show that host-based protection still does not offer a complete solution. To demonstrate the protection inadequacies, we perform an over the network brute force return-to-libc attack against a preforking concurrent server to gain remote access to a shell. The attack defeats host protection including W⊕X and ASLR. We then demonstrate that deploying a network intrusion detection systems （NIDS） with appropriate signatures can detect this attack efficiently.展开更多
This paper investigates the electronic structure and thermodynamic properties of LiBC in the hexagonal structure by using the generalized gradient approximation （GGA） and local density approximation correction schem...This paper investigates the electronic structure and thermodynamic properties of LiBC in the hexagonal structure by using the generalized gradient approximation （GGA） and local density approximation correction scheme in the frame of density functional theory. The geometric structure of LiBC under zero pressure, and the dependences of the normalized lattice parameters a/ao and c/co, the ratio e/a, the normalized primitive volume V/Vo on pressure are given. The thermodynamic quantity （including the heat capacity Cv, Debye temperature 6~D, thermal expansion a and Grfineisen parameter -y） dependences on temperature and pressure are obtained through the GGA method and the quasi-harmonic Debye model. The band structures and density of state of LiBC under different pressures have also been analysed.展开更多
The thermodynamic properties of LiBC are investigated by using the full-potential linearlzed muffin-tin orbital method （FP-LMTO） within the frame of density functional theory （DFT） and using the quasi-harmonic Deb...The thermodynamic properties of LiBC are investigated by using the full-potential linearlzed muffin-tin orbital method （FP-LMTO） within the frame of density functional theory （DFT） and using the quasi-harmonic Debye model. The dependencies of the normalized lattice parameters a/a0 and c/c0, the ratio （c/a）/2, the normalized primitive volume V/V0 on pressure and temperature are successfully obtained. It is found that the interlayer covalent interactions （Li-B bonds or Li-C bonds） are more sensitive to temperature and pressure than intralayer ones （B-C bonds）, as gives rise to the extreme lattice anisotropy in the bulk hop LiBC.展开更多
当前大多数Linux发行版使用功能强大的glibc(GNU C library)作为C标准库(简称C库),但glibc的LGPL协议存在商用不友好条款,制约了商业Linux发行版的推广.一种可行的解决方案是选择某个与glibc相比尚有功能缺陷但适宜商用的C库加以补全,...当前大多数Linux发行版使用功能强大的glibc(GNU C library)作为C标准库(简称C库),但glibc的LGPL协议存在商用不友好条款,制约了商业Linux发行版的推广.一种可行的解决方案是选择某个与glibc相比尚有功能缺陷但适宜商用的C库加以补全,从而制成新的C库以替代glibc.开源欧拉(openEuler)操作系统社区以MIT协议的musl libc作为新的C库选型.新C库对已有应用软件的兼容是成功替换的关键,而精确的兼容性分析算法不仅可以定位缺失API,还可以量化计算兼容性和API补全的优先级.为此,提出兼容性分析算法来研究openEuler的4种主要软件生态中的musl libc兼容性和缺失API优先级.基于应用软件包之间的依赖关系和谷歌PageRank算法的思想,提出了PackageRank算法和APIRank算法,分别用于软件包兼容性度量和优先级计算.这2种算法提供了系统个性化兼容分析的方法,所需信息易于获取,适用于缺乏用户数据统计的、尚不完整而仍有开发需求的系统及构件.这2种算法在musl libc上的分析结果清晰准确,与软件生态的特点和现状相符,与musl libc的国际社区开发者的观点接近,为openEuler的新C库补全工作提供了有效指导.展开更多
基金supported by National Natural Science Foundation of China (No. 60873208)
文摘Writable XOR executable （W⊕X） and address space layout randomisation （ASLR） have elevated the understanding necessary to perpetrate buffer overflow exploits [1] . However, they have not proved to be a panacea [1 3] , and so other mechanisms, such as stack guards and prelinking, have been introduced. In this paper, we show that host-based protection still does not offer a complete solution. To demonstrate the protection inadequacies, we perform an over the network brute force return-to-libc attack against a preforking concurrent server to gain remote access to a shell. The attack defeats host protection including W⊕X and ASLR. We then demonstrate that deploying a network intrusion detection systems （NIDS） with appropriate signatures can detect this attack efficiently.
基金supported by the National Natural Science Foundation of China (Grant Nos 10776022 and 10576020)
文摘This paper investigates the electronic structure and thermodynamic properties of LiBC in the hexagonal structure by using the generalized gradient approximation （GGA） and local density approximation correction scheme in the frame of density functional theory. The geometric structure of LiBC under zero pressure, and the dependences of the normalized lattice parameters a/ao and c/co, the ratio e/a, the normalized primitive volume V/Vo on pressure are given. The thermodynamic quantity （including the heat capacity Cv, Debye temperature 6~D, thermal expansion a and Grfineisen parameter -y） dependences on temperature and pressure are obtained through the GGA method and the quasi-harmonic Debye model. The band structures and density of state of LiBC under different pressures have also been analysed.
基金The project supported by National Natural Science Foundation of China under Grant No. 10576020
文摘The thermodynamic properties of LiBC are investigated by using the full-potential linearlzed muffin-tin orbital method （FP-LMTO） within the frame of density functional theory （DFT） and using the quasi-harmonic Debye model. The dependencies of the normalized lattice parameters a/a0 and c/c0, the ratio （c/a）/2, the normalized primitive volume V/V0 on pressure and temperature are successfully obtained. It is found that the interlayer covalent interactions （Li-B bonds or Li-C bonds） are more sensitive to temperature and pressure than intralayer ones （B-C bonds）, as gives rise to the extreme lattice anisotropy in the bulk hop LiBC.
