Computer system having memory protection function
A computer system and storage protection technology, applied in the direction of memory system, computing, preventing unauthorized use of memory, etc., to achieve the effect of preventing buffer overflow attacks
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no. 1 approach
[0065] FIG. 1 shows a schematic configuration example of a system 1 of the present invention. As shown in Figure 1, system 1 of the present invention is constituted as, has: CPU (central processing unit) 10, ROM (read-only memory) 11, RAM 12, nonvolatile memory 13, peripheral I / O connect 14, memory map circuit 15 , access right judging circuit 16 , data bus 17 , and address bus 18 . CPU 10 , ROM 11 , RAM 12 , nonvolatile memory 13 , and peripheral I / O interface 14 are connected to each other through address bus 18 and data bus 17 . The ROM 11 , the RAM 12 , and the nonvolatile memory 13 constitute a storage area 19 for storing program codes executable by the CPU 10 and for storing data.
[0066] Furthermore, in the present embodiment, among the storage areas 19, a program code area storing program codes and a fixed data area storing fixed data are formed in the ROM 11 and the nonvolatile memory 13, and are utilized when the program is executed. Assuming that the storage area...
Embodiment 1
[0072] Next, an example of the defense operation of the system 1 of the present invention when receiving a buffer overflow attack as illustrated in FIG. 5 will be described. FIG. 7 shows execution of a normal program, prevention of execution of a malicious illegal program, and status changes of the stack area when a buffer overflow attack is received (#13 to #15).
[0073] #13: Operation when buffer overflow attack is received The same operation as #6 to #8 shown in FIG. 5 is performed.
[0074]#14: Based on the falsified return address, the CPU 10 transfers control to a malicious illegal program embedded in a stack area set within an execution-unpermitted address range. Here, the access right judging circuit 16 detects that the execution program storage address Spc indicated by the value of the program counter 20 is within the execution disallowed address range of the access control memory map stored in the memory mapping circuit 15, and activates access prohibition. Signal ...
Embodiment 2
[0080] Next, another example of the defense operation of the system 1 of the present invention when receiving a buffer overflow attack as illustrated in FIG. 5 will be described. In this second embodiment, the operation of defending against a buffer overflow attack will be described with the entire system as an initial state.
[0081] FIG. 8 shows the execution of the program when the execution of the malicious illegal program is detected and the reset process is performed, the execution of the malicious illegal program is prevented, and the state changes of the stack area (#16 to #18).
[0082] #16: Operation when buffer overflow attack is received The same operation as #6 to #8 shown in FIG. 5 is performed.
[0083] #17: Based on the falsified return address, the CPU 10 transfers control to a malicious illegal program embedded in a stack area set within an execution-unpermitted address range. Here, the access right judging circuit 16 detects that the execution program stora...
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