62 lines
1.4 KiB
C
62 lines
1.4 KiB
C
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#include <unistd.h>
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#include <fcntl.h>
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#include <sys/wait.h>
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#include "syscall.h"
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#include "pthread_impl.h"
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struct ctx {
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int fd;
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const char *filename;
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int amode;
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int p;
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};
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static int checker(void *p)
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{
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struct ctx *c = p;
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int ret;
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if (__syscall(SYS_setregid, __syscall(SYS_getegid), -1)
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|| __syscall(SYS_setreuid, __syscall(SYS_geteuid), -1))
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__syscall(SYS_exit, 1);
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ret = __syscall(SYS_faccessat, c->fd, c->filename, c->amode, 0);
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__syscall(SYS_write, c->p, &ret, sizeof ret);
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return 0;
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}
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int faccessat(int fd, const char *filename, int amode, int flag)
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{
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if (flag) {
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int ret = __syscall(SYS_faccessat2, fd, filename, amode, flag);
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if (ret != -ENOSYS) return __syscall_ret(ret);
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}
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if (flag & ~AT_EACCESS)
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return __syscall_ret(-EINVAL);
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if (!flag || (getuid()==geteuid() && getgid()==getegid()))
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return syscall(SYS_faccessat, fd, filename, amode);
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char stack[1024];
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sigset_t set;
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pid_t pid;
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int status;
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int ret, p[2];
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if (pipe2(p, O_CLOEXEC)) return __syscall_ret(-EBUSY);
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struct ctx c = { .fd = fd, .filename = filename, .amode = amode, .p = p[1] };
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__block_all_sigs(&set);
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pid = __clone(checker, stack+sizeof stack, 0, &c);
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__syscall(SYS_close, p[1]);
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if (pid<0 || __syscall(SYS_read, p[0], &ret, sizeof ret) != sizeof(ret))
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ret = -EBUSY;
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__syscall(SYS_close, p[0]);
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__syscall(SYS_wait4, pid, &status, __WCLONE, 0);
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__restore_sigs(&set);
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return __syscall_ret(ret);
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}
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