Messages in this thread | | | Date | Fri, 2 Jul 2010 21:35:50 +0200 | Subject | procfs gives read/write access to RO/WO pipes | From | Frank Heckenbach <> |
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Using /proc/*/fd, you can get read/write access to a pipe that you have read-only or write-only access to. The program below demonstrates this. It reads and writes through the "0" fd. Tested with 2.6.34, i686.
At first sight, it doesn't look too serious if a program can write to its own readable pipe, or read from its writeable pipe, but perhaps I'm just not creative enough to see an exploit. Also, I don't know it it might affect other file types where it might be a real problem. At least, it does seem to violate the permissions.
#include <unistd.h> #include <stdio.h> #include <fcntl.h>
int main () { char a, n[64]; int p[2], f, r; pipe (p); sprintf (n, "/proc/self/fd/%i", p[0]); f = open (n, O_RDWR); write (f, "x", 1); r = read (f, &a, 1); fprintf (stderr, "%i %c\n", r, a); return 0; }
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