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Use LD_PRELOAD to inject pledge() in glibc progs

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We're now able to drop both `exec` and `prot_exec` privileges
automatically when launching glibc dynamic executables. We also have
really outstanding standard error logging now, that explains which
promises are needed, even in cases where `exec` is used.
This commit is contained in:
Justine Tunney 2022-08-08 21:23:37 -07:00
parent 0277d7d6e9
commit 6b3d257588
5 changed files with 286 additions and 178 deletions
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50
tool/build/dso/sandbox.c Normal file
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/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2022 Justine Alexandra Roberts Tunney │
│ │
│ Permission to use, copy, modify, and/or distribute this software for │
│ any purpose with or without fee is hereby granted, provided that the │
│ above copyright notice and this permission notice appear in all copies. │
│ │
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
│ PERFORMANCE OF THIS SOFTWARE. │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/calls/calls.h"
#include "libc/calls/pledge.h"
#include "libc/calls/pledge.internal.h"
#include "libc/intrin/promises.internal.h"
#include "libc/runtime/runtime.h"
/*
* runs pledge at glibc executable load time, e.g.
* strace -vff bash -c '_PLEDGE=4194303,0,1 LD_PRELOAD=$HOME/sandbox.so ls'
*/
hidden uint8_t __privileged_start[1];
hidden uint8_t __privileged_end[1];
__attribute__((__constructor__)) void init(void) {
int c, i, j;
const char *s;
uint64_t arg[3] = {0};
s = getenv("_PLEDGE");
for (i = j = 0; i < 3; ++i) {
while ((c = s[j] & 255)) {
++j;
if ('0' <= c & c <= '9') {
arg[i] *= 10;
arg[i] += c - '0';
} else {
break;
}
}
}
sys_pledge_linux(~arg[0], arg[1], arg[2]);
}