commit 4702cdc99d734ebb7bbb68d65c00a91fdbc13463 Author: Cristian Toader <cristian.matei.toader@gmail.com> Date: Thu Sep 12 13:43:06 2013 +0300 added extra buffer and limit to mprotect not to exceed the length of that buffer --- src/common/sandbox.c | 31 ++++++++++++++++++++++++------- 1 file changed, 24 insertions(+), 7 deletions(-) diff --git a/src/common/sandbox.c b/src/common/sandbox.c index 6d1e6ef..5961c06 100644 --- a/src/common/sandbox.c +++ b/src/common/sandbox.c @@ -15,6 +15,9 @@ */ #define _LARGEFILE64_SOURCE +/** Malloc mprotect limit in bytes. */ +#define MALLOC_MP_LIM 1048576 + #include <stdio.h> #include <string.h> #include <stdlib.h> @@ -50,6 +53,10 @@ #include <time.h> #include <poll.h> +// TODO: remove test +static void *test_buf_base = NULL; +static int test_buf_len = 0; + /**Determines if at least one sandbox is active.*/ static int sandbox_active = 0; /** Holds the parameter list configuration for the sandbox.*/ @@ -817,9 +824,9 @@ prot_strings(scmp_filter_ctx ctx, sandbox_cfg_t* cfg) pr_mem_size += strlen((char*) ((smp_param_t*)el->param)->value) + 1; } - // allocate protected memory - pr_mem_base = (char*) mmap(NULL, pr_mem_size, PROT_READ | PROT_WRITE, - MAP_PRIVATE | MAP_ANON, -1, 0); + // allocate protected memory with MALLOC_MP_LIM canary + pr_mem_base = (char*) mmap(NULL, MALLOC_MP_LIM + pr_mem_size, + PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0); if (pr_mem_base == MAP_FAILED) { log_err(LD_BUG,"(Sandbox) failed allocate protected memory! mmap: %s", strerror(errno)); @@ -827,7 +834,7 @@ prot_strings(scmp_filter_ctx ctx, sandbox_cfg_t* cfg) goto out; } - pr_mem_next = pr_mem_base; + pr_mem_next = pr_mem_base + MALLOC_MP_LIM; pr_mem_left = pr_mem_size; // change el value pointer to protected @@ -857,8 +864,12 @@ prot_strings(scmp_filter_ctx ctx, sandbox_cfg_t* cfg) } } + // TODO: remove, test + test_buf_base = pr_mem_base; + test_buf_len = pr_mem_size; + // protecting from writes - if (mprotect(pr_mem_base, pr_mem_size, PROT_READ)) { + if (mprotect(pr_mem_base, MALLOC_MP_LIM + pr_mem_size, PROT_READ)) { log_err(LD_BUG,"(Sandbox) failed to protect memory! mprotect: %s", strerror(errno)); ret = -3; @@ -890,9 +901,13 @@ prot_strings(scmp_filter_ctx ctx, sandbox_cfg_t* cfg) * * PROT_READ|PROT_WRITE was originally fully allowed in sb_mprotect(), but * had to be removed due to limitation of libseccomp regarding intervals. + * + * There is a restriction on how much you can mprotect with R|W up to the + * size of the canary. */ ret = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(mprotect), 2, SCMP_CMP(0, SCMP_CMP_LT, (intptr_t) pr_mem_base), + SCMP_CMP(1, SCMP_CMP_LE, MALLOC_MP_LIM), SCMP_CMP(2, SCMP_CMP_EQ, PROT_READ|PROT_WRITE)); if (ret) { log_err(LD_BUG,"(Sandbox) mprotect protected memory filter fail (LT)!"); @@ -900,8 +915,10 @@ prot_strings(scmp_filter_ctx ctx, sandbox_cfg_t* cfg) } ret = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(mprotect), 2, - SCMP_CMP(0, SCMP_CMP_GT, (intptr_t) pr_mem_base + pr_mem_size), - SCMP_CMP(2, SCMP_CMP_EQ, PROT_READ|PROT_WRITE)); + SCMP_CMP(0, SCMP_CMP_GT, (intptr_t) pr_mem_base + pr_mem_size + + MALLOC_MP_LIM), + SCMP_CMP(1, SCMP_CMP_LE, MALLOC_MP_LIM), + SCMP_CMP(2, SCMP_CMP_EQ, PROT_READ|PROT_WRITE)); if (ret) { log_err(LD_BUG,"(Sandbox) mprotect protected memory filter fail (GT)!"); return ret;