commit 3d1f9f583a45143c1259b8926f8c57fa57fc1efb Author: Nick Mathewson nickm@torproject.org Date: Tue Jul 23 10:41:57 2019 -0400

Use special magic to enforce manager/object connection.

Every time we finalize a config manager, we now generate a new magic number for it, so that we'll get an assertion failure if we ever try to use an object with a different configuration manager than the one that generated it. --- src/app/config/confparse.c | 21 +++++++++++++++++++-- src/test/test_confparse.c | 1 - 2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/src/app/config/confparse.c b/src/app/config/confparse.c index c7ee8f301..998c0e6ef 100644 --- a/src/app/config/confparse.c +++ b/src/app/config/confparse.c @@ -37,6 +37,8 @@ #include "lib/string/printf.h" #include "lib/string/util_string.h"

+#include "ext/siphash.h" + /** * A managed_var_t is an internal wrapper around a config_var_t in * a config_format_t structure. It is used by config_mgr_t to @@ -89,6 +91,12 @@ struct config_mgr_t { * added to it. A manager must be frozen before it can be used to construct * or manipulate objects. */ bool frozen; + /** A replacement for the magic number of the toplevel object. We override + * that number to make it unique for this particular config_mgr_t, so that + * an object constructed with one mgr can't be used with another, even if + * those managers' contents are equal. + */ + struct_magic_decl_t toplevel_magic; };

#define IDX_TOPLEVEL (-1) @@ -186,7 +194,16 @@ managed_var_cmp(const void **a, const void **b) void config_mgr_freeze(config_mgr_t *mgr) { + static uint64_t mgr_count = 0; + smartlist_sort(mgr->all_vars, managed_var_cmp); + memcpy(&mgr->toplevel_magic, &mgr->toplevel->magic, + sizeof(struct_magic_decl_t)); + uint64_t magic_input[3] = { mgr->toplevel_magic.magic_val, + (uint64_t) (uintptr_t) mgr, + ++mgr_count }; + mgr->toplevel_magic.magic_val = + (uint32_t)siphash24g(magic_input, sizeof(magic_input)); mgr->frozen = true; }

@@ -238,7 +255,7 @@ config_mgr_assert_magic_ok(const config_mgr_t *mgr, tor_assert(mgr); tor_assert(options); tor_assert(mgr->frozen); - struct_check_magic(options, &mgr->toplevel->magic); + struct_check_magic(options, &mgr->toplevel_magic); }

/** Macro: assert that <b>cfg</b> has the right magic field for @@ -254,7 +271,7 @@ config_new(const config_mgr_t *mgr) tor_assert(mgr->frozen); const config_format_t *fmt = mgr->toplevel; void *opts = tor_malloc_zero(fmt->size); - struct_set_magic(opts, &fmt->magic); + struct_set_magic(opts, &mgr->toplevel_magic); CONFIG_CHECK(mgr, opts); return opts; } diff --git a/src/test/test_confparse.c b/src/test/test_confparse.c index 1513c9323..78eb3d38b 100644 --- a/src/test/test_confparse.c +++ b/src/test/test_confparse.c @@ -158,7 +158,6 @@ test_confparse_init(void *arg) config_init(mgr, tst);

// Make sure that options are initialized right. */ - tt_uint_op(tst->magic, OP_EQ, TEST_MAGIC); tt_str_op(tst->s, OP_EQ, "hello"); tt_ptr_op(tst->fn, OP_EQ, NULL); tt_int_op(tst->pos, OP_EQ, 0);