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Limit ASN.1 constructed types recursive definition depth

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Constructed types with a recursive definition could eventually exceed
the stack given malicious input with excessive recursion. Therefore we
limit the stack depth.

CVE-2018-0739

Credit to OSSFuzz for finding this issue.

(Imported from upstream's 9310d45087ae546e27e61ddf8f6367f29848220d.)

BoringSSL does not contain any such structures, but import this anyway
with a test.

Change-Id: I0e84578ea795134f25dae2ac8b565f3c26ef3204
Reviewed-on: https://boringssl-review.googlesource.com/26844
Commit-Queue: David Benjamin <davidben@google.com>
Commit-Queue: Adam Langley <agl@google.com>
Reviewed-by: Adam Langley <agl@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
This commit is contained in:
David Benjamin 2018-03-27 11:03:27 -04:00 committed by CQ bot account: commit-bot@chromium.org
parent 0970d397c4
commit 2a19a17ca7
4 changed files with 103 additions and 20 deletions
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62
crypto/asn1/asn1_test.cc
View File

@ -12,13 +12,18 @@
* OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
* CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
#include <limits.h>
#include <stdio.h>
#include <vector>
#include <gtest/gtest.h>
#include <limits.h>
#include <openssl/asn1.h>
#include <openssl/asn1t.h>
#include <openssl/bytestring.h>
#include <openssl/err.h>
#include <openssl/mem.h>
#include "../test/test_util.h"
@ -88,3 +93,58 @@ TEST(ASN1Test, IntegerSetting) {
}
}
}
typedef struct asn1_linked_list_st {
struct asn1_linked_list_st *next;
} ASN1_LINKED_LIST;
DECLARE_ASN1_ITEM(ASN1_LINKED_LIST)
DECLARE_ASN1_FUNCTIONS(ASN1_LINKED_LIST)
ASN1_SEQUENCE(ASN1_LINKED_LIST) = {
ASN1_OPT(ASN1_LINKED_LIST, next, ASN1_LINKED_LIST),
} ASN1_SEQUENCE_END(ASN1_LINKED_LIST)
IMPLEMENT_ASN1_FUNCTIONS(ASN1_LINKED_LIST)
static bool MakeLinkedList(bssl::UniquePtr<uint8_t> *out, size_t *out_len,
size_t count) {
bssl::ScopedCBB cbb;
std::vector<CBB> cbbs(count);
if (!CBB_init(cbb.get(), 2 * count) ||
!CBB_add_asn1(cbb.get(), &cbbs[0], CBS_ASN1_SEQUENCE)) {
return false;
}
for (size_t i = 1; i < count; i++) {
if (!CBB_add_asn1(&cbbs[i - 1], &cbbs[i], CBS_ASN1_SEQUENCE)) {
return false;
}
}
uint8_t *ptr;
if (!CBB_finish(cbb.get(), &ptr, out_len)) {
return false;
}
out->reset(ptr);
return true;
}
TEST(ASN1Test, Recursive) {
bssl::UniquePtr<uint8_t> data;
size_t len;
// Sanity-check that MakeLinkedList can be parsed.
ASSERT_TRUE(MakeLinkedList(&data, &len, 5));
const uint8_t *ptr = data.get();
ASN1_LINKED_LIST *list = d2i_ASN1_LINKED_LIST(nullptr, &ptr, len);
EXPECT_TRUE(list);
ASN1_LINKED_LIST_free(list);
// Excessively deep structures are rejected.
ASSERT_TRUE(MakeLinkedList(&data, &len, 100));
ptr = data.get();
list = d2i_ASN1_LINKED_LIST(nullptr, &ptr, len);
EXPECT_FALSE(list);
// Note checking the error queue here does not work. The error "stack trace"
// is too deep, so the |ASN1_R_NESTED_TOO_DEEP| entry drops off the queue.
ASN1_LINKED_LIST_free(list);
}

59
crypto/asn1/tasn_dec.c
View File

@ -66,6 +66,14 @@
#include "../internal.h"
/*
* Constructed types with a recursive definition (such as can be found in PKCS7)
* could eventually exceed the stack given malicious input with excessive
* recursion. Therefore we limit the stack depth. This is the maximum number of
* recursive invocations of asn1_item_embed_d2i().
*/
#define ASN1_MAX_CONSTRUCTED_NEST 30
static int asn1_check_eoc(const unsigned char **in, long len);
static int asn1_find_end(const unsigned char **in, long len, char inf);
@ -82,11 +90,11 @@ static int asn1_check_tlen(long *olen, int *otag, unsigned char *oclass,
static int asn1_template_ex_d2i(ASN1_VALUE **pval,
const unsigned char **in, long len,
const ASN1_TEMPLATE *tt, char opt,
ASN1_TLC *ctx);
ASN1_TLC *ctx, int depth);
static int asn1_template_noexp_d2i(ASN1_VALUE **val,
const unsigned char **in, long len,
const ASN1_TEMPLATE *tt, char opt,
ASN1_TLC *ctx);
ASN1_TLC *ctx, int depth);
static int asn1_d2i_ex_primitive(ASN1_VALUE **pval,
const unsigned char **in, long len,
const ASN1_ITEM *it,
@ -153,9 +161,9 @@ ASN1_VALUE *ASN1_item_d2i(ASN1_VALUE **pval,
* tag mismatch return -1 to handle OPTIONAL
*/
int ASN1_item_ex_d2i(ASN1_VALUE **pval, const unsigned char **in, long len,
const ASN1_ITEM *it,
int tag, int aclass, char opt, ASN1_TLC *ctx)
static int asn1_item_ex_d2i(ASN1_VALUE **pval, const unsigned char **in,
long len, const ASN1_ITEM *it, int tag, int aclass,
char opt, ASN1_TLC *ctx, int depth)
{
const ASN1_TEMPLATE *tt, *errtt = NULL;
const ASN1_COMPAT_FUNCS *cf;
@ -188,6 +196,11 @@ int ASN1_item_ex_d2i(ASN1_VALUE **pval, const unsigned char **in, long len,
len = INT_MAX/2;
}
if (++depth > ASN1_MAX_CONSTRUCTED_NEST) {
OPENSSL_PUT_ERROR(ASN1, ASN1_R_NESTED_TOO_DEEP);
goto err;
}
switch (it->itype) {
case ASN1_ITYPE_PRIMITIVE:
if (it->templates) {
@ -203,7 +216,7 @@ int ASN1_item_ex_d2i(ASN1_VALUE **pval, const unsigned char **in, long len,
goto err;
}
return asn1_template_ex_d2i(pval, in, len,
it->templates, opt, ctx);
it->templates, opt, ctx, depth);
}
return asn1_d2i_ex_primitive(pval, in, len, it,
tag, aclass, opt, ctx);
@ -326,7 +339,7 @@ int ASN1_item_ex_d2i(ASN1_VALUE **pval, const unsigned char **in, long len,
/*
* We mark field as OPTIONAL so its absence can be recognised.
*/
ret = asn1_template_ex_d2i(pchptr, &p, len, tt, 1, ctx);
ret = asn1_template_ex_d2i(pchptr, &p, len, tt, 1, ctx, depth);
/* If field not present, try the next one */
if (ret == -1)
continue;
@ -444,7 +457,8 @@ int ASN1_item_ex_d2i(ASN1_VALUE **pval, const unsigned char **in, long len,
* attempt to read in field, allowing each to be OPTIONAL
*/
ret = asn1_template_ex_d2i(pseqval, &p, len, seqtt, isopt, ctx);
ret = asn1_template_ex_d2i(pseqval, &p, len, seqtt, isopt, ctx,
depth);
if (!ret) {
errtt = seqtt;
goto err;
@ -514,6 +528,13 @@ int ASN1_item_ex_d2i(ASN1_VALUE **pval, const unsigned char **in, long len,
return 0;
}
int ASN1_item_ex_d2i(ASN1_VALUE **pval, const unsigned char **in, long len,
const ASN1_ITEM *it,
int tag, int aclass, char opt, ASN1_TLC *ctx)
{
return asn1_item_ex_d2i(pval, in, len, it, tag, aclass, opt, ctx, 0);
}
/*
* Templates are handled with two separate functions. One handles any
* EXPLICIT tag and the other handles the rest.
@ -522,7 +543,7 @@ int ASN1_item_ex_d2i(ASN1_VALUE **pval, const unsigned char **in, long len,
static int asn1_template_ex_d2i(ASN1_VALUE **val,
const unsigned char **in, long inlen,
const ASN1_TEMPLATE *tt, char opt,
ASN1_TLC *ctx)
ASN1_TLC *ctx, int depth)
{
int flags, aclass;
int ret;
@ -556,7 +577,7 @@ static int asn1_template_ex_d2i(ASN1_VALUE **val,
return 0;
}
/* We've found the field so it can't be OPTIONAL now */
ret = asn1_template_noexp_d2i(val, &p, len, tt, 0, ctx);
ret = asn1_template_noexp_d2i(val, &p, len, tt, 0, ctx, depth);
if (!ret) {
OPENSSL_PUT_ERROR(ASN1, ASN1_R_NESTED_ASN1_ERROR);
return 0;
@ -579,7 +600,7 @@ static int asn1_template_ex_d2i(ASN1_VALUE **val,
}
}
} else
return asn1_template_noexp_d2i(val, in, inlen, tt, opt, ctx);
return asn1_template_noexp_d2i(val, in, inlen, tt, opt, ctx, depth);
*in = p;
return 1;
@ -592,7 +613,7 @@ static int asn1_template_ex_d2i(ASN1_VALUE **val,
static int asn1_template_noexp_d2i(ASN1_VALUE **val,
const unsigned char **in, long len,
const ASN1_TEMPLATE *tt, char opt,
ASN1_TLC *ctx)
ASN1_TLC *ctx, int depth)
{
int flags, aclass;
int ret;
@ -661,8 +682,8 @@ static int asn1_template_noexp_d2i(ASN1_VALUE **val,
break;
}
skfield = NULL;
if (!ASN1_item_ex_d2i(&skfield, &p, len,
ASN1_ITEM_ptr(tt->item), -1, 0, 0, ctx)) {
if (!asn1_item_ex_d2i(&skfield, &p, len, ASN1_ITEM_ptr(tt->item),
-1, 0, 0, ctx, depth)) {
OPENSSL_PUT_ERROR(ASN1, ASN1_R_NESTED_ASN1_ERROR);
goto err;
}
@ -679,9 +700,8 @@ static int asn1_template_noexp_d2i(ASN1_VALUE **val,
}
} else if (flags & ASN1_TFLG_IMPTAG) {
/* IMPLICIT tagging */
ret = ASN1_item_ex_d2i(val, &p, len,
ASN1_ITEM_ptr(tt->item), tt->tag, aclass, opt,
ctx);
ret = asn1_item_ex_d2i(val, &p, len, ASN1_ITEM_ptr(tt->item), tt->tag,
aclass, opt, ctx, depth);
if (!ret) {
OPENSSL_PUT_ERROR(ASN1, ASN1_R_NESTED_ASN1_ERROR);
goto err;
@ -689,8 +709,9 @@ static int asn1_template_noexp_d2i(ASN1_VALUE **val,
return -1;
} else {
/* Nothing special */
ret = ASN1_item_ex_d2i(val, &p, len, ASN1_ITEM_ptr(tt->item),
-1, tt->flags & ASN1_TFLG_COMBINE, opt, ctx);
ret = asn1_item_ex_d2i(val, &p, len, ASN1_ITEM_ptr(tt->item),
-1, tt->flags & ASN1_TFLG_COMBINE, opt, ctx,
depth);
if (!ret) {
OPENSSL_PUT_ERROR(ASN1, ASN1_R_NESTED_ASN1_ERROR);
goto err;

1
crypto/err/asn1.errordata
View File

@ -58,6 +58,7 @@ ASN1,156,MSTRING_NOT_UNIVERSAL
ASN1,157,MSTRING_WRONG_TAG
ASN1,158,NESTED_ASN1_ERROR
ASN1,159,NESTED_ASN1_STRING
ASN1,192,NESTED_TOO_DEEP
ASN1,160,NON_HEX_CHARACTERS
ASN1,161,NOT_ASCII_FORMAT
ASN1,162,NOT_ENOUGH_DATA

1
include/openssl/asn1.h
View File

@ -976,5 +976,6 @@ BORINGSSL_MAKE_DELETER(ASN1_TYPE, ASN1_TYPE_free)
#define ASN1_R_WRONG_PUBLIC_KEY_TYPE 189
#define ASN1_R_WRONG_TAG 190
#define ASN1_R_WRONG_TYPE 191
#define ASN1_R_NESTED_TOO_DEEP 192
#endif