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Limit ASN.1 constructed types recursive definition depth

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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.

CVE-2018-0739

Credit to OSSFuzz for finding this issue.

Reviewed-by: Rich Salz <rsalz@openssl.org>
This commit is contained in:
Matt Caswell 2018-03-22 09:39:53 +00:00
parent faec5c4a8a
commit 4cabbb9f48
4 changed files with 37 additions and 16 deletions
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3
crypto/asn1/asn1_err.c
View file

@ -1,6 +1,6 @@
/*
* Generated by util/mkerr.pl DO NOT EDIT
* Copyright 1995-2017 The OpenSSL Project Authors. All Rights Reserved.
* Copyright 1995-2018 The OpenSSL Project Authors. All Rights Reserved.
*
* Licensed under the OpenSSL license (the "License"). You may not use
* this file except in compliance with the License. You can obtain a copy
@ -246,6 +246,7 @@ static const ERR_STRING_DATA ASN1_str_reasons[] = {
{ERR_PACK(ERR_LIB_ASN1, 0, ASN1_R_MSTRING_WRONG_TAG), "mstring wrong tag"},
{ERR_PACK(ERR_LIB_ASN1, 0, ASN1_R_NESTED_ASN1_STRING),
"nested asn1 string"},
{ERR_PACK(ERR_LIB_ASN1, 0, ASN1_R_NESTED_TOO_DEEP), "nested too deep"},
{ERR_PACK(ERR_LIB_ASN1, 0, ASN1_R_NON_HEX_CHARACTERS),
"non hex characters"},
{ERR_PACK(ERR_LIB_ASN1, 0, ASN1_R_NOT_ASCII_FORMAT), "not ascii format"},

48
crypto/asn1/tasn_dec.c
View file

@ -17,9 +17,19 @@
#include "internal/numbers.h"
#include "asn1_locl.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_item_embed_d2i(ASN1_VALUE **pval, const unsigned char **in,
long len, const ASN1_ITEM *it,
int tag, int aclass, char opt, ASN1_TLC *ctx);
int tag, int aclass, char opt, ASN1_TLC *ctx,
int depth);
static int asn1_check_eoc(const unsigned char **in, long len);
static int asn1_find_end(const unsigned char **in, long len, char inf);
@ -37,11 +47,11 @@ 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,
@ -111,7 +121,7 @@ int ASN1_item_ex_d2i(ASN1_VALUE **pval, const unsigned char **in, long len,
int tag, int aclass, char opt, ASN1_TLC *ctx)
{
int rv;
rv = asn1_item_embed_d2i(pval, in, len, it, tag, aclass, opt, ctx);
rv = asn1_item_embed_d2i(pval, in, len, it, tag, aclass, opt, ctx, 0);
if (rv <= 0)
ASN1_item_ex_free(pval, it);
return rv;
@ -124,7 +134,8 @@ int ASN1_item_ex_d2i(ASN1_VALUE **pval, const unsigned char **in, long len,
static int asn1_item_embed_d2i(ASN1_VALUE **pval, const unsigned char **in,
long len, const ASN1_ITEM *it,
int tag, int aclass, char opt, ASN1_TLC *ctx)
int tag, int aclass, char opt, ASN1_TLC *ctx,
int depth)
{
const ASN1_TEMPLATE *tt, *errtt = NULL;
const ASN1_EXTERN_FUNCS *ef;
@ -145,6 +156,11 @@ static int asn1_item_embed_d2i(ASN1_VALUE **pval, const unsigned char **in,
else
asn1_cb = 0;
if (++depth > ASN1_MAX_CONSTRUCTED_NEST) {
ASN1err(ASN1_F_ASN1_ITEM_EMBED_D2I, ASN1_R_NESTED_TOO_DEEP);
goto err;
}
switch (it->itype) {
case ASN1_ITYPE_PRIMITIVE:
if (it->templates) {
@ -160,7 +176,7 @@ static int asn1_item_embed_d2i(ASN1_VALUE **pval, const unsigned char **in,
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);
@ -221,7 +237,7 @@ static int asn1_item_embed_d2i(ASN1_VALUE **pval, const unsigned char **in,
/*
* 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;
@ -344,7 +360,8 @@ static int asn1_item_embed_d2i(ASN1_VALUE **pval, const unsigned char **in,
* 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;
@ -420,7 +437,7 @@ static int asn1_item_embed_d2i(ASN1_VALUE **pval, const unsigned char **in,
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;
@ -455,7 +472,7 @@ 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) {
ASN1err(ASN1_F_ASN1_TEMPLATE_EX_D2I, ERR_R_NESTED_ASN1_ERROR);
return 0;
@ -479,7 +496,7 @@ 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;
@ -491,7 +508,7 @@ 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;
@ -573,7 +590,8 @@ static int asn1_template_noexp_d2i(ASN1_VALUE **val,
}
skfield = NULL;
if (!asn1_item_embed_d2i(&skfield, &p, len,
ASN1_ITEM_ptr(tt->item), -1, 0, 0, ctx)) {
ASN1_ITEM_ptr(tt->item), -1, 0, 0, ctx,
depth)) {
ASN1err(ASN1_F_ASN1_TEMPLATE_NOEXP_D2I,
ERR_R_NESTED_ASN1_ERROR);
/* |skfield| may be partially allocated despite failure. */
@ -595,7 +613,7 @@ static int asn1_template_noexp_d2i(ASN1_VALUE **val,
/* IMPLICIT tagging */
ret = asn1_item_embed_d2i(val, &p, len,
ASN1_ITEM_ptr(tt->item), tt->tag, aclass, opt,
ctx);
ctx, depth);
if (!ret) {
ASN1err(ASN1_F_ASN1_TEMPLATE_NOEXP_D2I, ERR_R_NESTED_ASN1_ERROR);
goto err;
@ -604,7 +622,7 @@ static int asn1_template_noexp_d2i(ASN1_VALUE **val,
} else {
/* Nothing special */
ret = asn1_item_embed_d2i(val, &p, len, ASN1_ITEM_ptr(tt->item),
-1, 0, opt, ctx);
-1, 0, opt, ctx, depth);
if (!ret) {
ASN1err(ASN1_F_ASN1_TEMPLATE_NOEXP_D2I, ERR_R_NESTED_ASN1_ERROR);
goto err;

1
crypto/err/openssl.txt
View file

@ -1680,6 +1680,7 @@ ASN1_R_MISSING_VALUE:189:missing value
ASN1_R_MSTRING_NOT_UNIVERSAL:139:mstring not universal
ASN1_R_MSTRING_WRONG_TAG:140:mstring wrong tag
ASN1_R_NESTED_ASN1_STRING:197:nested asn1 string
ASN1_R_NESTED_TOO_DEEP:201:nested too deep
ASN1_R_NON_HEX_CHARACTERS:141:non hex characters
ASN1_R_NOT_ASCII_FORMAT:190:not ascii format
ASN1_R_NOT_ENOUGH_DATA:142:not enough data

1
include/openssl/asn1err.h
View file

@ -191,6 +191,7 @@ int ERR_load_ASN1_strings(void);
# define ASN1_R_MSTRING_NOT_UNIVERSAL 139
# define ASN1_R_MSTRING_WRONG_TAG 140
# define ASN1_R_NESTED_ASN1_STRING 197
# define ASN1_R_NESTED_TOO_DEEP 201
# define ASN1_R_NON_HEX_CHARACTERS 141
# define ASN1_R_NOT_ASCII_FORMAT 190
# define ASN1_R_NOT_ENOUGH_DATA 142