Commit 2ac4c6f7 authored by Matt Caswell's avatar Matt Caswell
Browse files

Limit ASN.1 constructed types recursive definition depth 



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: default avatarRich Salz <rsalz@openssl.org>
parent d8278dac

crypto/asn1/asn1_err.c

+2 −1
Original line number Diff line number Diff line 
/*

 * 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
@@ -203,6 +203,7 @@ static ERR_STRING_DATA ASN1_str_reasons[] = { 
    {ERR_REASON(ASN1_R_MSTRING_NOT_UNIVERSAL), "mstring not universal"},

    {ERR_REASON(ASN1_R_MSTRING_WRONG_TAG), "mstring wrong tag"},

    {ERR_REASON(ASN1_R_NESTED_ASN1_STRING), "nested asn1 string"},

    {ERR_REASON(ASN1_R_NESTED_TOO_DEEP), "nested too deep"},

    {ERR_REASON(ASN1_R_NON_HEX_CHARACTERS), "non hex characters"},

    {ERR_REASON(ASN1_R_NOT_ASCII_FORMAT), "not ascii format"},

    {ERR_REASON(ASN1_R_NOT_ENOUGH_DATA), "not enough data"},

crypto/asn1/tasn_dec.c

+32 −15
Original line number Diff line number Diff line
@@ -17,9 +17,18 @@ 
#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 +46,11 @@ 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 +120,7 @@ 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 +133,8 @@ 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 +155,11 @@ 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 +175,7 @@ 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 +236,7 @@ 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 +359,8 @@ 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 +436,7 @@ 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 +471,7 @@ 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 +495,7 @@ 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 +507,7 @@ 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 +589,8 @@ 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 +612,7 @@ 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 +621,7 @@ 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;

include/openssl/asn1.h

+1 −0
Original line number Diff line number Diff line
@@ -1051,6 +1051,7 @@ 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