Commit c6298139 authored by Dr. Stephen Henson's avatar Dr. Stephen Henson
Browse files

Harden ASN.1 BIO handling of large amounts of data. 



If the ASN.1 BIO is presented with a large length field read it in
chunks of increasing size checking for EOF on each read. This prevents
small files allocating excessive amounts of data.

CVE-2016-2109

Thanks to Brian Carpenter for reporting this issue.

Reviewed-by: default avatarViktor Dukhovni <viktor@openssl.org>
parent ddc606c9

crypto/asn1/a_d2i_fp.c

+26 −10
Original line number Diff line number Diff line
@@ -138,6 +138,7 @@ void *ASN1_item_d2i_fp(const ASN1_ITEM *it, FILE *in, void *x) 
#endif



#define HEADER_SIZE   8

#define ASN1_CHUNK_INITIAL_SIZE (16 * 1024)

static int asn1_d2i_read_bio(BIO *in, BUF_MEM **pb)

{

    BUF_MEM *b;
@@ -216,18 +217,30 @@ static int asn1_d2i_read_bio(BIO *in, BUF_MEM **pb) 
            /* suck in slen bytes of data */

            want = slen;

            if (want > (len - off)) {

                size_t chunk_max = ASN1_CHUNK_INITIAL_SIZE;



                want -= (len - off);

                if (want > INT_MAX /* BIO_read takes an int length */  ||

                    len + want < len) {

                    ASN1err(ASN1_F_ASN1_D2I_READ_BIO, ASN1_R_TOO_LONG);

                    goto err;

                }

                if (!BUF_MEM_grow_clean(b, len + want)) {

                while (want > 0) {

                    /*

                     * Read content in chunks of increasing size

                     * so we can return an error for EOF without

                     * having to allocate the entire content length

                     * in one go.

                     */

                    size_t chunk = want > chunk_max ? chunk_max : want;



                    if (!BUF_MEM_grow_clean(b, len + chunk)) {

                        ASN1err(ASN1_F_ASN1_D2I_READ_BIO, ERR_R_MALLOC_FAILURE);

                        goto err;

                    }

                while (want > 0) {

                    i = BIO_read(in, &(b->data[len]), want);

                    want -= chunk;

                    while (chunk > 0) {

                        i = BIO_read(in, &(b->data[len]), chunk);

                        if (i <= 0) {

                            ASN1err(ASN1_F_ASN1_D2I_READ_BIO,

                                    ASN1_R_NOT_ENOUGH_DATA);
@@ -238,7 +251,10 @@ static int asn1_d2i_read_bio(BIO *in, BUF_MEM **pb) 
                     * overflow.

                     */

                        len += i;

                    want -= i;

                        chunk -= i;

                    }

                    if (chunk_max < INT_MAX/2)

                        chunk_max *= 2;

                }

            }

            if (off + slen < off) {