/* $OpenBSD: tasn_dec.c,v 1.89 2025/05/10 05:54:38 tb Exp $ */
/* Written by Dr Stephen N Henson (steve@openssl.org) for the OpenSSL
 * project 2000.
 */
/* ====================================================================
 * Copyright (c) 2000-2005 The OpenSSL Project.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. All advertising materials mentioning features or use of this
 *    software must display the following acknowledgment:
 *    "This product includes software developed by the OpenSSL Project
 *    for use in the OpenSSL Toolkit. (http://www.OpenSSL.org/)"
 *
 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission. For written permission, please contact
 *    licensing@OpenSSL.org.
 *
 * 5. Products derived from this software may not be called "OpenSSL"
 *    nor may "OpenSSL" appear in their names without prior written
 *    permission of the OpenSSL Project.
 *
 * 6. Redistributions of any form whatsoever must retain the following
 *    acknowledgment:
 *    "This product includes software developed by the OpenSSL Project
 *    for use in the OpenSSL Toolkit (http://www.OpenSSL.org/)"
 *
 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 * ====================================================================
 *
 * This product includes cryptographic software written by Eric Young
 * (eay@cryptsoft.com).  This product includes software written by Tim
 * Hudson (tjh@cryptsoft.com).
 *
 */

#include <limits.h>
#include <stddef.h>
#include <string.h>

#include <openssl/asn1.h>
#include <openssl/asn1t.h>
#include <openssl/buffer.h>
#include <openssl/objects.h>

#include "asn1_local.h"
#include "bytestring.h"
#include "err_local.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.
 */
#define ASN1_MAX_CONSTRUCTED_NEST 30

#ifndef ASN1_MAX_STRING_NEST
/*
 * This determines how many levels of recursion are permitted in ASN.1 string
 * types. If it is not limited stack overflows can occur. If set to zero no
 * recursion is allowed at all.
 */
#define ASN1_MAX_STRING_NEST 5
#endif

static int asn1_template_d2i(ASN1_VALUE **pval, CBS *cbs,
    const ASN1_TEMPLATE *at, int optional, int depth);

static int
asn1_check_eoc(CBS *cbs)
{
        uint16_t eoc;

        if (!CBS_peek_u16(cbs, &eoc))
                return 0;
        if (eoc != 0)
                return 0;

        return CBS_skip(cbs, 2);
}

static int
asn1_check_tag(CBS *cbs, size_t *out_len, int *out_tag, uint8_t *out_class,
    int *out_indefinite, int *out_constructed, int expected_tag,
    int expected_class, int optional)
{
        int constructed, indefinite;
        uint32_t tag_number;
        uint8_t tag_class;
        size_t length;

        if (out_len != NULL)
                *out_len = 0;
        if (out_tag != NULL)
                *out_tag = 0;
        if (out_class != NULL)
                *out_class = 0;
        if (out_indefinite != NULL)
                *out_indefinite = 0;
        if (out_constructed != NULL)
                *out_constructed = 0;

        if (!asn1_get_identifier_cbs(cbs, 0, &tag_class, &constructed,
            &tag_number)) {
                ASN1error(ASN1_R_BAD_OBJECT_HEADER);
                return 0;
        }
        if (expected_tag >= 0) {
                if (expected_tag != tag_number ||
                    expected_class != tag_class << 6) {
                        /* Indicate missing type if this is OPTIONAL. */
                        if (optional)
                                return -1;

                        ASN1error(ASN1_R_WRONG_TAG);
                        return 0;
                }
        }
        if (!asn1_get_length_cbs(cbs, 0, &indefinite, &length)) {
                ASN1error(ASN1_R_BAD_OBJECT_HEADER);
                return 0;
        }

        /* Indefinite length can only be used with constructed encoding. */
        if (indefinite && !constructed) {
                ASN1error(ASN1_R_BAD_OBJECT_HEADER);
                return 0;
        }

        if (!indefinite && CBS_len(cbs) < length) {
                ASN1error(ASN1_R_TOO_LONG);
                return 0;
        }

        if (tag_number > INT_MAX) {
                ASN1error(ASN1_R_TOO_LONG);
                return 0;
        }

        if (indefinite)
                length = CBS_len(cbs);

        if (out_len != NULL)
                *out_len = length;
        if (out_tag != NULL)
                *out_tag = tag_number;
        if (out_class != NULL)
                *out_class = tag_class << 6;
        if (out_indefinite != NULL)
                *out_indefinite = indefinite;
        if (out_constructed != NULL)
                *out_constructed = constructed;

        return 1;
}

/* Collect the contents from a constructed ASN.1 object. */
static int
asn1_collect(CBB *cbb, CBS *cbs, int indefinite, int expected_tag,
    int expected_class, int depth)
{
        int constructed;
        size_t length;
        CBS content;
        int need_eoc;

        if (depth > ASN1_MAX_STRING_NEST) {
                ASN1error(ASN1_R_NESTED_ASN1_STRING);
                return 0;
        }

        need_eoc = indefinite;

        while (CBS_len(cbs) > 0) {
                if (asn1_check_eoc(cbs)) {
                        if (!need_eoc) {
                                ASN1error(ASN1_R_UNEXPECTED_EOC);
                                return 0;
                        }
                        return 1;
                }
                if (!asn1_check_tag(cbs, &length, NULL, NULL, &indefinite,
                    &constructed, expected_tag, expected_class, 0)) {
                        ASN1error(ERR_R_NESTED_ASN1_ERROR);
                        return 0;
                }

                if (constructed) {
                        if (!asn1_collect(cbb, cbs, indefinite, expected_tag,
                            expected_class, depth + 1))
                                return 0;
                        continue;
                }

                if (!CBS_get_bytes(cbs, &content, length)) {
                        ASN1error(ERR_R_NESTED_ASN1_ERROR);
                        return 0;
                }
                if (!CBB_add_bytes(cbb, CBS_data(&content), CBS_len(&content)))
                        return 0;
        }

        if (need_eoc) {
                ASN1error(ASN1_R_MISSING_EOC);
                return 0;
        }

        return 1;
}

/* Find the end of an ASN.1 object. */
static int
asn1_find_end(CBS *cbs, size_t length, int indefinite)
{
        size_t eoc_count;

        if (!indefinite) {
                if (!CBS_skip(cbs, length)) {
                        ASN1error(ERR_R_NESTED_ASN1_ERROR);
                        return 0;
                }
                return 1;
        }

        eoc_count = 1;

        while (CBS_len(cbs) > 0) {
                if (asn1_check_eoc(cbs)) {
                        if (--eoc_count == 0)
                                break;
                        continue;
                }
                if (!asn1_check_tag(cbs, &length, NULL, NULL,
                    &indefinite, NULL, -1, 0, 0)) {
                        ASN1error(ERR_R_NESTED_ASN1_ERROR);
                        return 0;
                }
                if (indefinite) {
                        eoc_count++;
                        continue;
                }
                if (!CBS_skip(cbs, length))
                        return 0;
        }

        if (eoc_count > 0) {
                ASN1error(ASN1_R_MISSING_EOC);
                return 0;
        }

        return 1;
}

static int
asn1_c2i_primitive(ASN1_VALUE **pval, CBS *content, int utype, const ASN1_ITEM *it)
{
        ASN1_BOOLEAN *abool;
        ASN1_STRING *astr;
        uint8_t val;
        int ret = 0;

        if (it->funcs != NULL)
                goto err;

        if (CBS_len(content) > INT_MAX)
                goto err;

        switch (utype) {
        case V_ASN1_OBJECT:
                if (!c2i_ASN1_OBJECT_cbs((ASN1_OBJECT **)pval, content))
                        goto err;
                break;

        case V_ASN1_NULL:
                if (CBS_len(content) != 0) {
                        ASN1error(ASN1_R_NULL_IS_WRONG_LENGTH);
                        goto err;
                }
                *pval = (ASN1_VALUE *)1;
                break;

        case V_ASN1_BOOLEAN:
                abool = (ASN1_BOOLEAN *)pval;
                if (CBS_len(content) != 1) {
                        ASN1error(ASN1_R_BOOLEAN_IS_WRONG_LENGTH);
                        goto err;
                }
                if (!CBS_get_u8(content, &val))
                        goto err;
                *abool = val;
                break;

        case V_ASN1_BIT_STRING:
                if (!c2i_ASN1_BIT_STRING_cbs((ASN1_BIT_STRING **)pval, content))
                        goto err;
                break;

        case V_ASN1_ENUMERATED:
                if (!c2i_ASN1_ENUMERATED_cbs((ASN1_ENUMERATED **)pval, content))
                        goto err;
                break;

        case V_ASN1_INTEGER:
                if (!c2i_ASN1_INTEGER_cbs((ASN1_INTEGER **)pval, content))
                        goto err;
                break;

        case V_ASN1_OCTET_STRING:
        case V_ASN1_NUMERICSTRING:
        case V_ASN1_PRINTABLESTRING:
        case V_ASN1_T61STRING:
        case V_ASN1_VIDEOTEXSTRING:
        case V_ASN1_IA5STRING:
        case V_ASN1_UTCTIME:
        case V_ASN1_GENERALIZEDTIME:
        case V_ASN1_GRAPHICSTRING:
        case V_ASN1_VISIBLESTRING:
        case V_ASN1_GENERALSTRING:
        case V_ASN1_UNIVERSALSTRING:
        case V_ASN1_BMPSTRING:
        case V_ASN1_UTF8STRING:
        case V_ASN1_OTHER:
        case V_ASN1_SET:
        case V_ASN1_SEQUENCE:
        default:
                if (utype == V_ASN1_BMPSTRING && (CBS_len(content) & 1)) {
                        ASN1error(ASN1_R_BMPSTRING_IS_WRONG_LENGTH);
                        goto err;
                }
                if (utype == V_ASN1_UNIVERSALSTRING && (CBS_len(content) & 3)) {
                        ASN1error(ASN1_R_UNIVERSALSTRING_IS_WRONG_LENGTH);
                        goto err;
                }
                if (utype == V_ASN1_UTCTIME || utype == V_ASN1_GENERALIZEDTIME) {
                        if (!asn1_time_parse_cbs(content,
                            utype == V_ASN1_GENERALIZEDTIME, NULL))  {
                                ASN1error(ASN1_R_INVALID_TIME_FORMAT);
                                goto err;
                        }
                }
                /* All based on ASN1_STRING and handled the same way. */
                if (*pval != NULL) {
                        ASN1_STRING_free((ASN1_STRING *)*pval);
                        *pval = NULL;
                }
                if ((astr = ASN1_STRING_type_new(utype)) == NULL) {
                        ASN1error(ERR_R_MALLOC_FAILURE);
                        goto err;
                }
                if (!ASN1_STRING_set(astr, CBS_data(content), CBS_len(content))) {
                        ASN1_STRING_free(astr);
                        goto err;
                }
                *pval = (ASN1_VALUE *)astr;
                break;
        }

        ret = 1;

 err:
        return ret;
}

static int
asn1_c2i_any(ASN1_VALUE **pval, CBS *content, int utype, const ASN1_ITEM *it)
{
        ASN1_TYPE *atype;

        if (it->utype != V_ASN1_ANY || it->funcs != NULL)
                return 0;

        if (*pval != NULL) {
                ASN1_TYPE_free((ASN1_TYPE *)*pval);
                *pval = NULL;
        }

        if ((atype = ASN1_TYPE_new()) == NULL)
                return 0;

        if (!asn1_c2i_primitive(&atype->value.asn1_value, content, utype, it)) {
                ASN1_TYPE_free(atype);
                return 0;
        }
        atype->type = utype;

        /* Fix up value for ASN.1 NULL. */
        if (atype->type == V_ASN1_NULL)
                atype->value.ptr = NULL;

        *pval = (ASN1_VALUE *)atype;

        return 1;
}

static int
asn1_c2i(ASN1_VALUE **pval, CBS *content, int utype, const ASN1_ITEM *it)
{
        if (CBS_len(content) > INT_MAX)
                return 0;

        if (it->funcs != NULL) {
                const ASN1_PRIMITIVE_FUNCS *pf = it->funcs;
                char free_content = 0;

                if (pf->prim_c2i == NULL)
                        return 0;

                return pf->prim_c2i(pval, CBS_data(content), CBS_len(content),
                    utype, &free_content, it);
        }

        if (it->utype == V_ASN1_ANY)
                return asn1_c2i_any(pval, content, utype, it);

        return asn1_c2i_primitive(pval, content, utype, it);
}

/*
 * Decode ASN.1 content into a primitive type. There are three possible forms -
 * a SEQUENCE/SET/OTHER that is stored verbatim (including the ASN.1 tag and
 * length octets), constructed objects and non-constructed objects. In the
 * first two cases indefinite length is permitted, which we may need to handle.
 * When this function is called the *cbs should reference the start of the
 * ASN.1 object (i.e. the tag/length header), while *cbs_object should
 * reference the start of the object contents (i.e. after the tag/length
 * header. Additionally, the *cbs_object offset should be relative to the
 * ASN.1 object being parsed. On success the *cbs will point at the octet
 * after the object.
 */
static int
asn1_d2i_primitive_content(ASN1_VALUE **pval, CBS *cbs, CBS *cbs_object,
    int utype, int constructed, int indefinite, size_t length,
    const ASN1_ITEM *it)
{
        CBS cbs_content, cbs_initial;
        uint8_t *data = NULL;
        size_t data_len = 0;
        CBB cbb;
        int ret = 0;

        memset(&cbb, 0, sizeof(cbb));

        CBS_dup(cbs, &cbs_initial);
        CBS_init(&cbs_content, NULL, 0);

        if (asn1_must_be_constructed(utype) && !constructed) {
                ASN1error(ASN1_R_TYPE_NOT_CONSTRUCTED);
                goto err;
        }
        if (asn1_must_be_primitive(utype) && constructed) {
                ASN1error(ASN1_R_TYPE_NOT_PRIMITIVE);
                goto err;
        }

        /* SEQUENCE, SET and "OTHER" are left in encoded form. */
        if (utype == V_ASN1_SEQUENCE || utype == V_ASN1_SET ||
            utype == V_ASN1_OTHER) {
                if (!asn1_find_end(cbs_object, length, indefinite))
                        goto err;
                if (!CBS_get_bytes(&cbs_initial, &cbs_content,
                    CBS_offset(cbs_object)))
                        goto err;
        } else if (constructed) {
                /*
                 * Should really check the internal tags are correct but
                 * some things may get this wrong. The relevant specs
                 * say that constructed string types should be OCTET STRINGs
                 * internally irrespective of the type. So instead just check
                 * for UNIVERSAL class and ignore the tag.
                 */
                if (!CBB_init(&cbb, 0))
                        goto err;
                if (!asn1_collect(&cbb, cbs_object, indefinite, -1,
                    V_ASN1_UNIVERSAL, 0))
                        goto err;
                if (!CBB_finish(&cbb, &data, &data_len))
                        goto err;

                CBS_init(&cbs_content, data, data_len);
        } else {
                if (!CBS_get_bytes(cbs_object, &cbs_content, length))
                        goto err;
        }

        if (!asn1_c2i(pval, &cbs_content, utype, it))
                goto err;

        if (!CBS_skip(cbs, CBS_offset(cbs_object)))
                goto err;

        ret = 1;

 err:
        CBB_cleanup(&cbb);
        freezero(data, data_len);

        return ret;
}

static int
asn1_d2i_any(ASN1_VALUE **pval, CBS *cbs, const ASN1_ITEM *it,
    int tag_number, int tag_class, int optional)
{
        int constructed, indefinite;
        uint8_t object_class;
        int object_type;
        CBS cbs_object;
        size_t length;

        CBS_init(&cbs_object, CBS_data(cbs), CBS_len(cbs));

        if (it->utype != V_ASN1_ANY)
                return 0;

        if (tag_number >= 0) {
                ASN1error(ASN1_R_ILLEGAL_TAGGED_ANY);
                return 0;
        }
        if (optional) {
                ASN1error(ASN1_R_ILLEGAL_OPTIONAL_ANY);
                return 0;
        }

        /* Determine type from ASN.1 tag. */
        if (asn1_check_tag(&cbs_object, &length, &object_type, &object_class,
            &indefinite, &constructed, -1, 0, 0) != 1) {
                ASN1error(ERR_R_NESTED_ASN1_ERROR);
                return 0;
        }
        if (object_class != V_ASN1_UNIVERSAL)
                object_type = V_ASN1_OTHER;

        return asn1_d2i_primitive_content(pval, cbs, &cbs_object, object_type,
            constructed, indefinite, length, it);
}

static int
asn1_d2i_mstring(ASN1_VALUE **pval, CBS *cbs, const ASN1_ITEM *it,
    int tag_number, int tag_class, int optional)
{
        int constructed, indefinite;
        uint8_t object_class;
        int object_tag;
        CBS cbs_object;
        size_t length;

        CBS_init(&cbs_object, CBS_data(cbs), CBS_len(cbs));

        /*
         * It never makes sense for multi-strings to have implicit tagging, so
         * if tag_number != -1, then this looks like an error in the template.
         */
        if (tag_number != -1) {
                ASN1error(ASN1_R_BAD_TEMPLATE);
                return 0;
        }

        if (asn1_check_tag(&cbs_object, &length, &object_tag, &object_class,
            &indefinite, &constructed, -1, 0, 1) != 1) {
                ASN1error(ERR_R_NESTED_ASN1_ERROR);
                return 0;
        }

        /* Class must be UNIVERSAL. */
        if (object_class != V_ASN1_UNIVERSAL) {
                if (optional)
                        return -1;
                ASN1error(ASN1_R_MSTRING_NOT_UNIVERSAL);
                return 0;
        }
        /* Check tag matches bit map. */
        if ((ASN1_tag2bit(object_tag) & it->utype) == 0) {
                if (optional)
                        return -1;
                ASN1error(ASN1_R_MSTRING_WRONG_TAG);
                return 0;
        }

        return asn1_d2i_primitive_content(pval, cbs, &cbs_object,
            object_tag, constructed, indefinite, length, it);
}

static int
asn1_d2i_primitive(ASN1_VALUE **pval, CBS *cbs, const ASN1_ITEM *it,
    int tag_number, int tag_class, int optional)
{
        CBS cbs_object;
        int constructed, indefinite;
        int utype = it->utype;
        size_t length;
        int ret;

        CBS_init(&cbs_object, CBS_data(cbs), CBS_len(cbs));

        if (it->itype == ASN1_ITYPE_MSTRING)
                return 0;

        if (it->utype == V_ASN1_ANY)
                return asn1_d2i_any(pval, cbs, it, tag_number, tag_class, optional);

        if (tag_number == -1) {
                tag_number = it->utype;
                tag_class = V_ASN1_UNIVERSAL;
        }

        ret = asn1_check_tag(&cbs_object, &length, NULL, NULL, &indefinite,
            &constructed, tag_number, tag_class, optional);
        if (ret == -1)
                return -1;
        if (ret != 1) {
                ASN1error(ERR_R_NESTED_ASN1_ERROR);
                return 0;
        }

        return asn1_d2i_primitive_content(pval, cbs, &cbs_object, utype,
            constructed, indefinite, length, it);
}

static int
asn1_item_d2i_choice(ASN1_VALUE **pval, CBS *cbs, const ASN1_ITEM *it,
    int tag_number, int tag_class, int optional, int depth)
{
        const ASN1_TEMPLATE *at, *errat = NULL;
        const ASN1_AUX *aux;
        ASN1_aux_cb *asn1_cb = NULL;
        ASN1_VALUE *achoice = NULL;
        ASN1_VALUE **pchptr;
        int i, ret;

        if ((aux = it->funcs) != NULL)
                asn1_cb = aux->asn1_cb;

        if (it->itype != ASN1_ITYPE_CHOICE)
                goto err;

        /*
         * It never makes sense for CHOICE types to have implicit tagging, so
         * if tag_number != -1, then this looks like an error in the template.
         */
        if (tag_number != -1) {
                ASN1error(ASN1_R_BAD_TEMPLATE);
                goto err;
        }

        if (*pval != NULL) {
                ASN1_item_ex_free(pval, it);
                *pval = NULL;
        }

        if (!ASN1_item_ex_new(&achoice, it)) {
                ASN1error(ERR_R_NESTED_ASN1_ERROR);
                goto err;
        }

        if (asn1_cb != NULL && !asn1_cb(ASN1_OP_D2I_PRE, &achoice, it, NULL)) {
                ASN1error(ASN1_R_AUX_ERROR);
                goto err;
        }

        /* Try each possible CHOICE in turn. */
        for (i = 0; i < it->tcount; i++) {
                at = &it->templates[i];

                pchptr = asn1_get_field_ptr(&achoice, at);

                /* Mark field as OPTIONAL so its absence can be identified. */
                ret = asn1_template_d2i(pchptr, cbs, at, 1, depth);
                if (ret == -1)
                        continue;
                if (ret != 1) {
                        ASN1error(ERR_R_NESTED_ASN1_ERROR);
                        errat = at;
                        goto err;
                }

                /* We've successfully decoded an ASN.1 object. */
                asn1_set_choice_selector(&achoice, i, it);
                break;
        }

        /* Did we fall off the end without reading anything? */
        if (i == it->tcount) {
                if (optional) {
                        ASN1_item_ex_free(&achoice, it);
                        return -1;
                }
                ASN1error(ASN1_R_NO_MATCHING_CHOICE_TYPE);
                goto err;
        }

        if (asn1_cb != NULL && !asn1_cb(ASN1_OP_D2I_POST, &achoice, it, NULL)) {
                ASN1error(ASN1_R_AUX_ERROR);
                goto err;
        }

        *pval = achoice;
        achoice = NULL;

        return 1;

 err:
        ASN1_item_ex_free(&achoice, it);

        if (errat != NULL)
                ERR_asprintf_error_data("Field=%s, Type=%s", errat->field_name,
                    it->sname);
        else
                ERR_asprintf_error_data("Type=%s", it->sname);

        return 0;
}

static int
asn1_item_d2i_sequence(ASN1_VALUE **pval, CBS *cbs, const ASN1_ITEM *it,
    int tag_number, int tag_class, int optional, int depth)
{
        CBS cbs_seq, cbs_seq_content, cbs_object;
        int constructed, indefinite, optional_field;
        const ASN1_TEMPLATE *errat = NULL;
        const ASN1_TEMPLATE *seqat, *at;
        ASN1_aux_cb *asn1_cb = NULL;
        const ASN1_AUX *aux;
        ASN1_VALUE *aseq = NULL;
        ASN1_VALUE **pseqval;
        int eoc_needed, i;
        size_t length;
        int ret = 0;

        CBS_init(&cbs_seq, CBS_data(cbs), CBS_len(cbs));

        if ((aux = it->funcs) != NULL)
                asn1_cb = aux->asn1_cb;

        if (it->itype != ASN1_ITYPE_NDEF_SEQUENCE &&
            it->itype != ASN1_ITYPE_SEQUENCE)
                goto err;

        if (*pval != NULL) {
                ASN1_item_ex_free(pval, it);
                *pval = NULL;
        }

        /* If no IMPLICIT tagging use UNIVERSAL/SEQUENCE. */
        if (tag_number == -1) {
                tag_class = V_ASN1_UNIVERSAL;
                tag_number = V_ASN1_SEQUENCE;
        }

        /* Read ASN.1 SEQUENCE header. */
        ret = asn1_check_tag(&cbs_seq, &length, NULL, NULL, &indefinite,
            &constructed, tag_number, tag_class, optional);
        if (ret == -1)
                return -1;
        if (ret != 1) {
                ASN1error(ERR_R_NESTED_ASN1_ERROR);
                goto err;
        }

        if (!constructed) {
                ASN1error(ASN1_R_SEQUENCE_NOT_CONSTRUCTED);
                goto err;
        }

        if (indefinite) {
                eoc_needed = 1;
                CBS_init(&cbs_seq_content, CBS_data(&cbs_seq), CBS_len(&cbs_seq));
        } else {
                eoc_needed = 0;
                if (!CBS_get_bytes(&cbs_seq, &cbs_seq_content, length))
                        goto err;
        }

        if (!ASN1_item_ex_new(&aseq, it)) {
                ASN1error(ERR_R_NESTED_ASN1_ERROR);
                goto err;
        }

        if (asn1_cb != NULL && !asn1_cb(ASN1_OP_D2I_PRE, &aseq, it, NULL)) {
                ASN1error(ASN1_R_AUX_ERROR);
                goto err;
        }

        for (i = 0; i < it->tcount; i++) {
                at = &it->templates[i];

                if (asn1_check_eoc(&cbs_seq_content)) {
                        if (!indefinite) {
                                ASN1error(ASN1_R_UNEXPECTED_EOC);
                                goto err;
                        }
                        eoc_needed = 0;
                        break;
                }
                if (CBS_len(&cbs_seq_content) == 0)
                        break;

                if ((seqat = asn1_do_adb(&aseq, at, 1)) == NULL)
                        goto err;

                pseqval = asn1_get_field_ptr(&aseq, seqat);

                /*
                 * This was originally implemented to "increase efficiency",
                 * however it currently needs to remain since it papers over
                 * the use of ASN.1 ANY with OPTIONAL in SEQUENCEs (which
                 * asn1_d2i_primitive() currently rejects).
                 */
                optional_field = (seqat->flags & ASN1_TFLG_OPTIONAL) != 0;
                if (i == it->tcount - 1)
                        optional_field = 0;

                ret = asn1_template_d2i(pseqval, &cbs_seq_content,
                    seqat, optional_field, depth);
                if (ret == -1) {
                        /* Absent OPTIONAL component. */
                        ASN1_template_free(pseqval, seqat);
                        continue;
                }
                if (ret != 1) {
                        errat = seqat;
                        goto err;
                }
        }

        if (eoc_needed && !asn1_check_eoc(&cbs_seq_content)) {
                ASN1error(ASN1_R_MISSING_EOC);
                goto err;
        }

        if (indefinite) {
                if (!CBS_skip(&cbs_seq, CBS_offset(&cbs_seq_content)))
                        goto err;
        } else if (CBS_len(&cbs_seq_content) != 0) {
                ASN1error(ASN1_R_SEQUENCE_LENGTH_MISMATCH);
                goto err;
        }

        /*
         * There is no more data in the ASN.1 SEQUENCE, however we may not have
         * populated all fields - check that any remaining are OPTIONAL.
         */
        for (; i < it->tcount; i++) {
                at = &it->templates[i];

                if ((seqat = asn1_do_adb(&aseq, at, 1)) == NULL)
                        goto err;

                if ((seqat->flags & ASN1_TFLG_OPTIONAL) == 0) {
                        ASN1error(ASN1_R_FIELD_MISSING);
                        errat = seqat;
                        goto err;
                }

                /* XXX - this is probably unnecessary with earlier free. */
                pseqval = asn1_get_field_ptr(&aseq, seqat);
                ASN1_template_free(pseqval, seqat);
        }

        if (!CBS_get_bytes(cbs, &cbs_object, CBS_offset(&cbs_seq)))
                goto err;

        if (!asn1_enc_save(&aseq, &cbs_object, it)) {
                ASN1error(ERR_R_MALLOC_FAILURE);
                goto err;
        }

        if (asn1_cb != NULL && !asn1_cb(ASN1_OP_D2I_POST, &aseq, it, NULL)) {
                ASN1error(ASN1_R_AUX_ERROR);
                goto err;
        }

        *pval = aseq;
        aseq = NULL;

        return 1;

 err:
        ASN1_item_ex_free(&aseq, it);

        if (errat != NULL)
                ERR_asprintf_error_data("Field=%s, Type=%s", errat->field_name,
                    it->sname);
        else
                ERR_asprintf_error_data("Type=%s", it->sname);

        return 0;
}

static int
asn1_item_d2i_extern(ASN1_VALUE **pval, CBS *cbs, const ASN1_ITEM *it,
    int tag_number, int tag_class, int optional)
{
        const ASN1_EXTERN_FUNCS *ef = it->funcs;
        const unsigned char *p = NULL;
        ASN1_TLC ctx = { 0 };
        int ret = 0;

        if (CBS_len(cbs) > LONG_MAX)
                return 0;

        p = CBS_data(cbs);

        if ((ret = ef->asn1_ex_d2i(pval, &p, (long)CBS_len(cbs), it,
            tag_number, tag_class, optional, &ctx)) == 1) {
                if (!CBS_skip(cbs, p - CBS_data(cbs)))
                        goto err;
        }
        return ret;

 err:
        ASN1_item_ex_free(pval, it);

        ERR_asprintf_error_data("Type=%s", it->sname);

        return 0;
}

static int
asn1_item_d2i(ASN1_VALUE **pval, CBS *cbs, const ASN1_ITEM *it,
    int tag_number, int tag_class, int optional, int depth)
{
        if (pval == NULL)
                return 0;

        if (++depth > ASN1_MAX_CONSTRUCTED_NEST) {
                ASN1error(ASN1_R_NESTED_TOO_DEEP);
                goto err;
        }

        switch (it->itype) {
        case ASN1_ITYPE_PRIMITIVE:
                if (it->templates != NULL) {
                        /*
                         * Tagging or OPTIONAL is currently illegal on an item
                         * template because the flags can't get passed down.
                         * In practice this isn't a problem: we include the
                         * relevant flags from the item template in the
                         * template itself.
                         */
                        if (tag_number != -1 || optional) {
                                ASN1error(ASN1_R_ILLEGAL_OPTIONS_ON_ITEM_TEMPLATE);
                                goto err;
                        }
                        return asn1_template_d2i(pval, cbs, it->templates,
                            optional, depth);
                }
                return asn1_d2i_primitive(pval, cbs, it, tag_number, tag_class,
                    optional);

        case ASN1_ITYPE_MSTRING:
                return asn1_d2i_mstring(pval, cbs, it, tag_number, tag_class,
                    optional);

        case ASN1_ITYPE_EXTERN:
                return asn1_item_d2i_extern(pval, cbs, it, tag_number,
                    tag_class, optional);

        case ASN1_ITYPE_CHOICE:
                return asn1_item_d2i_choice(pval, cbs, it, tag_number,
                    tag_class, optional, depth);

        case ASN1_ITYPE_NDEF_SEQUENCE:
        case ASN1_ITYPE_SEQUENCE:
                return asn1_item_d2i_sequence(pval, cbs, it, tag_number,
                    tag_class, optional, depth);

        default:
                return 0;
        }

 err:
        ASN1_item_ex_free(pval, it);

        ERR_asprintf_error_data("Type=%s", it->sname);

        return 0;
}

static void
asn1_template_stack_of_free(STACK_OF(ASN1_VALUE) *avals,
    const ASN1_TEMPLATE *at)
{
        ASN1_VALUE *aval;

        if (avals == NULL)
                return;

        while (sk_ASN1_VALUE_num(avals) > 0) {
                aval = sk_ASN1_VALUE_pop(avals);
                ASN1_item_ex_free(&aval, at->item);
        }
        sk_ASN1_VALUE_free(avals);
}

static int
asn1_template_stack_of_d2i(ASN1_VALUE **pval, CBS *cbs, const ASN1_TEMPLATE *at,
    int optional, int depth)
{
        CBS cbs_object, cbs_object_content;
        STACK_OF(ASN1_VALUE) *avals = NULL;
        ASN1_VALUE *aval = NULL;
        int tag_number, tag_class;
        int eoc_needed;
        int indefinite;
        size_t length;
        int ret;

        CBS_init(&cbs_object, CBS_data(cbs), CBS_len(cbs));

        if (pval == NULL)
                return 0;

        asn1_template_stack_of_free((STACK_OF(ASN1_VALUE) *)*pval, at);
        *pval = NULL;

        tag_number = at->tag;
        tag_class = at->flags & ASN1_TFLG_TAG_CLASS;

        /* Determine the inner tag value for SET OF or SEQUENCE OF. */
        if ((at->flags & ASN1_TFLG_IMPTAG) == 0) {
                tag_number = V_ASN1_SEQUENCE;
                tag_class = V_ASN1_UNIVERSAL;
                if ((at->flags & ASN1_TFLG_SET_OF) != 0)
                        tag_number = V_ASN1_SET;
        }

        ret = asn1_check_tag(&cbs_object, &length, NULL, NULL, &indefinite,
            NULL, tag_number, tag_class, optional);
        if (ret == -1)
                return -1;
        if (ret != 1) {
                ASN1error(ERR_R_NESTED_ASN1_ERROR);
                return 0;
        }

        if (indefinite) {
                eoc_needed = 1;
                CBS_init(&cbs_object_content, CBS_data(&cbs_object),
                    CBS_len(&cbs_object));
        } else {
                eoc_needed = 0;
                if (!CBS_get_bytes(&cbs_object, &cbs_object_content,
                    length))
                        goto err;
        }

        if ((avals = sk_ASN1_VALUE_new_null()) == NULL) {
                ASN1error(ERR_R_MALLOC_FAILURE);
                goto err;
        }

        /* Read as many items as possible. */
        while (CBS_len(&cbs_object_content) > 0) {
                if (asn1_check_eoc(&cbs_object_content)) {
                        if (!eoc_needed) {
                                ASN1error(ASN1_R_UNEXPECTED_EOC);
                                goto err;
                        }
                        eoc_needed = 0;
                        break;
                }
                if (!asn1_item_d2i(&aval, &cbs_object_content, at->item, -1, 0,
                    0, depth)) {
                        ASN1error(ERR_R_NESTED_ASN1_ERROR);
                        goto err;
                }
                if (!sk_ASN1_VALUE_push(avals, aval)) {
                        ASN1error(ERR_R_MALLOC_FAILURE);
                        goto err;
                }
                aval = NULL;
        }
        if (eoc_needed) {
                ASN1error(ASN1_R_MISSING_EOC);
                goto err;
        }

        if (indefinite) {
                if (!CBS_skip(&cbs_object, CBS_offset(&cbs_object_content)))
                        goto err;
        }

        if (!CBS_skip(cbs, CBS_offset(&cbs_object)))
                goto err;

        *pval = (ASN1_VALUE *)avals;
        avals = NULL;

        return 1;

 err:
        asn1_template_stack_of_free(avals, at);
        ASN1_item_ex_free(&aval, at->item);

        return 0;
}

static int
asn1_template_noexp_d2i(ASN1_VALUE **pval, CBS *cbs, const ASN1_TEMPLATE *at,
    int optional, int depth)
{
        int tag_number, tag_class;
        int ret;

        if (pval == NULL)
                return 0;

        if ((at->flags & ASN1_TFLG_SK_MASK) != 0)
                return asn1_template_stack_of_d2i(pval, cbs, at, optional, depth);

        tag_number = -1;
        tag_class = V_ASN1_UNIVERSAL;

        /* See if we need to use IMPLICIT tagging. */
        if ((at->flags & ASN1_TFLG_IMPTAG) != 0) {
                tag_number = at->tag;
                tag_class = at->flags & ASN1_TFLG_TAG_CLASS;
        }

        ret = asn1_item_d2i(pval, cbs, at->item, tag_number, tag_class,
            optional, depth);
        if (ret == -1)
                return -1;
        if (ret != 1) {
                ASN1error(ERR_R_NESTED_ASN1_ERROR);
                goto err;
        }

        return 1;

 err:
        /* XXX - The called function should have freed already. */
        ASN1_template_free(pval, at);
        return 0;
}

static int
asn1_template_d2i(ASN1_VALUE **pval, CBS *cbs, const ASN1_TEMPLATE *at,
    int optional, int depth)
{
        CBS cbs_exp, cbs_exp_content;
        int constructed, indefinite;
        size_t length;
        int ret;

        if (pval == NULL)
                return 0;

        /* Check if EXPLICIT tag is expected. */
        if ((at->flags & ASN1_TFLG_EXPTAG) == 0)
                return asn1_template_noexp_d2i(pval, cbs, at, optional, depth);

        CBS_init(&cbs_exp, CBS_data(cbs), CBS_len(cbs));

        /* Read ASN.1 header for EXPLICIT tagged object. */
        ret = asn1_check_tag(&cbs_exp, &length, NULL, NULL, &indefinite,
            &constructed, at->tag, at->flags & ASN1_TFLG_TAG_CLASS, optional);
        if (ret == -1)
                return -1;
        if (ret != 1) {
                ASN1error(ERR_R_NESTED_ASN1_ERROR);
                return 0;
        }

        if (!constructed) {
                ASN1error(ASN1_R_EXPLICIT_TAG_NOT_CONSTRUCTED);
                return 0;
        }

        if (indefinite) {
                CBS_init(&cbs_exp_content, CBS_data(&cbs_exp), CBS_len(&cbs_exp));
        } else {
                if (!CBS_get_bytes(&cbs_exp, &cbs_exp_content, length))
                        goto err;
        }

        if ((ret = asn1_template_noexp_d2i(pval, &cbs_exp_content, at, 0,
            depth)) != 1) {
                ASN1error(ERR_R_NESTED_ASN1_ERROR);
                return 0;
        }

        if (indefinite) {
                if (!asn1_check_eoc(&cbs_exp_content)) {
                        ASN1error(ASN1_R_MISSING_EOC);
                        goto err;
                }
                if (!CBS_skip(&cbs_exp, CBS_offset(&cbs_exp_content)))
                        goto err;
        } else if (CBS_len(&cbs_exp_content) != 0) {
                ASN1error(ASN1_R_SEQUENCE_LENGTH_MISMATCH);
                goto err;
        }

        if (!CBS_skip(cbs, CBS_offset(&cbs_exp)))
                goto err;

        return 1;

 err:
        ASN1_template_free(pval, at);
        return 0;
}

ASN1_VALUE *
ASN1_item_d2i(ASN1_VALUE **pval, const unsigned char **in, long inlen,
    const ASN1_ITEM *it)
{
        ASN1_VALUE *ptmpval = NULL;

        if (pval == NULL)
                pval = &ptmpval;
        if (ASN1_item_ex_d2i(pval, in, inlen, it, -1, 0, 0, NULL) <= 0)
                return NULL;

        return *pval;
}
LCRYPTO_ALIAS(ASN1_item_d2i);

int
ASN1_item_ex_d2i(ASN1_VALUE **pval, const unsigned char **in, long inlen,
    const ASN1_ITEM *it, int tag_number, int tag_class, char optional,
    ASN1_TLC *ctx)
{
        CBS cbs;
        int ret;

        if (inlen < 0)
                return 0;

        CBS_init(&cbs, *in, inlen);
        if ((ret = asn1_item_d2i(pval, &cbs, it, tag_number, tag_class,
            (int)optional, 0)) == 1)
                *in = CBS_data(&cbs);

        return ret;
}
LCRYPTO_ALIAS(ASN1_item_ex_d2i);