crypto/asn1/tasn_enc.c - boringssl - Git at Google

 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
  * This package is an SSL implementation written
  * by Eric Young (eay@cryptsoft.com).
  * The implementation was written so as to conform with Netscapes SSL.
  *
  * This library is free for commercial and non-commercial use as long as
  * the following conditions are aheared to.  The following conditions
  * apply to all code found in this distribution, be it the RC4, RSA,
  * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
  * included with this distribution is covered by the same copyright terms
  * except that the holder is Tim Hudson (tjh@cryptsoft.com).
  *
  * Copyright remains Eric Young's, and as such any Copyright notices in
  * the code are not to be removed.
  * If this package is used in a product, Eric Young should be given attribution
  * as the author of the parts of the library used.
  * This can be in the form of a textual message at program startup or
  * in documentation (online or textual) provided with the package.
  *
  * 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 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 acknowledgement:
  *    "This product includes cryptographic software written by
  *     Eric Young (eay@cryptsoft.com)"
  *    The word 'cryptographic' can be left out if the rouines from the library
  *    being used are not cryptographic related :-).
  * 4. If you include any Windows specific code (or a derivative thereof) from
  *    the apps directory (application code) you must include an acknowledgement:
  *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
  *
  * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
  * ANY EXPRESS 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 AUTHOR OR 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.
  *
  * The licence and distribution terms for any publically available version or
  * derivative of this code cannot be changed.  i.e. this code cannot simply be
  * copied and put under another distribution licence
  * [including the GNU Public Licence.] */

 #include <openssl/asn1.h>

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

 #include <openssl/asn1t.h>
 #include <openssl/mem.h>

 #include "../internal.h"
 #include "internal.h"


 static int asn1_item_ex_i2d_opt(ASN1_VALUE **pval, unsigned char **out,
                                 const ASN1_ITEM *it, int tag, int aclass,
                                 int optional);
 static int asn1_i2d_ex_primitive(ASN1_VALUE **pval, unsigned char **out,
                                  const ASN1_ITEM *it, int tag, int aclass,
                                  int optional);
 static int asn1_ex_i2c(ASN1_VALUE **pval, unsigned char *cont, int *out_omit,
                        int *putype, const ASN1_ITEM *it);
 static int asn1_set_seq_out(STACK_OF(ASN1_VALUE) *sk, unsigned char **out,
                             int skcontlen, const ASN1_ITEM *item, int do_sort);
 static int asn1_template_ex_i2d(ASN1_VALUE **pval, unsigned char **out,
                                 const ASN1_TEMPLATE *tt, int tag, int aclass);

 // Top level i2d equivalents

 int ASN1_item_i2d(ASN1_VALUE *val, unsigned char **out, const ASN1_ITEM *it) {
   if (out && !*out) {
     unsigned char *p, *buf;
     int len = ASN1_item_ex_i2d(&val, NULL, it, /*tag=*/-1, /*aclass=*/0);
     if (len <= 0) {
       return len;
     }
     buf = OPENSSL_malloc(len);
     if (!buf) {
       OPENSSL_PUT_ERROR(ASN1, ERR_R_MALLOC_FAILURE);
       return -1;
     }
     p = buf;
     int len2 = ASN1_item_ex_i2d(&val, &p, it, /*tag=*/-1, /*aclass=*/0);
     if (len2 <= 0) {
       return len2;
     }
     assert(len == len2);
     *out = buf;
     return len;
   }

   return ASN1_item_ex_i2d(&val, out, it, /*tag=*/-1, /*aclass=*/0);
 }

 // Encode an item, taking care of IMPLICIT tagging (if any). This function
 // performs the normal item handling: it can be used in external types.

 int ASN1_item_ex_i2d(ASN1_VALUE **pval, unsigned char **out,
                      const ASN1_ITEM *it, int tag, int aclass) {
   int ret = asn1_item_ex_i2d_opt(pval, out, it, tag, aclass, /*optional=*/0);
   assert(ret != 0);
   return ret;
 }

 // asn1_item_ex_i2d_opt behaves like |ASN1_item_ex_i2d| but, if |optional| is
 // non-zero and |*pval| is omitted, it returns zero and writes no bytes.
 int asn1_item_ex_i2d_opt(ASN1_VALUE **pval, unsigned char **out,
                          const ASN1_ITEM *it, int tag, int aclass,
                          int optional) {
   const ASN1_TEMPLATE *tt = NULL;
   int i, seqcontlen, seqlen;

   // Historically, |aclass| was repurposed to pass additional flags into the
   // encoding process.
   assert((aclass & ASN1_TFLG_TAG_CLASS) == aclass);
   // If not overridding the tag, |aclass| is ignored and should be zero.
   assert(tag != -1 || aclass == 0);

   // All fields are pointers, except for boolean |ASN1_ITYPE_PRIMITIVE|s.
   // Optional primitives are handled later.
   if ((it->itype != ASN1_ITYPE_PRIMITIVE) && !*pval) {
     if (optional) {
       return 0;
     }
     OPENSSL_PUT_ERROR(ASN1, ASN1_R_MISSING_VALUE);
     return -1;
   }

   switch (it->itype) {
     case ASN1_ITYPE_PRIMITIVE:
       if (it->templates) {
         if (it->templates->flags & ASN1_TFLG_OPTIONAL) {
           OPENSSL_PUT_ERROR(ASN1, ASN1_R_BAD_TEMPLATE);
           return -1;
         }
         return asn1_template_ex_i2d(pval, out, it->templates, tag, aclass);
       }
       return asn1_i2d_ex_primitive(pval, out, it, tag, aclass, optional);

     case ASN1_ITYPE_MSTRING:
       // It never makes sense for multi-strings to have implicit tagging, so
       // if tag != -1, then this looks like an error in the template.
       if (tag != -1) {
         OPENSSL_PUT_ERROR(ASN1, ASN1_R_BAD_TEMPLATE);
         return -1;
       }
       return asn1_i2d_ex_primitive(pval, out, it, -1, 0, optional);

     case ASN1_ITYPE_CHOICE: {
       // It never makes sense for CHOICE types to have implicit tagging, so if
       // tag != -1, then this looks like an error in the template.
       if (tag != -1) {
         OPENSSL_PUT_ERROR(ASN1, ASN1_R_BAD_TEMPLATE);
         return -1;
       }
       i = asn1_get_choice_selector(pval, it);
       if (i < 0 || i >= it->tcount) {
         OPENSSL_PUT_ERROR(ASN1, ASN1_R_NO_MATCHING_CHOICE_TYPE);
         return -1;
       }
       const ASN1_TEMPLATE *chtt = it->templates + i;
       if (chtt->flags & ASN1_TFLG_OPTIONAL) {
         OPENSSL_PUT_ERROR(ASN1, ASN1_R_BAD_TEMPLATE);
         return -1;
       }
       ASN1_VALUE **pchval = asn1_get_field_ptr(pval, chtt);
       return asn1_template_ex_i2d(pchval, out, chtt, -1, 0);
     }

     case ASN1_ITYPE_EXTERN: {
       // If new style i2d it does all the work
       const ASN1_EXTERN_FUNCS *ef = it->funcs;
       int ret = ef->asn1_ex_i2d(pval, out, it, tag, aclass);
       if (ret == 0) {
         // |asn1_ex_i2d| should never return zero. We have already checked
         // for optional values generically, and |ASN1_ITYPE_EXTERN| fields
         // must be pointers.
         OPENSSL_PUT_ERROR(ASN1, ERR_R_INTERNAL_ERROR);
         return -1;
       }
       return ret;
     }

     case ASN1_ITYPE_SEQUENCE: {
       i = asn1_enc_restore(&seqcontlen, out, pval, it);
       // An error occurred
       if (i < 0) {
         return -1;
       }
       // We have a valid cached encoding...
       if (i > 0) {
         return seqcontlen;
       }
       // Otherwise carry on
       seqcontlen = 0;
       // If no IMPLICIT tagging set to SEQUENCE, UNIVERSAL
       if (tag == -1) {
         tag = V_ASN1_SEQUENCE;
         aclass = V_ASN1_UNIVERSAL;
       }
       // First work out sequence content length
       for (i = 0, tt = it->templates; i < it->tcount; tt++, i++) {
         const ASN1_TEMPLATE *seqtt;
         ASN1_VALUE **pseqval;
         int tmplen;
         seqtt = asn1_do_adb(pval, tt, 1);
         if (!seqtt) {
           return -1;
         }
         pseqval = asn1_get_field_ptr(pval, seqtt);
         tmplen = asn1_template_ex_i2d(pseqval, NULL, seqtt, -1, 0);
         if (tmplen == -1 || (tmplen > INT_MAX - seqcontlen)) {
           return -1;
         }
         seqcontlen += tmplen;
       }

       seqlen = ASN1_object_size(/*constructed=*/1, seqcontlen, tag);
       if (!out || seqlen == -1) {
         return seqlen;
       }
       // Output SEQUENCE header
       ASN1_put_object(out, /*constructed=*/1, seqcontlen, tag, aclass);
       for (i = 0, tt = it->templates; i < it->tcount; tt++, i++) {
         const ASN1_TEMPLATE *seqtt;
         ASN1_VALUE **pseqval;
         seqtt = asn1_do_adb(pval, tt, 1);
         if (!seqtt) {
           return -1;
         }
         pseqval = asn1_get_field_ptr(pval, seqtt);
         if (asn1_template_ex_i2d(pseqval, out, seqtt, -1, 0) < 0) {
           return -1;
         }
       }
       return seqlen;
     }

     default:
       OPENSSL_PUT_ERROR(ASN1, ASN1_R_BAD_TEMPLATE);
       return -1;
   }
 }

 // asn1_template_ex_i2d behaves like |asn1_item_ex_i2d_opt| but uses an
 // |ASN1_TEMPLATE| instead of an |ASN1_ITEM|. An |ASN1_TEMPLATE| wraps an
 // |ASN1_ITEM| with modifiers such as tagging, SEQUENCE or SET, etc. Instead of
 // taking an |optional| parameter, it uses the |ASN1_TFLG_OPTIONAL| flag.
 static int asn1_template_ex_i2d(ASN1_VALUE **pval, unsigned char **out,
                                 const ASN1_TEMPLATE *tt, int tag, int iclass) {
   int i, ret, ttag, tclass;
   size_t j;
   uint32_t flags = tt->flags;

   // Historically, |iclass| was repurposed to pass additional flags into the
   // encoding process.
   assert((iclass & ASN1_TFLG_TAG_CLASS) == iclass);
   // If not overridding the tag, |iclass| is ignored and should be zero.
   assert(tag != -1 || iclass == 0);

   // Work out tag and class to use: tagging may come either from the
   // template or the arguments, not both because this would create
   // ambiguity.
   if (flags & ASN1_TFLG_TAG_MASK) {
     // Error if argument and template tagging
     if (tag != -1) {
       OPENSSL_PUT_ERROR(ASN1, ASN1_R_BAD_TEMPLATE);
       return -1;
     }
     // Get tagging from template
     ttag = tt->tag;
     tclass = flags & ASN1_TFLG_TAG_CLASS;
   } else if (tag != -1) {
     // No template tagging, get from arguments
     ttag = tag;
     tclass = iclass & ASN1_TFLG_TAG_CLASS;
   } else {
     ttag = -1;
     tclass = 0;
   }

   const int optional = (flags & ASN1_TFLG_OPTIONAL) != 0;

   // At this point 'ttag' contains the outer tag to use, and 'tclass' is the
   // class.

   if (flags & ASN1_TFLG_SK_MASK) {
     // SET OF, SEQUENCE OF
     STACK_OF(ASN1_VALUE) *sk = (STACK_OF(ASN1_VALUE) *)*pval;
     int isset, sktag, skaclass;
     int skcontlen, sklen;
     ASN1_VALUE *skitem;

     if (!*pval) {
       if (optional) {
         return 0;
       }
       OPENSSL_PUT_ERROR(ASN1, ASN1_R_MISSING_VALUE);
       return -1;
     }

     if (flags & ASN1_TFLG_SET_OF) {
       isset = 1;
       // Historically, types with both bits set were mutated when
       // serialized to apply the sort. We no longer support this.
       assert((flags & ASN1_TFLG_SEQUENCE_OF) == 0);
     } else {
       isset = 0;
     }

     // Work out inner tag value: if EXPLICIT or no tagging use underlying
     // type.
     if ((ttag != -1) && !(flags & ASN1_TFLG_EXPTAG)) {
       sktag = ttag;
       skaclass = tclass;
     } else {
       skaclass = V_ASN1_UNIVERSAL;
       if (isset) {
         sktag = V_ASN1_SET;
       } else {
         sktag = V_ASN1_SEQUENCE;
       }
     }

     // Determine total length of items
     skcontlen = 0;
     for (j = 0; j < sk_ASN1_VALUE_num(sk); j++) {
       int tmplen;
       skitem = sk_ASN1_VALUE_value(sk, j);
       tmplen = ASN1_item_ex_i2d(&skitem, NULL, ASN1_ITEM_ptr(tt->item), -1, 0);
       if (tmplen == -1 || (skcontlen > INT_MAX - tmplen)) {
         return -1;
       }
       skcontlen += tmplen;
     }
     sklen = ASN1_object_size(/*constructed=*/1, skcontlen, sktag);
     if (sklen == -1) {
       return -1;
     }
     // If EXPLICIT need length of surrounding tag
     if (flags & ASN1_TFLG_EXPTAG) {
       ret = ASN1_object_size(/*constructed=*/1, sklen, ttag);
     } else {
       ret = sklen;
     }

     if (!out || ret == -1) {
       return ret;
     }

     // Now encode this lot...
     // EXPLICIT tag
     if (flags & ASN1_TFLG_EXPTAG) {
       ASN1_put_object(out, /*constructed=*/1, sklen, ttag, tclass);
     }
     // SET or SEQUENCE and IMPLICIT tag
     ASN1_put_object(out, /*constructed=*/1, skcontlen, sktag, skaclass);
     // And the stuff itself
     if (!asn1_set_seq_out(sk, out, skcontlen, ASN1_ITEM_ptr(tt->item), isset)) {
       return -1;
     }
     return ret;
   }

   if (flags & ASN1_TFLG_EXPTAG) {
     // EXPLICIT tagging
     // Find length of tagged item
     i = asn1_item_ex_i2d_opt(pval, NULL, ASN1_ITEM_ptr(tt->item), -1, 0,
                              optional);
     if (i <= 0) {
       return i;
     }
     // Find length of EXPLICIT tag
     ret = ASN1_object_size(/*constructed=*/1, i, ttag);
     if (out && ret != -1) {
       // Output tag and item
       ASN1_put_object(out, /*constructed=*/1, i, ttag, tclass);
       if (ASN1_item_ex_i2d(pval, out, ASN1_ITEM_ptr(tt->item), -1, 0) < 0) {
         return -1;
       }
     }
     return ret;
   }

   // Either normal or IMPLICIT tagging
   return asn1_item_ex_i2d_opt(pval, out, ASN1_ITEM_ptr(tt->item), ttag, tclass,
                               optional);
 }

 // Temporary structure used to hold DER encoding of items for SET OF

 typedef struct {
   unsigned char *data;
   int length;
 } DER_ENC;

 static int der_cmp(const void *a, const void *b) {
   const DER_ENC *d1 = a, *d2 = b;
   int cmplen, i;
   cmplen = (d1->length < d2->length) ? d1->length : d2->length;
   i = OPENSSL_memcmp(d1->data, d2->data, cmplen);
   if (i) {
     return i;
   }
   return d1->length - d2->length;
 }

 // asn1_set_seq_out writes |sk| to |out| under the i2d output convention,
 // excluding the tag and length. It returns one on success and zero on error.
 // |skcontlen| must be the total encoded size. If |do_sort| is non-zero, the
 // elements are sorted for a SET OF type. Each element of |sk| has type
 // |item|.
 static int asn1_set_seq_out(STACK_OF(ASN1_VALUE) *sk, unsigned char **out,
                             int skcontlen, const ASN1_ITEM *item, int do_sort) {
   // No need to sort if there are fewer than two items.
   if (!do_sort || sk_ASN1_VALUE_num(sk) < 2) {
     for (size_t i = 0; i < sk_ASN1_VALUE_num(sk); i++) {
       ASN1_VALUE *skitem = sk_ASN1_VALUE_value(sk, i);
       if (ASN1_item_ex_i2d(&skitem, out, item, -1, 0) < 0) {
         return 0;
       }
     }
     return 1;
   }

   if (sk_ASN1_VALUE_num(sk) > ((size_t)-1) / sizeof(DER_ENC)) {
     OPENSSL_PUT_ERROR(ASN1, ERR_R_OVERFLOW);
     return 0;
   }

   int ret = 0;
   unsigned char *const buf = OPENSSL_malloc(skcontlen);
   DER_ENC *encoded = OPENSSL_malloc(sk_ASN1_VALUE_num(sk) * sizeof(*encoded));
   if (encoded == NULL || buf == NULL) {
     OPENSSL_PUT_ERROR(ASN1, ERR_R_MALLOC_FAILURE);
     goto err;
   }

   // Encode all the elements into |buf| and populate |encoded|.
   unsigned char *p = buf;
   for (size_t i = 0; i < sk_ASN1_VALUE_num(sk); i++) {
     ASN1_VALUE *skitem = sk_ASN1_VALUE_value(sk, i);
     encoded[i].data = p;
     encoded[i].length = ASN1_item_ex_i2d(&skitem, &p, item, -1, 0);
     if (encoded[i].length < 0) {
       goto err;
     }
     assert(p - buf <= skcontlen);
   }

   qsort(encoded, sk_ASN1_VALUE_num(sk), sizeof(*encoded), der_cmp);

   // Output the elements in sorted order.
   p = *out;
   for (size_t i = 0; i < sk_ASN1_VALUE_num(sk); i++) {
     OPENSSL_memcpy(p, encoded[i].data, encoded[i].length);
     p += encoded[i].length;
   }
   *out = p;

   ret = 1;

 err:
   OPENSSL_free(encoded);
   OPENSSL_free(buf);
   return ret;
 }

 // asn1_i2d_ex_primitive behaves like |ASN1_item_ex_i2d| but |item| must be a
 // a PRIMITIVE or MSTRING type that is not an |ASN1_ITEM_TEMPLATE|.
 static int asn1_i2d_ex_primitive(ASN1_VALUE **pval, unsigned char **out,
                                  const ASN1_ITEM *it, int tag, int aclass,
                                  int optional) {
   // Get length of content octets and maybe find out the underlying type.
   int omit;
   int utype = it->utype;
   int len = asn1_ex_i2c(pval, NULL, &omit, &utype, it);
   if (len < 0) {
     return -1;
   }
   if (omit) {
     if (optional) {
       return 0;
     }
     OPENSSL_PUT_ERROR(ASN1, ASN1_R_MISSING_VALUE);
     return -1;
   }

   // If SEQUENCE, SET or OTHER then header is included in pseudo content
   // octets so don't include tag+length. We need to check here because the
   // call to asn1_ex_i2c() could change utype.
   int usetag =
       utype != V_ASN1_SEQUENCE && utype != V_ASN1_SET && utype != V_ASN1_OTHER;

   // If not implicitly tagged get tag from underlying type
   if (tag == -1) {
     tag = utype;
   }

   // Output tag+length followed by content octets
   if (out) {
     if (usetag) {
       ASN1_put_object(out, /*constructed=*/0, len, tag, aclass);
     }
     int len2 = asn1_ex_i2c(pval, *out, &omit, &utype, it);
     if (len2 < 0) {
       return -1;
     }
     assert(len == len2);
     assert(!omit);
     *out += len;
   }

   if (usetag) {
     return ASN1_object_size(/*constructed=*/0, len, tag);
   }
   return len;
 }

 // asn1_ex_i2c writes the |*pval| to |cout| under the i2d output convention,
 // excluding the tag and length. It returns the number of bytes written,
 // possibly zero, on success or -1 on error. If |*pval| should be omitted, it
 // returns zero and sets |*out_omit| to true.
 //
 // If |it| is an MSTRING or ANY type, it gets the underlying type from |*pval|,
 // which must be an |ASN1_STRING| or |ASN1_TYPE|, respectively. It then updates
 // |*putype| with the tag number of type used, or |V_ASN1_OTHER| if it was not a
 // universal type. If |*putype| is set to |V_ASN1_SEQUENCE|, |V_ASN1_SET|, or
 // |V_ASN1_OTHER|, it additionally outputs the tag and length, so the caller
 // must not do so.
 //
 // Otherwise, |*putype| must contain |it->utype|.
 //
 // WARNING: Unlike most functions in this file, |asn1_ex_i2c| can return zero
 // without omitting the element. ASN.1 values may have empty contents.
 static int asn1_ex_i2c(ASN1_VALUE **pval, unsigned char *cout, int *out_omit,
                        int *putype, const ASN1_ITEM *it) {
   ASN1_BOOLEAN *tbool = NULL;
   ASN1_STRING *strtmp;
   ASN1_OBJECT *otmp;
   int utype;
   const unsigned char *cont;
   unsigned char c;
   int len;

   // Historically, |it->funcs| for primitive types contained an
   // |ASN1_PRIMITIVE_FUNCS| table of callbacks.
   assert(it->funcs == NULL);

   *out_omit = 0;

   // Should type be omitted?
   if ((it->itype != ASN1_ITYPE_PRIMITIVE) || (it->utype != V_ASN1_BOOLEAN)) {
     if (!*pval) {
       *out_omit = 1;
       return 0;
     }
   }

   if (it->itype == ASN1_ITYPE_MSTRING) {
     // If MSTRING type set the underlying type
     strtmp = (ASN1_STRING *)*pval;
     utype = strtmp->type;
     if (utype < 0 && utype != V_ASN1_OTHER) {
       // MSTRINGs can have type -1 when default-constructed.
       OPENSSL_PUT_ERROR(ASN1, ASN1_R_WRONG_TYPE);
       return -1;
     }
     // Negative INTEGER and ENUMERATED values use |ASN1_STRING| type values
     // that do not match their corresponding utype values. INTEGERs cannot
     // participate in MSTRING types, but ENUMERATEDs can.
     //
     // TODO(davidben): Is this a bug? Although arguably one of the MSTRING
     // types should contain more values, rather than less. See
     // https://crbug.com/boringssl/412. But it is not possible to fit all
     // possible ANY values into an |ASN1_STRING|, so matching the spec here
     // is somewhat hopeless.
     if (utype == V_ASN1_NEG_INTEGER) {
       utype = V_ASN1_INTEGER;
     } else if (utype == V_ASN1_NEG_ENUMERATED) {
       utype = V_ASN1_ENUMERATED;
     }
     *putype = utype;
   } else if (it->utype == V_ASN1_ANY) {
     // If ANY set type and pointer to value
     ASN1_TYPE *typ;
     typ = (ASN1_TYPE *)*pval;
     utype = typ->type;
     if (utype < 0 && utype != V_ASN1_OTHER) {
       // |ASN1_TYPE|s can have type -1 when default-constructed.
       OPENSSL_PUT_ERROR(ASN1, ASN1_R_WRONG_TYPE);
       return -1;
     }
     *putype = utype;
     pval = &typ->value.asn1_value;
   } else {
     utype = *putype;
   }

   switch (utype) {
     case V_ASN1_OBJECT:
       otmp = (ASN1_OBJECT *)*pval;
       cont = otmp->data;
       len = otmp->length;
       if (len == 0) {
         // Some |ASN1_OBJECT|s do not have OIDs and cannot be serialized.
         OPENSSL_PUT_ERROR(ASN1, ASN1_R_ILLEGAL_OBJECT);
         return -1;
       }
       break;

     case V_ASN1_NULL:
       cont = NULL;
       len = 0;
       break;

     case V_ASN1_BOOLEAN:
       tbool = (ASN1_BOOLEAN *)pval;
       if (*tbool == -1) {
         *out_omit = 1;
         return 0;
       }
       if (it->utype != V_ASN1_ANY) {
         // Default handling if value == size field then omit
         if ((*tbool && (it->size > 0)) || (!*tbool && !it->size)) {
           *out_omit = 1;
           return 0;
         }
       }
       c = *tbool ? 0xff : 0x00;
       cont = &c;
       len = 1;
       break;

     case V_ASN1_BIT_STRING: {
       int ret =
           i2c_ASN1_BIT_STRING((ASN1_BIT_STRING *)*pval, cout ? &cout : NULL);
       // |i2c_ASN1_BIT_STRING| returns zero on error instead of -1.
       return ret <= 0 ? -1 : ret;
     }

     case V_ASN1_INTEGER:
     case V_ASN1_ENUMERATED: {
       // |i2c_ASN1_INTEGER| also handles ENUMERATED.
       int ret = i2c_ASN1_INTEGER((ASN1_INTEGER *)*pval, cout ? &cout : NULL);
       // |i2c_ASN1_INTEGER| returns zero on error instead of -1.
       return ret <= 0 ? -1 : ret;
     }

     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_SEQUENCE:
     case V_ASN1_SET:
     default:
       // All based on ASN1_STRING and handled the same
       strtmp = (ASN1_STRING *)*pval;
       cont = strtmp->data;
       len = strtmp->length;

       break;
   }
   if (cout && len) {
     OPENSSL_memcpy(cout, cont, len);
   }
   return len;
 }
	/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
	* All rights reserved.
	*
	* This package is an SSL implementation written
	* by Eric Young (eay@cryptsoft.com).
	* The implementation was written so as to conform with Netscapes SSL.
	*
	* This library is free for commercial and non-commercial use as long as
	* the following conditions are aheared to. The following conditions
	* apply to all code found in this distribution, be it the RC4, RSA,
	* lhash, DES, etc., code; not just the SSL code. The SSL documentation
	* included with this distribution is covered by the same copyright terms
	* except that the holder is Tim Hudson (tjh@cryptsoft.com).
	*
	* Copyright remains Eric Young's, and as such any Copyright notices in
	* the code are not to be removed.
	* If this package is used in a product, Eric Young should be given attribution
	* as the author of the parts of the library used.
	* This can be in the form of a textual message at program startup or
	* in documentation (online or textual) provided with the package.
	*
	* 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 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 acknowledgement:
	* "This product includes cryptographic software written by
	* Eric Young (eay@cryptsoft.com)"
	* The word 'cryptographic' can be left out if the rouines from the library
	* being used are not cryptographic related :-).
	* 4. If you include any Windows specific code (or a derivative thereof) from
	* the apps directory (application code) you must include an acknowledgement:
	* "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
	*
	* THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
	* ANY EXPRESS 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 AUTHOR OR 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.
	*
	* The licence and distribution terms for any publically available version or
	* derivative of this code cannot be changed. i.e. this code cannot simply be
	* copied and put under another distribution licence
	* [including the GNU Public Licence.] */

	#include <openssl/asn1.h>

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

	#include <openssl/asn1t.h>
	#include <openssl/mem.h>

	#include "../internal.h"
	#include "internal.h"


	static int asn1_item_ex_i2d_opt(ASN1_VALUE pval, unsigned char out,
	const ASN1_ITEM *it, int tag, int aclass,
	int optional);
	static int asn1_i2d_ex_primitive(ASN1_VALUE pval, unsigned char out,
	const ASN1_ITEM *it, int tag, int aclass,
	int optional);
	static int asn1_ex_i2c(ASN1_VALUE *pval, unsigned char cont, int *out_omit,
	int putype, const ASN1_ITEM it);
	static int asn1_set_seq_out(STACK_OF(ASN1_VALUE) sk, unsigned char *out,
	int skcontlen, const ASN1_ITEM *item, int do_sort);
	static int asn1_template_ex_i2d(ASN1_VALUE pval, unsigned char out,
	const ASN1_TEMPLATE *tt, int tag, int aclass);

	// Top level i2d equivalents

	int ASN1_item_i2d(ASN1_VALUE val, unsigned char out, const ASN1_ITEM it) {
	if (out && !*out) {
	unsigned char p, buf;
	int len = ASN1_item_ex_i2d(&val, NULL, it, /tag=/-1, /aclass=/0);
	if (len <= 0) {
	return len;
	}
	buf = OPENSSL_malloc(len);
	if (!buf) {
	OPENSSL_PUT_ERROR(ASN1, ERR_R_MALLOC_FAILURE);
	return -1;
	}
	p = buf;
	int len2 = ASN1_item_ex_i2d(&val, &p, it, /tag=/-1, /aclass=/0);
	if (len2 <= 0) {
	return len2;
	}
	assert(len == len2);
	*out = buf;
	return len;
	}

	return ASN1_item_ex_i2d(&val, out, it, /tag=/-1, /aclass=/0);
	}

	// Encode an item, taking care of IMPLICIT tagging (if any). This function
	// performs the normal item handling: it can be used in external types.

	int ASN1_item_ex_i2d(ASN1_VALUE pval, unsigned char out,
	const ASN1_ITEM *it, int tag, int aclass) {
	int ret = asn1_item_ex_i2d_opt(pval, out, it, tag, aclass, /optional=/0);
	assert(ret != 0);
	return ret;
	}

	// asn1_item_ex_i2d_opt behaves like \|ASN1_item_ex_i2d\| but, if \|optional\| is
	// non-zero and \|*pval\| is omitted, it returns zero and writes no bytes.
	int asn1_item_ex_i2d_opt(ASN1_VALUE pval, unsigned char out,
	const ASN1_ITEM *it, int tag, int aclass,
	int optional) {
	const ASN1_TEMPLATE *tt = NULL;
	int i, seqcontlen, seqlen;

	// Historically, \|aclass\| was repurposed to pass additional flags into the
	// encoding process.
	assert((aclass & ASN1_TFLG_TAG_CLASS) == aclass);
	// If not overridding the tag, \|aclass\| is ignored and should be zero.
	assert(tag != -1 \|\| aclass == 0);

	// All fields are pointers, except for boolean \|ASN1_ITYPE_PRIMITIVE\|s.
	// Optional primitives are handled later.
	if ((it->itype != ASN1_ITYPE_PRIMITIVE) && !*pval) {
	if (optional) {
	return 0;
	}
	OPENSSL_PUT_ERROR(ASN1, ASN1_R_MISSING_VALUE);
	return -1;
	}

	switch (it->itype) {
	case ASN1_ITYPE_PRIMITIVE:
	if (it->templates) {
	if (it->templates->flags & ASN1_TFLG_OPTIONAL) {
	OPENSSL_PUT_ERROR(ASN1, ASN1_R_BAD_TEMPLATE);
	return -1;
	}
	return asn1_template_ex_i2d(pval, out, it->templates, tag, aclass);
	}
	return asn1_i2d_ex_primitive(pval, out, it, tag, aclass, optional);

	case ASN1_ITYPE_MSTRING:
	// It never makes sense for multi-strings to have implicit tagging, so
	// if tag != -1, then this looks like an error in the template.
	if (tag != -1) {
	OPENSSL_PUT_ERROR(ASN1, ASN1_R_BAD_TEMPLATE);
	return -1;
	}
	return asn1_i2d_ex_primitive(pval, out, it, -1, 0, optional);

	case ASN1_ITYPE_CHOICE: {
	// It never makes sense for CHOICE types to have implicit tagging, so if
	// tag != -1, then this looks like an error in the template.
	if (tag != -1) {
	OPENSSL_PUT_ERROR(ASN1, ASN1_R_BAD_TEMPLATE);
	return -1;
	}
	i = asn1_get_choice_selector(pval, it);
	if (i < 0 \|\| i >= it->tcount) {
	OPENSSL_PUT_ERROR(ASN1, ASN1_R_NO_MATCHING_CHOICE_TYPE);
	return -1;
	}
	const ASN1_TEMPLATE *chtt = it->templates + i;
	if (chtt->flags & ASN1_TFLG_OPTIONAL) {
	OPENSSL_PUT_ERROR(ASN1, ASN1_R_BAD_TEMPLATE);
	return -1;
	}
	ASN1_VALUE **pchval = asn1_get_field_ptr(pval, chtt);
	return asn1_template_ex_i2d(pchval, out, chtt, -1, 0);
	}

	case ASN1_ITYPE_EXTERN: {
	// If new style i2d it does all the work
	const ASN1_EXTERN_FUNCS *ef = it->funcs;
	int ret = ef->asn1_ex_i2d(pval, out, it, tag, aclass);
	if (ret == 0) {
	// \|asn1_ex_i2d\| should never return zero. We have already checked
	// for optional values generically, and \|ASN1_ITYPE_EXTERN\| fields
	// must be pointers.
	OPENSSL_PUT_ERROR(ASN1, ERR_R_INTERNAL_ERROR);
	return -1;
	}
	return ret;
	}

	case ASN1_ITYPE_SEQUENCE: {
	i = asn1_enc_restore(&seqcontlen, out, pval, it);
	// An error occurred
	if (i < 0) {
	return -1;
	}
	// We have a valid cached encoding...
	if (i > 0) {
	return seqcontlen;
	}
	// Otherwise carry on
	seqcontlen = 0;
	// If no IMPLICIT tagging set to SEQUENCE, UNIVERSAL
	if (tag == -1) {
	tag = V_ASN1_SEQUENCE;
	aclass = V_ASN1_UNIVERSAL;
	}
	// First work out sequence content length
	for (i = 0, tt = it->templates; i < it->tcount; tt++, i++) {
	const ASN1_TEMPLATE *seqtt;
	ASN1_VALUE **pseqval;
	int tmplen;
	seqtt = asn1_do_adb(pval, tt, 1);
	if (!seqtt) {
	return -1;
	}
	pseqval = asn1_get_field_ptr(pval, seqtt);
	tmplen = asn1_template_ex_i2d(pseqval, NULL, seqtt, -1, 0);
	if (tmplen == -1 \|\| (tmplen > INT_MAX - seqcontlen)) {
	return -1;
	}
	seqcontlen += tmplen;
	}

	seqlen = ASN1_object_size(/constructed=/1, seqcontlen, tag);
	if (!out \|\| seqlen == -1) {
	return seqlen;
	}
	// Output SEQUENCE header
	ASN1_put_object(out, /constructed=/1, seqcontlen, tag, aclass);
	for (i = 0, tt = it->templates; i < it->tcount; tt++, i++) {
	const ASN1_TEMPLATE *seqtt;
	ASN1_VALUE **pseqval;
	seqtt = asn1_do_adb(pval, tt, 1);
	if (!seqtt) {
	return -1;
	}
	pseqval = asn1_get_field_ptr(pval, seqtt);
	if (asn1_template_ex_i2d(pseqval, out, seqtt, -1, 0) < 0) {
	return -1;
	}
	}
	return seqlen;
	}

	default:
	OPENSSL_PUT_ERROR(ASN1, ASN1_R_BAD_TEMPLATE);
	return -1;
	}
	}

	// asn1_template_ex_i2d behaves like \|asn1_item_ex_i2d_opt\| but uses an
	// \|ASN1_TEMPLATE\| instead of an \|ASN1_ITEM\|. An \|ASN1_TEMPLATE\| wraps an
	// \|ASN1_ITEM\| with modifiers such as tagging, SEQUENCE or SET, etc. Instead of
	// taking an \|optional\| parameter, it uses the \|ASN1_TFLG_OPTIONAL\| flag.
	static int asn1_template_ex_i2d(ASN1_VALUE pval, unsigned char out,
	const ASN1_TEMPLATE *tt, int tag, int iclass) {
	int i, ret, ttag, tclass;
	size_t j;
	uint32_t flags = tt->flags;

	// Historically, \|iclass\| was repurposed to pass additional flags into the
	// encoding process.
	assert((iclass & ASN1_TFLG_TAG_CLASS) == iclass);
	// If not overridding the tag, \|iclass\| is ignored and should be zero.
	assert(tag != -1 \|\| iclass == 0);

	// Work out tag and class to use: tagging may come either from the
	// template or the arguments, not both because this would create
	// ambiguity.
	if (flags & ASN1_TFLG_TAG_MASK) {
	// Error if argument and template tagging
	if (tag != -1) {
	OPENSSL_PUT_ERROR(ASN1, ASN1_R_BAD_TEMPLATE);
	return -1;
	}
	// Get tagging from template
	ttag = tt->tag;
	tclass = flags & ASN1_TFLG_TAG_CLASS;
	} else if (tag != -1) {
	// No template tagging, get from arguments
	ttag = tag;
	tclass = iclass & ASN1_TFLG_TAG_CLASS;
	} else {
	ttag = -1;
	tclass = 0;
	}

	const int optional = (flags & ASN1_TFLG_OPTIONAL) != 0;

	// At this point 'ttag' contains the outer tag to use, and 'tclass' is the
	// class.

	if (flags & ASN1_TFLG_SK_MASK) {
	// SET OF, SEQUENCE OF
	STACK_OF(ASN1_VALUE) sk = (STACK_OF(ASN1_VALUE) )*pval;
	int isset, sktag, skaclass;
	int skcontlen, sklen;
	ASN1_VALUE *skitem;

	if (!*pval) {
	if (optional) {
	return 0;
	}
	OPENSSL_PUT_ERROR(ASN1, ASN1_R_MISSING_VALUE);
	return -1;
	}

	if (flags & ASN1_TFLG_SET_OF) {
	isset = 1;
	// Historically, types with both bits set were mutated when
	// serialized to apply the sort. We no longer support this.
	assert((flags & ASN1_TFLG_SEQUENCE_OF) == 0);
	} else {
	isset = 0;
	}

	// Work out inner tag value: if EXPLICIT or no tagging use underlying
	// type.
	if ((ttag != -1) && !(flags & ASN1_TFLG_EXPTAG)) {
	sktag = ttag;
	skaclass = tclass;
	} else {
	skaclass = V_ASN1_UNIVERSAL;
	if (isset) {
	sktag = V_ASN1_SET;
	} else {
	sktag = V_ASN1_SEQUENCE;
	}
	}

	// Determine total length of items
	skcontlen = 0;
	for (j = 0; j < sk_ASN1_VALUE_num(sk); j++) {
	int tmplen;
	skitem = sk_ASN1_VALUE_value(sk, j);
	tmplen = ASN1_item_ex_i2d(&skitem, NULL, ASN1_ITEM_ptr(tt->item), -1, 0);
	if (tmplen == -1 \|\| (skcontlen > INT_MAX - tmplen)) {
	return -1;
	}
	skcontlen += tmplen;
	}
	sklen = ASN1_object_size(/constructed=/1, skcontlen, sktag);
	if (sklen == -1) {
	return -1;
	}
	// If EXPLICIT need length of surrounding tag
	if (flags & ASN1_TFLG_EXPTAG) {
	ret = ASN1_object_size(/constructed=/1, sklen, ttag);
	} else {
	ret = sklen;
	}

	if (!out \|\| ret == -1) {
	return ret;
	}

	// Now encode this lot...
	// EXPLICIT tag
	if (flags & ASN1_TFLG_EXPTAG) {
	ASN1_put_object(out, /constructed=/1, sklen, ttag, tclass);
	}
	// SET or SEQUENCE and IMPLICIT tag
	ASN1_put_object(out, /constructed=/1, skcontlen, sktag, skaclass);
	// And the stuff itself
	if (!asn1_set_seq_out(sk, out, skcontlen, ASN1_ITEM_ptr(tt->item), isset)) {
	return -1;
	}
	return ret;
	}

	if (flags & ASN1_TFLG_EXPTAG) {
	// EXPLICIT tagging
	// Find length of tagged item
	i = asn1_item_ex_i2d_opt(pval, NULL, ASN1_ITEM_ptr(tt->item), -1, 0,
	optional);
	if (i <= 0) {
	return i;
	}
	// Find length of EXPLICIT tag
	ret = ASN1_object_size(/constructed=/1, i, ttag);
	if (out && ret != -1) {
	// Output tag and item
	ASN1_put_object(out, /constructed=/1, i, ttag, tclass);
	if (ASN1_item_ex_i2d(pval, out, ASN1_ITEM_ptr(tt->item), -1, 0) < 0) {
	return -1;
	}
	}
	return ret;
	}

	// Either normal or IMPLICIT tagging
	return asn1_item_ex_i2d_opt(pval, out, ASN1_ITEM_ptr(tt->item), ttag, tclass,
	optional);
	}

	// Temporary structure used to hold DER encoding of items for SET OF

	typedef struct {
	unsigned char *data;
	int length;
	} DER_ENC;

	static int der_cmp(const void a, const void b) {
	const DER_ENC d1 = a, d2 = b;
	int cmplen, i;
	cmplen = (d1->length < d2->length) ? d1->length : d2->length;
	i = OPENSSL_memcmp(d1->data, d2->data, cmplen);
	if (i) {
	return i;
	}
	return d1->length - d2->length;
	}

	// asn1_set_seq_out writes \|sk\| to \|out\| under the i2d output convention,
	// excluding the tag and length. It returns one on success and zero on error.
	// \|skcontlen\| must be the total encoded size. If \|do_sort\| is non-zero, the
	// elements are sorted for a SET OF type. Each element of \|sk\| has type
	// \|item\|.
	static int asn1_set_seq_out(STACK_OF(ASN1_VALUE) sk, unsigned char *out,
	int skcontlen, const ASN1_ITEM *item, int do_sort) {
	// No need to sort if there are fewer than two items.
	if (!do_sort \|\| sk_ASN1_VALUE_num(sk) < 2) {
	for (size_t i = 0; i < sk_ASN1_VALUE_num(sk); i++) {
	ASN1_VALUE *skitem = sk_ASN1_VALUE_value(sk, i);
	if (ASN1_item_ex_i2d(&skitem, out, item, -1, 0) < 0) {
	return 0;
	}
	}
	return 1;
	}

	if (sk_ASN1_VALUE_num(sk) > ((size_t)-1) / sizeof(DER_ENC)) {
	OPENSSL_PUT_ERROR(ASN1, ERR_R_OVERFLOW);
	return 0;
	}

	int ret = 0;
	unsigned char *const buf = OPENSSL_malloc(skcontlen);
	DER_ENC encoded = OPENSSL_malloc(sk_ASN1_VALUE_num(sk) sizeof(*encoded));
	if (encoded == NULL \|\| buf == NULL) {
	OPENSSL_PUT_ERROR(ASN1, ERR_R_MALLOC_FAILURE);
	goto err;
	}

	// Encode all the elements into \|buf\| and populate \|encoded\|.
	unsigned char *p = buf;
	for (size_t i = 0; i < sk_ASN1_VALUE_num(sk); i++) {
	ASN1_VALUE *skitem = sk_ASN1_VALUE_value(sk, i);
	encoded[i].data = p;
	encoded[i].length = ASN1_item_ex_i2d(&skitem, &p, item, -1, 0);
	if (encoded[i].length < 0) {
	goto err;
	}
	assert(p - buf <= skcontlen);
	}

	qsort(encoded, sk_ASN1_VALUE_num(sk), sizeof(*encoded), der_cmp);

	// Output the elements in sorted order.
	p = *out;
	for (size_t i = 0; i < sk_ASN1_VALUE_num(sk); i++) {
	OPENSSL_memcpy(p, encoded[i].data, encoded[i].length);
	p += encoded[i].length;
	}
	*out = p;

	ret = 1;

	err:
	OPENSSL_free(encoded);
	OPENSSL_free(buf);
	return ret;
	}

	// asn1_i2d_ex_primitive behaves like \|ASN1_item_ex_i2d\| but \|item\| must be a
	// a PRIMITIVE or MSTRING type that is not an \|ASN1_ITEM_TEMPLATE\|.
	static int asn1_i2d_ex_primitive(ASN1_VALUE pval, unsigned char out,
	const ASN1_ITEM *it, int tag, int aclass,
	int optional) {
	// Get length of content octets and maybe find out the underlying type.
	int omit;
	int utype = it->utype;
	int len = asn1_ex_i2c(pval, NULL, &omit, &utype, it);
	if (len < 0) {
	return -1;
	}
	if (omit) {
	if (optional) {
	return 0;
	}
	OPENSSL_PUT_ERROR(ASN1, ASN1_R_MISSING_VALUE);
	return -1;
	}

	// If SEQUENCE, SET or OTHER then header is included in pseudo content
	// octets so don't include tag+length. We need to check here because the
	// call to asn1_ex_i2c() could change utype.
	int usetag =
	utype != V_ASN1_SEQUENCE && utype != V_ASN1_SET && utype != V_ASN1_OTHER;

	// If not implicitly tagged get tag from underlying type
	if (tag == -1) {
	tag = utype;
	}

	// Output tag+length followed by content octets
	if (out) {
	if (usetag) {
	ASN1_put_object(out, /constructed=/0, len, tag, aclass);
	}
	int len2 = asn1_ex_i2c(pval, *out, &omit, &utype, it);
	if (len2 < 0) {
	return -1;
	}
	assert(len == len2);
	assert(!omit);
	*out += len;
	}

	if (usetag) {
	return ASN1_object_size(/constructed=/0, len, tag);
	}
	return len;
	}

	// asn1_ex_i2c writes the \|*pval\| to \|cout\| under the i2d output convention,
	// excluding the tag and length. It returns the number of bytes written,
	// possibly zero, on success or -1 on error. If \|*pval\| should be omitted, it
	// returns zero and sets \|*out_omit\| to true.
	//
	// If \|it\| is an MSTRING or ANY type, it gets the underlying type from \|*pval\|,
	// which must be an \|ASN1_STRING\| or \|ASN1_TYPE\|, respectively. It then updates
	// \|*putype\| with the tag number of type used, or \|V_ASN1_OTHER\| if it was not a
	// universal type. If \|*putype\| is set to \|V_ASN1_SEQUENCE\|, \|V_ASN1_SET\|, or
	// \|V_ASN1_OTHER\|, it additionally outputs the tag and length, so the caller
	// must not do so.
	//
	// Otherwise, \|*putype\| must contain \|it->utype\|.
	//
	// WARNING: Unlike most functions in this file, \|asn1_ex_i2c\| can return zero
	// without omitting the element. ASN.1 values may have empty contents.
	static int asn1_ex_i2c(ASN1_VALUE *pval, unsigned char cout, int *out_omit,
	int putype, const ASN1_ITEM it) {
	ASN1_BOOLEAN *tbool = NULL;
	ASN1_STRING *strtmp;
	ASN1_OBJECT *otmp;
	int utype;
	const unsigned char *cont;
	unsigned char c;
	int len;

	// Historically, \|it->funcs\| for primitive types contained an
	// \|ASN1_PRIMITIVE_FUNCS\| table of callbacks.
	assert(it->funcs == NULL);

	*out_omit = 0;

	// Should type be omitted?
	if ((it->itype != ASN1_ITYPE_PRIMITIVE) \|\| (it->utype != V_ASN1_BOOLEAN)) {
	if (!*pval) {
	*out_omit = 1;
	return 0;
	}
	}

	if (it->itype == ASN1_ITYPE_MSTRING) {
	// If MSTRING type set the underlying type
	strtmp = (ASN1_STRING )pval;
	utype = strtmp->type;
	if (utype < 0 && utype != V_ASN1_OTHER) {
	// MSTRINGs can have type -1 when default-constructed.
	OPENSSL_PUT_ERROR(ASN1, ASN1_R_WRONG_TYPE);
	return -1;
	}
	// Negative INTEGER and ENUMERATED values use \|ASN1_STRING\| type values
	// that do not match their corresponding utype values. INTEGERs cannot
	// participate in MSTRING types, but ENUMERATEDs can.
	//
	// TODO(davidben): Is this a bug? Although arguably one of the MSTRING
	// types should contain more values, rather than less. See
	// https://crbug.com/boringssl/412. But it is not possible to fit all
	// possible ANY values into an \|ASN1_STRING\|, so matching the spec here
	// is somewhat hopeless.
	if (utype == V_ASN1_NEG_INTEGER) {
	utype = V_ASN1_INTEGER;
	} else if (utype == V_ASN1_NEG_ENUMERATED) {
	utype = V_ASN1_ENUMERATED;
	}
	*putype = utype;
	} else if (it->utype == V_ASN1_ANY) {
	// If ANY set type and pointer to value
	ASN1_TYPE *typ;
	typ = (ASN1_TYPE )pval;
	utype = typ->type;
	if (utype < 0 && utype != V_ASN1_OTHER) {
	// \|ASN1_TYPE\|s can have type -1 when default-constructed.
	OPENSSL_PUT_ERROR(ASN1, ASN1_R_WRONG_TYPE);
	return -1;
	}
	*putype = utype;
	pval = &typ->value.asn1_value;
	} else {
	utype = *putype;
	}

	switch (utype) {
	case V_ASN1_OBJECT:
	otmp = (ASN1_OBJECT )pval;
	cont = otmp->data;
	len = otmp->length;
	if (len == 0) {
	// Some \|ASN1_OBJECT\|s do not have OIDs and cannot be serialized.
	OPENSSL_PUT_ERROR(ASN1, ASN1_R_ILLEGAL_OBJECT);
	return -1;
	}
	break;

	case V_ASN1_NULL:
	cont = NULL;
	len = 0;
	break;

	case V_ASN1_BOOLEAN:
	tbool = (ASN1_BOOLEAN *)pval;
	if (*tbool == -1) {
	*out_omit = 1;
	return 0;
	}
	if (it->utype != V_ASN1_ANY) {
	// Default handling if value == size field then omit
	if ((tbool && (it->size > 0)) \|\| (!tbool && !it->size)) {
	*out_omit = 1;
	return 0;
	}
	}
	c = *tbool ? 0xff : 0x00;
	cont = &c;
	len = 1;
	break;

	case V_ASN1_BIT_STRING: {
	int ret =
	i2c_ASN1_BIT_STRING((ASN1_BIT_STRING )pval, cout ? &cout : NULL);
	// \|i2c_ASN1_BIT_STRING\| returns zero on error instead of -1.
	return ret <= 0 ? -1 : ret;
	}

	case V_ASN1_INTEGER:
	case V_ASN1_ENUMERATED: {
	// \|i2c_ASN1_INTEGER\| also handles ENUMERATED.
	int ret = i2c_ASN1_INTEGER((ASN1_INTEGER )pval, cout ? &cout : NULL);
	// \|i2c_ASN1_INTEGER\| returns zero on error instead of -1.
	return ret <= 0 ? -1 : ret;
	}

	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_SEQUENCE:
	case V_ASN1_SET:
	default:
	// All based on ASN1_STRING and handled the same
	strtmp = (ASN1_STRING )pval;
	cont = strtmp->data;
	len = strtmp->length;

	break;
	}
	if (cout && len) {
	OPENSSL_memcpy(cout, cont, len);
	}
	return len;
	}