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      1 /* Written by Nils Larsch for the OpenSSL project. */
      2 /* ====================================================================
      3  * Copyright (c) 2000-2003 The OpenSSL Project.  All rights reserved.
      4  *
      5  * Redistribution and use in source and binary forms, with or without
      6  * modification, are permitted provided that the following conditions
      7  * are met:
      8  *
      9  * 1. Redistributions of source code must retain the above copyright
     10  *    notice, this list of conditions and the following disclaimer.
     11  *
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in
     14  *    the documentation and/or other materials provided with the
     15  *    distribution.
     16  *
     17  * 3. All advertising materials mentioning features or use of this
     18  *    software must display the following acknowledgment:
     19  *    "This product includes software developed by the OpenSSL Project
     20  *    for use in the OpenSSL Toolkit. (http://www.OpenSSL.org/)"
     21  *
     22  * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
     23  *    endorse or promote products derived from this software without
     24  *    prior written permission. For written permission, please contact
     25  *    licensing (at) OpenSSL.org.
     26  *
     27  * 5. Products derived from this software may not be called "OpenSSL"
     28  *    nor may "OpenSSL" appear in their names without prior written
     29  *    permission of the OpenSSL Project.
     30  *
     31  * 6. Redistributions of any form whatsoever must retain the following
     32  *    acknowledgment:
     33  *    "This product includes software developed by the OpenSSL Project
     34  *    for use in the OpenSSL Toolkit (http://www.OpenSSL.org/)"
     35  *
     36  * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
     37  * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     38  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     39  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
     40  * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     41  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
     42  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
     43  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     44  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
     45  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     46  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
     47  * OF THE POSSIBILITY OF SUCH DAMAGE.
     48  * ====================================================================
     49  *
     50  * This product includes cryptographic software written by Eric Young
     51  * (eay (at) cryptsoft.com).  This product includes software written by Tim
     52  * Hudson (tjh (at) cryptsoft.com). */
     53 
     54 #include <openssl/ec.h>
     55 
     56 #include <limits.h>
     57 #include <string.h>
     58 
     59 #include <openssl/bytestring.h>
     60 #include <openssl/bn.h>
     61 #include <openssl/err.h>
     62 #include <openssl/mem.h>
     63 #include <openssl/nid.h>
     64 
     65 #include "../fipsmodule/ec/internal.h"
     66 #include "../bytestring/internal.h"
     67 #include "../internal.h"
     68 
     69 
     70 static const unsigned kParametersTag =
     71     CBS_ASN1_CONSTRUCTED | CBS_ASN1_CONTEXT_SPECIFIC | 0;
     72 static const unsigned kPublicKeyTag =
     73     CBS_ASN1_CONSTRUCTED | CBS_ASN1_CONTEXT_SPECIFIC | 1;
     74 
     75 EC_KEY *EC_KEY_parse_private_key(CBS *cbs, const EC_GROUP *group) {
     76   CBS ec_private_key, private_key;
     77   uint64_t version;
     78   if (!CBS_get_asn1(cbs, &ec_private_key, CBS_ASN1_SEQUENCE) ||
     79       !CBS_get_asn1_uint64(&ec_private_key, &version) ||
     80       version != 1 ||
     81       !CBS_get_asn1(&ec_private_key, &private_key, CBS_ASN1_OCTETSTRING)) {
     82     OPENSSL_PUT_ERROR(EC, EC_R_DECODE_ERROR);
     83     return NULL;
     84   }
     85 
     86   // Parse the optional parameters field.
     87   EC_GROUP *inner_group = NULL;
     88   EC_KEY *ret = NULL;
     89   if (CBS_peek_asn1_tag(&ec_private_key, kParametersTag)) {
     90     // Per SEC 1, as an alternative to omitting it, one is allowed to specify
     91     // this field and put in a NULL to mean inheriting this value. This was
     92     // omitted in a previous version of this logic without problems, so leave it
     93     // unimplemented.
     94     CBS child;
     95     if (!CBS_get_asn1(&ec_private_key, &child, kParametersTag)) {
     96       OPENSSL_PUT_ERROR(EC, EC_R_DECODE_ERROR);
     97       goto err;
     98     }
     99     inner_group = EC_KEY_parse_parameters(&child);
    100     if (inner_group == NULL) {
    101       goto err;
    102     }
    103     if (group == NULL) {
    104       group = inner_group;
    105     } else if (EC_GROUP_cmp(group, inner_group, NULL) != 0) {
    106       // If a group was supplied externally, it must match.
    107       OPENSSL_PUT_ERROR(EC, EC_R_GROUP_MISMATCH);
    108       goto err;
    109     }
    110     if (CBS_len(&child) != 0) {
    111       OPENSSL_PUT_ERROR(EC, EC_R_DECODE_ERROR);
    112       goto err;
    113     }
    114   }
    115 
    116   if (group == NULL) {
    117     OPENSSL_PUT_ERROR(EC, EC_R_MISSING_PARAMETERS);
    118     goto err;
    119   }
    120 
    121   ret = EC_KEY_new();
    122   if (ret == NULL || !EC_KEY_set_group(ret, group)) {
    123     goto err;
    124   }
    125 
    126   // Although RFC 5915 specifies the length of the key, OpenSSL historically
    127   // got this wrong, so accept any length. See upstream's
    128   // 30cd4ff294252c4b6a4b69cbef6a5b4117705d22.
    129   ret->priv_key =
    130       BN_bin2bn(CBS_data(&private_key), CBS_len(&private_key), NULL);
    131   ret->pub_key = EC_POINT_new(group);
    132   if (ret->priv_key == NULL || ret->pub_key == NULL) {
    133     goto err;
    134   }
    135 
    136   if (BN_cmp(ret->priv_key, EC_GROUP_get0_order(group)) >= 0) {
    137     OPENSSL_PUT_ERROR(EC, EC_R_WRONG_ORDER);
    138     goto err;
    139   }
    140 
    141   if (CBS_peek_asn1_tag(&ec_private_key, kPublicKeyTag)) {
    142     CBS child, public_key;
    143     uint8_t padding;
    144     if (!CBS_get_asn1(&ec_private_key, &child, kPublicKeyTag) ||
    145         !CBS_get_asn1(&child, &public_key, CBS_ASN1_BITSTRING) ||
    146         // As in a SubjectPublicKeyInfo, the byte-encoded public key is then
    147         // encoded as a BIT STRING with bits ordered as in the DER encoding.
    148         !CBS_get_u8(&public_key, &padding) ||
    149         padding != 0 ||
    150         // Explicitly check |public_key| is non-empty to save the conversion
    151         // form later.
    152         CBS_len(&public_key) == 0 ||
    153         !EC_POINT_oct2point(group, ret->pub_key, CBS_data(&public_key),
    154                             CBS_len(&public_key), NULL) ||
    155         CBS_len(&child) != 0) {
    156       OPENSSL_PUT_ERROR(EC, EC_R_DECODE_ERROR);
    157       goto err;
    158     }
    159 
    160     // Save the point conversion form.
    161     // TODO(davidben): Consider removing this.
    162     ret->conv_form =
    163         (point_conversion_form_t)(CBS_data(&public_key)[0] & ~0x01);
    164   } else {
    165     // Compute the public key instead.
    166     if (!EC_POINT_mul(group, ret->pub_key, ret->priv_key, NULL, NULL, NULL)) {
    167       goto err;
    168     }
    169     // Remember the original private-key-only encoding.
    170     // TODO(davidben): Consider removing this.
    171     ret->enc_flag |= EC_PKEY_NO_PUBKEY;
    172   }
    173 
    174   if (CBS_len(&ec_private_key) != 0) {
    175     OPENSSL_PUT_ERROR(EC, EC_R_DECODE_ERROR);
    176     goto err;
    177   }
    178 
    179   // Ensure the resulting key is valid.
    180   if (!EC_KEY_check_key(ret)) {
    181     goto err;
    182   }
    183 
    184   EC_GROUP_free(inner_group);
    185   return ret;
    186 
    187 err:
    188   EC_KEY_free(ret);
    189   EC_GROUP_free(inner_group);
    190   return NULL;
    191 }
    192 
    193 int EC_KEY_marshal_private_key(CBB *cbb, const EC_KEY *key,
    194                                unsigned enc_flags) {
    195   if (key == NULL || key->group == NULL || key->priv_key == NULL) {
    196     OPENSSL_PUT_ERROR(EC, ERR_R_PASSED_NULL_PARAMETER);
    197     return 0;
    198   }
    199 
    200   CBB ec_private_key, private_key;
    201   if (!CBB_add_asn1(cbb, &ec_private_key, CBS_ASN1_SEQUENCE) ||
    202       !CBB_add_asn1_uint64(&ec_private_key, 1 /* version */) ||
    203       !CBB_add_asn1(&ec_private_key, &private_key, CBS_ASN1_OCTETSTRING) ||
    204       !BN_bn2cbb_padded(&private_key,
    205                         BN_num_bytes(EC_GROUP_get0_order(key->group)),
    206                         key->priv_key)) {
    207     OPENSSL_PUT_ERROR(EC, EC_R_ENCODE_ERROR);
    208     return 0;
    209   }
    210 
    211   if (!(enc_flags & EC_PKEY_NO_PARAMETERS)) {
    212     CBB child;
    213     if (!CBB_add_asn1(&ec_private_key, &child, kParametersTag) ||
    214         !EC_KEY_marshal_curve_name(&child, key->group) ||
    215         !CBB_flush(&ec_private_key)) {
    216       OPENSSL_PUT_ERROR(EC, EC_R_ENCODE_ERROR);
    217       return 0;
    218     }
    219   }
    220 
    221   // TODO(fork): replace this flexibility with sensible default?
    222   if (!(enc_flags & EC_PKEY_NO_PUBKEY) && key->pub_key != NULL) {
    223     CBB child, public_key;
    224     if (!CBB_add_asn1(&ec_private_key, &child, kPublicKeyTag) ||
    225         !CBB_add_asn1(&child, &public_key, CBS_ASN1_BITSTRING) ||
    226         // As in a SubjectPublicKeyInfo, the byte-encoded public key is then
    227         // encoded as a BIT STRING with bits ordered as in the DER encoding.
    228         !CBB_add_u8(&public_key, 0 /* padding */) ||
    229         !EC_POINT_point2cbb(&public_key, key->group, key->pub_key,
    230                             key->conv_form, NULL) ||
    231         !CBB_flush(&ec_private_key)) {
    232       OPENSSL_PUT_ERROR(EC, EC_R_ENCODE_ERROR);
    233       return 0;
    234     }
    235   }
    236 
    237   if (!CBB_flush(cbb)) {
    238     OPENSSL_PUT_ERROR(EC, EC_R_ENCODE_ERROR);
    239     return 0;
    240   }
    241 
    242   return 1;
    243 }
    244 
    245 // is_unsigned_integer returns one if |cbs| is a valid unsigned DER INTEGER and
    246 // zero otherwise.
    247 static int is_unsigned_integer(const CBS *cbs) {
    248   if (CBS_len(cbs) == 0) {
    249     return 0;
    250   }
    251   uint8_t byte = CBS_data(cbs)[0];
    252   if ((byte & 0x80) ||
    253       (byte == 0 && CBS_len(cbs) > 1 && (CBS_data(cbs)[1] & 0x80) == 0)) {
    254     // Negative or not minimally-encoded.
    255     return 0;
    256   }
    257   return 1;
    258 }
    259 
    260 // kPrimeFieldOID is the encoding of 1.2.840.10045.1.1.
    261 static const uint8_t kPrimeField[] = {0x2a, 0x86, 0x48, 0xce, 0x3d, 0x01, 0x01};
    262 
    263 static int parse_explicit_prime_curve(CBS *in, CBS *out_prime, CBS *out_a,
    264                                       CBS *out_b, CBS *out_base_x,
    265                                       CBS *out_base_y, CBS *out_order) {
    266   // See RFC 3279, section 2.3.5. Note that RFC 3279 calls this structure an
    267   // ECParameters while RFC 5480 calls it a SpecifiedECDomain.
    268   CBS params, field_id, field_type, curve, base;
    269   uint64_t version;
    270   if (!CBS_get_asn1(in, &params, CBS_ASN1_SEQUENCE) ||
    271       !CBS_get_asn1_uint64(&params, &version) ||
    272       version != 1 ||
    273       !CBS_get_asn1(&params, &field_id, CBS_ASN1_SEQUENCE) ||
    274       !CBS_get_asn1(&field_id, &field_type, CBS_ASN1_OBJECT) ||
    275       CBS_len(&field_type) != sizeof(kPrimeField) ||
    276       OPENSSL_memcmp(CBS_data(&field_type), kPrimeField, sizeof(kPrimeField)) != 0 ||
    277       !CBS_get_asn1(&field_id, out_prime, CBS_ASN1_INTEGER) ||
    278       !is_unsigned_integer(out_prime) ||
    279       CBS_len(&field_id) != 0 ||
    280       !CBS_get_asn1(&params, &curve, CBS_ASN1_SEQUENCE) ||
    281       !CBS_get_asn1(&curve, out_a, CBS_ASN1_OCTETSTRING) ||
    282       !CBS_get_asn1(&curve, out_b, CBS_ASN1_OCTETSTRING) ||
    283       // |curve| has an optional BIT STRING seed which we ignore.
    284       !CBS_get_asn1(&params, &base, CBS_ASN1_OCTETSTRING) ||
    285       !CBS_get_asn1(&params, out_order, CBS_ASN1_INTEGER) ||
    286       !is_unsigned_integer(out_order)) {
    287     OPENSSL_PUT_ERROR(EC, EC_R_DECODE_ERROR);
    288     return 0;
    289   }
    290 
    291   // |params| has an optional cofactor which we ignore. With the optional seed
    292   // in |curve|, a group already has arbitrarily many encodings. Parse enough to
    293   // uniquely determine the curve.
    294 
    295   // Require that the base point use uncompressed form.
    296   uint8_t form;
    297   if (!CBS_get_u8(&base, &form) || form != POINT_CONVERSION_UNCOMPRESSED) {
    298     OPENSSL_PUT_ERROR(EC, EC_R_INVALID_FORM);
    299     return 0;
    300   }
    301 
    302   if (CBS_len(&base) % 2 != 0) {
    303     OPENSSL_PUT_ERROR(EC, EC_R_DECODE_ERROR);
    304     return 0;
    305   }
    306   size_t field_len = CBS_len(&base) / 2;
    307   CBS_init(out_base_x, CBS_data(&base), field_len);
    308   CBS_init(out_base_y, CBS_data(&base) + field_len, field_len);
    309 
    310   return 1;
    311 }
    312 
    313 // integers_equal returns one if |a| and |b| are equal, up to leading zeros, and
    314 // zero otherwise.
    315 static int integers_equal(const CBS *a, const uint8_t *b, size_t b_len) {
    316   // Remove leading zeros from |a| and |b|.
    317   CBS a_copy = *a;
    318   while (CBS_len(&a_copy) > 0 && CBS_data(&a_copy)[0] == 0) {
    319     CBS_skip(&a_copy, 1);
    320   }
    321   while (b_len > 0 && b[0] == 0) {
    322     b++;
    323     b_len--;
    324   }
    325   return CBS_mem_equal(&a_copy, b, b_len);
    326 }
    327 
    328 EC_GROUP *EC_KEY_parse_curve_name(CBS *cbs) {
    329   CBS named_curve;
    330   if (!CBS_get_asn1(cbs, &named_curve, CBS_ASN1_OBJECT)) {
    331     OPENSSL_PUT_ERROR(EC, EC_R_DECODE_ERROR);
    332     return NULL;
    333   }
    334 
    335   // Look for a matching curve.
    336   const struct built_in_curves *const curves = OPENSSL_built_in_curves();
    337   for (size_t i = 0; i < OPENSSL_NUM_BUILT_IN_CURVES; i++) {
    338     const struct built_in_curve *curve = &curves->curves[i];
    339     if (CBS_len(&named_curve) == curve->oid_len &&
    340         OPENSSL_memcmp(CBS_data(&named_curve), curve->oid, curve->oid_len) ==
    341             0) {
    342       return EC_GROUP_new_by_curve_name(curve->nid);
    343     }
    344   }
    345 
    346   OPENSSL_PUT_ERROR(EC, EC_R_UNKNOWN_GROUP);
    347   return NULL;
    348 }
    349 
    350 int EC_KEY_marshal_curve_name(CBB *cbb, const EC_GROUP *group) {
    351   int nid = EC_GROUP_get_curve_name(group);
    352   if (nid == NID_undef) {
    353     OPENSSL_PUT_ERROR(EC, EC_R_UNKNOWN_GROUP);
    354     return 0;
    355   }
    356 
    357   const struct built_in_curves *const curves = OPENSSL_built_in_curves();
    358   for (size_t i = 0; i < OPENSSL_NUM_BUILT_IN_CURVES; i++) {
    359     const struct built_in_curve *curve = &curves->curves[i];
    360     if (curve->nid == nid) {
    361       CBB child;
    362       return CBB_add_asn1(cbb, &child, CBS_ASN1_OBJECT) &&
    363              CBB_add_bytes(&child, curve->oid, curve->oid_len) &&
    364              CBB_flush(cbb);
    365     }
    366   }
    367 
    368   OPENSSL_PUT_ERROR(EC, EC_R_UNKNOWN_GROUP);
    369   return 0;
    370 }
    371 
    372 EC_GROUP *EC_KEY_parse_parameters(CBS *cbs) {
    373   if (!CBS_peek_asn1_tag(cbs, CBS_ASN1_SEQUENCE)) {
    374     return EC_KEY_parse_curve_name(cbs);
    375   }
    376 
    377   // OpenSSL sometimes produces ECPrivateKeys with explicitly-encoded versions
    378   // of named curves.
    379   //
    380   // TODO(davidben): Remove support for this.
    381   CBS prime, a, b, base_x, base_y, order;
    382   if (!parse_explicit_prime_curve(cbs, &prime, &a, &b, &base_x, &base_y,
    383                                   &order)) {
    384     return NULL;
    385   }
    386 
    387   // Look for a matching prime curve.
    388   const struct built_in_curves *const curves = OPENSSL_built_in_curves();
    389   for (size_t i = 0; i < OPENSSL_NUM_BUILT_IN_CURVES; i++) {
    390     const struct built_in_curve *curve = &curves->curves[i];
    391     const unsigned param_len = curve->param_len;
    392     // |curve->params| is ordered p, a, b, x, y, order, each component
    393     // zero-padded up to the field length. Although SEC 1 states that the
    394     // Field-Element-to-Octet-String conversion also pads, OpenSSL mis-encodes
    395     // |a| and |b|, so this comparison must allow omitting leading zeros. (This
    396     // is relevant for P-521 whose |b| has a leading 0.)
    397     if (integers_equal(&prime, curve->params, param_len) &&
    398         integers_equal(&a, curve->params + param_len, param_len) &&
    399         integers_equal(&b, curve->params + param_len * 2, param_len) &&
    400         integers_equal(&base_x, curve->params + param_len * 3, param_len) &&
    401         integers_equal(&base_y, curve->params + param_len * 4, param_len) &&
    402         integers_equal(&order, curve->params + param_len * 5, param_len)) {
    403       return EC_GROUP_new_by_curve_name(curve->nid);
    404     }
    405   }
    406 
    407   OPENSSL_PUT_ERROR(EC, EC_R_UNKNOWN_GROUP);
    408   return NULL;
    409 }
    410 
    411 int EC_POINT_point2cbb(CBB *out, const EC_GROUP *group, const EC_POINT *point,
    412                        point_conversion_form_t form, BN_CTX *ctx) {
    413   size_t len = EC_POINT_point2oct(group, point, form, NULL, 0, ctx);
    414   if (len == 0) {
    415     return 0;
    416   }
    417   uint8_t *p;
    418   return CBB_add_space(out, &p, len) &&
    419          EC_POINT_point2oct(group, point, form, p, len, ctx) == len;
    420 }
    421 
    422 EC_KEY *d2i_ECPrivateKey(EC_KEY **out, const uint8_t **inp, long len) {
    423   // This function treats its |out| parameter differently from other |d2i|
    424   // functions. If supplied, take the group from |*out|.
    425   const EC_GROUP *group = NULL;
    426   if (out != NULL && *out != NULL) {
    427     group = EC_KEY_get0_group(*out);
    428   }
    429 
    430   if (len < 0) {
    431     OPENSSL_PUT_ERROR(EC, EC_R_DECODE_ERROR);
    432     return NULL;
    433   }
    434   CBS cbs;
    435   CBS_init(&cbs, *inp, (size_t)len);
    436   EC_KEY *ret = EC_KEY_parse_private_key(&cbs, group);
    437   if (ret == NULL) {
    438     return NULL;
    439   }
    440   if (out != NULL) {
    441     EC_KEY_free(*out);
    442     *out = ret;
    443   }
    444   *inp = CBS_data(&cbs);
    445   return ret;
    446 }
    447 
    448 int i2d_ECPrivateKey(const EC_KEY *key, uint8_t **outp) {
    449   CBB cbb;
    450   if (!CBB_init(&cbb, 0) ||
    451       !EC_KEY_marshal_private_key(&cbb, key, EC_KEY_get_enc_flags(key))) {
    452     CBB_cleanup(&cbb);
    453     return -1;
    454   }
    455   return CBB_finish_i2d(&cbb, outp);
    456 }
    457 
    458 EC_KEY *d2i_ECParameters(EC_KEY **out_key, const uint8_t **inp, long len) {
    459   if (len < 0) {
    460     return NULL;
    461   }
    462 
    463   CBS cbs;
    464   CBS_init(&cbs, *inp, (size_t)len);
    465   EC_GROUP *group = EC_KEY_parse_parameters(&cbs);
    466   if (group == NULL) {
    467     return NULL;
    468   }
    469 
    470   EC_KEY *ret = EC_KEY_new();
    471   if (ret == NULL || !EC_KEY_set_group(ret, group)) {
    472     EC_GROUP_free(group);
    473     EC_KEY_free(ret);
    474     return NULL;
    475   }
    476   EC_GROUP_free(group);
    477 
    478   if (out_key != NULL) {
    479     EC_KEY_free(*out_key);
    480     *out_key = ret;
    481   }
    482   *inp = CBS_data(&cbs);
    483   return ret;
    484 }
    485 
    486 int i2d_ECParameters(const EC_KEY *key, uint8_t **outp) {
    487   if (key == NULL || key->group == NULL) {
    488     OPENSSL_PUT_ERROR(EC, ERR_R_PASSED_NULL_PARAMETER);
    489     return -1;
    490   }
    491 
    492   CBB cbb;
    493   if (!CBB_init(&cbb, 0) ||
    494       !EC_KEY_marshal_curve_name(&cbb, key->group)) {
    495     CBB_cleanup(&cbb);
    496     return -1;
    497   }
    498   return CBB_finish_i2d(&cbb, outp);
    499 }
    500 
    501 EC_KEY *o2i_ECPublicKey(EC_KEY **keyp, const uint8_t **inp, long len) {
    502   EC_KEY *ret = NULL;
    503 
    504   if (keyp == NULL || *keyp == NULL || (*keyp)->group == NULL) {
    505     OPENSSL_PUT_ERROR(EC, ERR_R_PASSED_NULL_PARAMETER);
    506     return NULL;
    507   }
    508   ret = *keyp;
    509   if (ret->pub_key == NULL &&
    510       (ret->pub_key = EC_POINT_new(ret->group)) == NULL) {
    511     OPENSSL_PUT_ERROR(EC, ERR_R_MALLOC_FAILURE);
    512     return NULL;
    513   }
    514   if (!EC_POINT_oct2point(ret->group, ret->pub_key, *inp, len, NULL)) {
    515     OPENSSL_PUT_ERROR(EC, ERR_R_EC_LIB);
    516     return NULL;
    517   }
    518   // save the point conversion form
    519   ret->conv_form = (point_conversion_form_t)(*inp[0] & ~0x01);
    520   *inp += len;
    521   return ret;
    522 }
    523 
    524 int i2o_ECPublicKey(const EC_KEY *key, uint8_t **outp) {
    525   size_t buf_len = 0;
    526   int new_buffer = 0;
    527 
    528   if (key == NULL) {
    529     OPENSSL_PUT_ERROR(EC, ERR_R_PASSED_NULL_PARAMETER);
    530     return 0;
    531   }
    532 
    533   buf_len = EC_POINT_point2oct(key->group, key->pub_key, key->conv_form, NULL,
    534                                0, NULL);
    535 
    536   if (outp == NULL || buf_len == 0) {
    537     // out == NULL => just return the length of the octet string
    538     return buf_len;
    539   }
    540 
    541   if (*outp == NULL) {
    542     *outp = OPENSSL_malloc(buf_len);
    543     if (*outp == NULL) {
    544       OPENSSL_PUT_ERROR(EC, ERR_R_MALLOC_FAILURE);
    545       return 0;
    546     }
    547     new_buffer = 1;
    548   }
    549   if (!EC_POINT_point2oct(key->group, key->pub_key, key->conv_form, *outp,
    550                           buf_len, NULL)) {
    551     OPENSSL_PUT_ERROR(EC, ERR_R_EC_LIB);
    552     if (new_buffer) {
    553       OPENSSL_free(*outp);
    554       *outp = NULL;
    555     }
    556     return 0;
    557   }
    558 
    559   if (!new_buffer) {
    560     *outp += buf_len;
    561   }
    562   return buf_len;
    563 }
    564