1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis */
2 /* SPDX-License-Identifier: Unlicense */
3
4 #include "tomcrypt_private.h"
5
6 #ifdef LTC_MECC
7
8 /**
9 Export an ECC key as a binary packet
10 @param out [out] Destination for the key
11 @param outlen [in/out] Max size and resulting size of the exported key
12 @param type The type of key you want to export (PK_PRIVATE or PK_PUBLIC)
13 @param key The key to export
14 @return CRYPT_OK if successful
15 */
16
ecc_export_openssl(unsigned char * out,unsigned long * outlen,int type,const ecc_key * key)17 int ecc_export_openssl(unsigned char *out, unsigned long *outlen, int type, const ecc_key *key)
18 {
19 int err;
20 void *prime, *order, *a, *b, *gx, *gy;
21 unsigned char bin_a[256], bin_b[256], bin_k[256], bin_g[512], bin_xy[512];
22 unsigned long len_a, len_b, len_k, len_g, len_xy;
23 unsigned long cofactor, one = 1;
24 const char *OID;
25 unsigned long oid[16], oidlen;
26 ltc_asn1_list seq_fieldid[2], seq_curve[2], seq_ecparams[6], seq_priv[4], pub_xy, ecparams;
27 int flag_oid = type & PK_CURVEOID ? 1 : 0;
28 int flag_com = type & PK_COMPRESSED ? 1 : 0;
29 int flag_pri = type & PK_PRIVATE ? 1 : 0;
30
31 LTC_ARGCHK(out != NULL);
32 LTC_ARGCHK(outlen != NULL);
33 LTC_ARGCHK(key != NULL);
34
35 if (key->type != PK_PRIVATE && flag_pri) return CRYPT_PK_TYPE_MISMATCH;
36
37 if (flag_oid) {
38 /* http://tools.ietf.org/html/rfc5912
39 ECParameters ::= CHOICE {
40 namedCurve CURVE.&id({NamedCurve}) # OBJECT
41 }
42 */
43 if (key->dp.oidlen == 0) { err = CRYPT_INVALID_ARG; goto error; }
44 LTC_SET_ASN1(&ecparams, 0, LTC_ASN1_OBJECT_IDENTIFIER, key->dp.oid, key->dp.oidlen);
45 }
46 else {
47 prime = key->dp.prime;
48 order = key->dp.order;
49 a = key->dp.A;
50 b = key->dp.B;
51 gx = key->dp.base.x;
52 gy = key->dp.base.y;
53 cofactor = key->dp.cofactor;
54
55 /* curve param a */
56 len_a = mp_unsigned_bin_size(a);
57 if (len_a > sizeof(bin_a)) { err = CRYPT_BUFFER_OVERFLOW; goto error; }
58 if ((err = mp_to_unsigned_bin(a, bin_a)) != CRYPT_OK) { goto error; }
59 if (len_a == 0) { len_a = 1; bin_a[0] = 0; } /* handle case a == 0 */
60
61 /* curve param b */
62 len_b = mp_unsigned_bin_size(b);
63 if (len_b > sizeof(bin_b)) { err = CRYPT_BUFFER_OVERFLOW; goto error; }
64 if ((err = mp_to_unsigned_bin(b, bin_b)) != CRYPT_OK) { goto error; }
65 if (len_b == 0) { len_b = 1; bin_b[0] = 0; } /* handle case b == 0 */
66
67 /* base point - (un)compressed based on flag_com */
68 len_g = sizeof(bin_g);
69 err = ltc_ecc_export_point(bin_g, &len_g, gx, gy, key->dp.size, flag_com);
70 if (err != CRYPT_OK) { goto error; }
71
72 /* we support only prime-field EC */
73 if ((err = pk_get_oid(LTC_OID_EC_PRIMEF, &OID)) != CRYPT_OK) { goto error; }
74
75 /* http://tools.ietf.org/html/rfc3279
76 ECParameters ::= SEQUENCE { # SEQUENCE
77 version INTEGER { ecpVer1(1) } (ecpVer1) # INTEGER :01
78 FieldID ::= SEQUENCE { # SEQUENCE
79 fieldType FIELD-ID.&id({IOSet}), # OBJECT :prime-field
80 parameters FIELD-ID.&Type({IOSet}{@fieldType}) # INTEGER
81 }
82 Curve ::= SEQUENCE { # SEQUENCE
83 a FieldElement ::= OCTET STRING # OCTET STRING
84 b FieldElement ::= OCTET STRING # OCTET STRING
85 seed BIT STRING OPTIONAL
86 }
87 base ECPoint ::= OCTET STRING # OCTET STRING
88 order INTEGER, # INTEGER
89 cofactor INTEGER OPTIONAL # INTEGER
90 }
91 */
92
93 oidlen = sizeof(oid)/sizeof(oid[0]);
94 if ((err = pk_oid_str_to_num(OID, oid, &oidlen)) != CRYPT_OK) {
95 goto error;
96 }
97
98 /* FieldID SEQUENCE */
99 LTC_SET_ASN1(seq_fieldid, 0, LTC_ASN1_OBJECT_IDENTIFIER, oid, oidlen);
100 LTC_SET_ASN1(seq_fieldid, 1, LTC_ASN1_INTEGER, prime, 1UL);
101
102 /* Curve SEQUENCE */
103 LTC_SET_ASN1(seq_curve, 0, LTC_ASN1_OCTET_STRING, bin_a, len_a);
104 LTC_SET_ASN1(seq_curve, 1, LTC_ASN1_OCTET_STRING, bin_b, len_b);
105
106 /* ECParameters SEQUENCE */
107 LTC_SET_ASN1(seq_ecparams, 0, LTC_ASN1_SHORT_INTEGER, &one, 1UL);
108 LTC_SET_ASN1(seq_ecparams, 1, LTC_ASN1_SEQUENCE, seq_fieldid, 2UL);
109 LTC_SET_ASN1(seq_ecparams, 2, LTC_ASN1_SEQUENCE, seq_curve, 2UL);
110 LTC_SET_ASN1(seq_ecparams, 3, LTC_ASN1_OCTET_STRING, bin_g, len_g);
111 LTC_SET_ASN1(seq_ecparams, 4, LTC_ASN1_INTEGER, order, 1UL);
112 LTC_SET_ASN1(seq_ecparams, 5, LTC_ASN1_SHORT_INTEGER, &cofactor, 1UL);
113
114 /* ECParameters used by ECPrivateKey or SubjectPublicKeyInfo below */
115 LTC_SET_ASN1(&ecparams, 0, LTC_ASN1_SEQUENCE, seq_ecparams, 6UL);
116 }
117
118 /* public key - (un)compressed based on flag_com */
119 len_xy = sizeof(bin_xy);
120 err = ltc_ecc_export_point(bin_xy, &len_xy, key->pubkey.x, key->pubkey.y, key->dp.size, flag_com);
121 if (err != CRYPT_OK) {
122 goto error;
123 }
124
125 if (flag_pri) {
126
127 /* http://tools.ietf.org/html/rfc5915
128 ECPrivateKey ::= SEQUENCE { # SEQUENCE
129 version INTEGER { ecPrivkeyVer1(1) } (ecPrivkeyVer1) # INTEGER :01
130 privateKey OCTET STRING, # OCTET STRING
131 [0] ECParameters # see above
132 [1] publicKey # BIT STRING
133 }
134 */
135
136 /* private key */
137 len_k = mp_unsigned_bin_size(key->k);
138 if (len_k > sizeof(bin_k)) { err = CRYPT_BUFFER_OVERFLOW; goto error; }
139 if ((err = mp_to_unsigned_bin(key->k, bin_k)) != CRYPT_OK) { goto error; }
140
141 LTC_SET_ASN1(&pub_xy, 0, LTC_ASN1_RAW_BIT_STRING, bin_xy, 8*len_xy);
142 LTC_SET_ASN1(seq_priv, 0, LTC_ASN1_SHORT_INTEGER, &one, 1);
143 LTC_SET_ASN1(seq_priv, 1, LTC_ASN1_OCTET_STRING, bin_k, len_k);
144 LTC_SET_ASN1_CUSTOM_CONSTRUCTED(seq_priv, 2, LTC_ASN1_CL_CONTEXT_SPECIFIC, 0, &ecparams); /* context specific 0 */
145 LTC_SET_ASN1_CUSTOM_CONSTRUCTED(seq_priv, 3, LTC_ASN1_CL_CONTEXT_SPECIFIC, 1, &pub_xy); /* context specific 1 */
146
147 err = der_encode_sequence(seq_priv, 4, out, outlen);
148 }
149 else {
150 /* http://tools.ietf.org/html/rfc5480
151 SubjectPublicKeyInfo ::= SEQUENCE { # SEQUENCE
152 AlgorithmIdentifier ::= SEQUENCE { # SEQUENCE
153 algorithm OBJECT IDENTIFIER # OBJECT :id-ecPublicKey
154 ECParameters # see above
155 }
156 subjectPublicKey BIT STRING # BIT STRING
157 }
158 */
159 err = x509_encode_subject_public_key_info( out, outlen, LTC_OID_EC, bin_xy, len_xy,
160 ecparams.type, ecparams.data, ecparams.size );
161 }
162
163 error:
164 return err;
165 }
166
167 #endif
168