* This parses a format loosely based on a DER encoding of the ECPrivateKey type from * section C.4 of SEC 1 , with the following caveats: * * * The octet-length of the SEQUENCE must be encoded as 1 or 2 octets. It is not * required to be encoded as one octet if it is less than 256, as DER would require. * * The octet-length of the SEQUENCE must not be great
| 36 | * out32 must point to an output buffer of length at least 32 bytes. |
| 37 | */ |
| 38 | int ec_seckey_import_der(const secp256k1_context* ctx, unsigned char *out32, const unsigned char *seckey, size_t seckeylen) { |
| 39 | const unsigned char *end = seckey + seckeylen; |
| 40 | memset(out32, 0, 32); |
| 41 | /* sequence header */ |
| 42 | if (end - seckey < 1 || *seckey != 0x30u) { |
| 43 | return 0; |
| 44 | } |
| 45 | seckey++; |
| 46 | /* sequence length constructor */ |
| 47 | if (end - seckey < 1 || !(*seckey & 0x80u)) { |
| 48 | return 0; |
| 49 | } |
| 50 | ptrdiff_t lenb = *seckey & ~0x80u; seckey++; |
| 51 | if (lenb < 1 || lenb > 2) { |
| 52 | return 0; |
| 53 | } |
| 54 | if (end - seckey < lenb) { |
| 55 | return 0; |
| 56 | } |
| 57 | /* sequence length */ |
| 58 | ptrdiff_t len = seckey[lenb-1] | (lenb > 1 ? seckey[lenb-2] << 8 : 0u); |
| 59 | seckey += lenb; |
| 60 | if (end - seckey < len) { |
| 61 | return 0; |
| 62 | } |
| 63 | /* sequence element 0: version number (=1) */ |
| 64 | if (end - seckey < 3 || seckey[0] != 0x02u || seckey[1] != 0x01u || seckey[2] != 0x01u) { |
| 65 | return 0; |
| 66 | } |
| 67 | seckey += 3; |
| 68 | /* sequence element 1: octet string, up to 32 bytes */ |
| 69 | if (end - seckey < 2 || seckey[0] != 0x04u) { |
| 70 | return 0; |
| 71 | } |
| 72 | ptrdiff_t oslen = seckey[1]; |
| 73 | seckey += 2; |
| 74 | if (oslen > 32 || end - seckey < oslen) { |
| 75 | return 0; |
| 76 | } |
| 77 | memcpy(out32 + (32 - oslen), seckey, oslen); |
| 78 | if (!secp256k1_ec_seckey_verify(ctx, out32)) { |
| 79 | memset(out32, 0, 32); |
| 80 | return 0; |
| 81 | } |
| 82 | return 1; |
| 83 | } |
| 84 | |
| 85 | /** |
| 86 | * This serializes to a DER encoding of the ECPrivateKey type from section C.4 of SEC 1 |