diff options
Diffstat (limited to 'asn1.c')
| -rw-r--r-- | asn1.c | 144 |
1 files changed, 144 insertions, 0 deletions
@@ -175,6 +175,88 @@ hal_error_t hal_asn1_encode_integer(const fp_int * const bn, } /* + * Encode an unsigned ASN.1 INTEGER from a uint32_t. If der is + * NULL, just return the length of what we would have encoded. + */ + +hal_error_t hal_asn1_encode_uint32(const uint32_t n, + uint8_t *der, size_t *der_len, const size_t der_max) +{ + /* + * We only handle unsigned INTEGERs, so we need to pad data with a + * leading zero if the most significant bit is set, to avoid + * flipping the ASN.1 sign bit. + */ + + size_t vlen; + hal_error_t err; + size_t hlen; + + /* DER says to use the minimum number of octets */ + if (n < 0x80) vlen = 1; + else if (n < 0x8000) vlen = 2; + else if (n < 0x800000) vlen = 3; + else if (n < 0x80000000) vlen = 4; + else vlen = 5; + + err = hal_asn1_encode_header(ASN1_INTEGER, vlen, der, &hlen, der_max); + + if (der_len != NULL) + *der_len = hlen + vlen; + + if (der == NULL || err != HAL_OK) + return err; + + assert(hlen + vlen <= der_max); + + der += hlen; + + uint32_t m = n; + for (size_t i = vlen; i > 0; --i) { + der[i - 1] = m & 0xff; + m >>= 8; + } + + return HAL_OK; +} + +/* + * Encode an ASN.1 OCTET STRING. If der is NULL, just return the length + * of what we would have encoded. + */ + +hal_error_t hal_asn1_encode_octet_string(const uint8_t * const data, const size_t data_len, + uint8_t *der, size_t *der_len, const size_t der_max) +{ + if (data_len == 0 || (der != NULL && data == NULL)) + return HAL_ERROR_BAD_ARGUMENTS; + + size_t hlen; + hal_error_t err; + + if ((err = hal_asn1_encode_header(ASN1_OCTET_STRING, data_len, NULL, &hlen, 0)) != HAL_OK) + return err; + + if (der_len != NULL) + *der_len = hlen + data_len; + + if (der == NULL) + return HAL_OK; + + assert(hlen + data_len <= der_max); + + /* + * Handle data early, in case it was staged into our output buffer. + */ + memmove(der + hlen, data, data_len); + + if ((err = hal_asn1_encode_header(ASN1_OCTET_STRING, data_len, der, &hlen, der_max)) != HAL_OK) + return err; + + return HAL_OK; +} + +/* * Encode a public key into a X.509 SubjectPublicKeyInfo (RFC 5280). */ @@ -484,6 +566,68 @@ hal_error_t hal_asn1_decode_integer(fp_int *bn, } /* + * Decode an ASN.1 INTEGER into a uint32_t. Since we only + * support (or need to support, or expect to see) unsigned integers, + * we return failure if the sign bit is set in the ASN.1 INTEGER. + */ + +hal_error_t hal_asn1_decode_uint32(uint32_t *np, + const uint8_t * const der, size_t *der_len, const size_t der_max) +{ + if (np == NULL || der == NULL) + return HAL_ERROR_BAD_ARGUMENTS; + + hal_error_t err; + size_t hlen, vlen; + + if ((err = hal_asn1_decode_header(ASN1_INTEGER, der, der_max, &hlen, &vlen)) != HAL_OK) + return err; + + if (der_len != NULL) + *der_len = hlen + vlen; + + if (vlen < 1 || vlen > 5 || (der[hlen] & 0x80) != 0x00 || (vlen == 5 && der[hlen] != 0)) + return HAL_ERROR_ASN1_PARSE_FAILED; + + uint32_t n = 0; + for (size_t i = 0; i < vlen; ++i) { + n <<= 8; // slightly inefficient for the first octet + n += der[hlen + i]; + } + *np = n; + + return HAL_OK; +} + +/* + * Decode an ASN.1 OCTET STRING. + */ + +hal_error_t hal_asn1_decode_octet_string(uint8_t *data, const size_t data_len, + const uint8_t * const der, size_t *der_len, const size_t der_max) +{ + if (der == NULL) + return HAL_ERROR_BAD_ARGUMENTS; + + size_t hlen, vlen; + hal_error_t err; + + if ((err = hal_asn1_decode_header(ASN1_OCTET_STRING, der, der_max, &hlen, &vlen)) != HAL_OK) + return err; + + if (der_len != NULL) + *der_len = hlen + vlen; + + if (data != NULL) { + if (data_len != vlen) + return HAL_ERROR_ASN1_PARSE_FAILED; + memmove(data, der + hlen, vlen); + } + + return HAL_OK; +} + +/* * Decode a public key from a X.509 SubjectPublicKeyInfo (RFC 5280). */ |