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asn: refactoring EccPrivateKeyDecode to reduce stack usage (199 bytes - pointer sizes saved):

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--- variable priv moved to the heap (66 bytes saved)
--- variable pub moved to the heap (133 bytes saved)
This commit is contained in:
Moisés Guimarães
2014-07-04 12:03:56 -03:00
parent 2913aa89d4
commit b7acbc090f
1 changed files with 71 additions and 42 deletions
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113
ctaocrypt/src/asn.c
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@ -6296,8 +6296,10 @@ int EccPrivateKeyDecode(const byte* input, word32* inOutIdx, ecc_key* key,
int version, length;
int privSz, pubSz;
byte b;
byte priv[ECC_MAXSIZE];
byte pub[ECC_MAXSIZE * 2 + 1]; /* public key has two parts plus header */
int ret = 0;
DECLARE_ARRAY(byte, priv, ECC_MAXSIZE);
DECLARE_ARRAY(byte, pub, ECC_MAXSIZE * 2 + 1); /* public key has two parts
plus header */
if (input == NULL || inOutIdx == NULL || key == NULL || inSz == 0)
return BAD_FUNC_ARG;
@ -6319,6 +6321,9 @@ int EccPrivateKeyDecode(const byte* input, word32* inOutIdx, ecc_key* key,
return ASN_PARSE_E;
/* priv key */
if (!CREATE_ARRAY(byte, priv, ECC_MAXSIZE))
return MEMORY_E;
privSz = length;
XMEMCPY(priv, &input[*inOutIdx], privSz);
*inOutIdx += length;
@ -6329,54 +6334,78 @@ int EccPrivateKeyDecode(const byte* input, word32* inOutIdx, ecc_key* key,
*inOutIdx += 1;
if (GetLength(input, inOutIdx, &length, inSz) < 0)
return ASN_PARSE_E;
ret = ASN_PARSE_E;
else {
/* object id */
b = input[*inOutIdx];
*inOutIdx += 1;
/* object id */
if (b != ASN_OBJECT_ID) {
ret = ASN_OBJECT_ID_E;
}
else if (GetLength(input, inOutIdx, &length, inSz) < 0) {
ret = ASN_PARSE_E;
}
else {
while(length--) {
oid += input[*inOutIdx];
*inOutIdx += 1;
}
if (CheckCurve(oid) < 0)
ret = ECC_CURVE_OID_E;
}
}
}
if (ret == 0) {
/* prefix 1 */
b = input[*inOutIdx];
*inOutIdx += 1;
if (b != ASN_OBJECT_ID)
return ASN_OBJECT_ID_E;
if (GetLength(input, inOutIdx, &length, inSz) < 0)
return ASN_PARSE_E;
while(length--) {
oid += input[*inOutIdx];
*inOutIdx += 1;
if (b != ECC_PREFIX_1) {
ret = ASN_ECC_KEY_E;
}
else if (GetLength(input, inOutIdx, &length, inSz) < 0) {
ret = ASN_PARSE_E;
}
else {
/* key header */
b = input[*inOutIdx];
*inOutIdx += 1;
if (b != ASN_BIT_STRING) {
ret = ASN_BITSTR_E;
}
else if (GetLength(input, inOutIdx, &length, inSz) < 0) {
ret = ASN_PARSE_E;
}
else {
b = input[*inOutIdx];
*inOutIdx += 1;
if (b != 0x00) {
ret = ASN_EXPECT_0_E;
}
else if (!CREATE_ARRAY(byte, pub, ECC_MAXSIZE * 2 + 1))
ret = MEMORY_E;
else {
/* pub key */
pubSz = length - 1; /* null prefix */
XMEMCPY(pub, &input[*inOutIdx], pubSz);
*inOutIdx += length;
ret = ecc_import_private_key(priv, privSz, pub, pubSz, key);
DESTROY_ARRAY(pub);
}
}
}
if (CheckCurve(oid) < 0)
return ECC_CURVE_OID_E;
}
/* prefix 1 */
b = input[*inOutIdx];
*inOutIdx += 1;
if (b != ECC_PREFIX_1)
return ASN_ECC_KEY_E;
if (GetLength(input, inOutIdx, &length, inSz) < 0)
return ASN_PARSE_E;
DESTROY_ARRAY(priv);
/* key header */
b = input[*inOutIdx];
*inOutIdx += 1;
if (b != ASN_BIT_STRING)
return ASN_BITSTR_E;
if (GetLength(input, inOutIdx, &length, inSz) < 0)
return ASN_PARSE_E;
b = input[*inOutIdx];
*inOutIdx += 1;
if (b != 0x00)
return ASN_EXPECT_0_E;
pubSz = length - 1; /* null prefix */
XMEMCPY(pub, &input[*inOutIdx], pubSz);
*inOutIdx += length;
return ecc_import_private_key(priv, privSz, pub, pubSz, key);
return ret;
}
#endif /* HAVE_ECC */