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Add content validation for ASN.1 timestamps #6

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Merged
mdehoog merged 1 commit into from
Jan 11, 2025
Merged

Add content validation for ASN.1 timestamps #6

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12 changes: 11 additions & 1 deletion src/Asn1Decode.sol
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Original file line number Diff line number Diff line change
Expand Up @@ -178,10 +178,20 @@ library Asn1Decode {
* @return UNIX timestamp (seconds since 1970/01/01)
*/
function timestampAt(bytes memory der, Asn1Ptr ptr) internal pure returns (uint256) {
uint16 _years;
uint8 _type = uint8(der[ptr.header()]);
uint256 offset = ptr.content();
uint256 length = ptr.length();

// content validation:
require((_type == 0x17 && length == 13) || (_type == 0x18 && length == 15), "Invalid TIMESTAMP");
require(der[offset + length - 1] == 0x5A, "TIMESTAMP must be UTC"); // 0x5A == 'Z'
for (uint256 i = 0; i < length - 1; i++) {
// all other characters must be digits between 0 and 9
uint8 v = uint8(der[offset + i]);
require(48 <= v && v <= 57, "Invalid character in TIMESTAMP");
}

uint16 _years;
if (length == 13) {
_years = (uint8(der[offset]) - 48 < 5) ? 2000 : 1900;
} else {
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