internal static string FindHttpAiaRecord(byte[] authorityInformationAccess, string recordTypeOid)
{
DerSequenceReader reader = new DerSequenceReader(authorityInformationAccess);
while (reader.HasData)
{
DerSequenceReader innerReader = reader.ReadSequence();
// If the sequence's first element is a sequence, unwrap it.
if (innerReader.PeekTag() == ConstructedSequenceTagId)
{
innerReader = innerReader.ReadSequence();
}
Oid oid = innerReader.ReadOid();
if (StringComparer.Ordinal.Equals(oid.Value, recordTypeOid))
{
string uri = innerReader.ReadIA5String();
Uri parsedUri;
if (!Uri.TryCreate(uri, UriKind.Absolute, out parsedUri))
{
continue;
}
if (!StringComparer.Ordinal.Equals(parsedUri.Scheme, "http"))
{
continue;
}
return(uri);
}
}
return(null);
}
private static string FindAltNameMatch(byte[] extensionBytes, GeneralNameType matchType, string otherOid)
{
// If Other, have OID, else, no OID.
Debug.Assert(
(otherOid == null) == (matchType != GeneralNameType.OtherName),
$"otherOid has incorrect nullarity for matchType {matchType}");
Debug.Assert(
matchType == GeneralNameType.UniformResourceIdentifier ||
matchType == GeneralNameType.DnsName ||
matchType == GeneralNameType.Email ||
matchType == GeneralNameType.OtherName,
$"matchType ({matchType}) is not currently supported");
Debug.Assert(
otherOid == null || otherOid == Oids.UserPrincipalName,
$"otherOid ({otherOid}) is not supported");
// SubjectAltName ::= GeneralNames
//
// IssuerAltName ::= GeneralNames
//
// GeneralNames ::= SEQUENCE SIZE (1..MAX) OF GeneralName
//
// GeneralName ::= CHOICE {
// otherName [0] OtherName,
// rfc822Name [1] IA5String,
// dNSName [2] IA5String,
// x400Address [3] ORAddress,
// directoryName [4] Name,
// ediPartyName [5] EDIPartyName,
// uniformResourceIdentifier [6] IA5String,
// iPAddress [7] OCTET STRING,
// registeredID [8] OBJECT IDENTIFIER }
//
// OtherName::= SEQUENCE {
// type - id OBJECT IDENTIFIER,
// value[0] EXPLICIT ANY DEFINED BY type - id }
byte expectedTag = (byte)(DerSequenceReader.ContextSpecificTagFlag | (byte)matchType);
if (matchType == GeneralNameType.OtherName)
{
expectedTag |= DerSequenceReader.ConstructedFlag;
}
DerSequenceReader altNameReader = new DerSequenceReader(extensionBytes);
while (altNameReader.HasData)
{
if (altNameReader.PeekTag() != expectedTag)
{
altNameReader.SkipValue();
continue;
}
switch (matchType)
{
case GeneralNameType.OtherName:
{
DerSequenceReader otherNameReader = altNameReader.ReadSequence();
string oid = otherNameReader.ReadOidAsString();
if (oid == otherOid)
{
// Payload is value[0] EXPLICIT, meaning
// a) it'll be tagged as ContextSpecific0
// b) that's interpretable as a Sequence (EXPLICIT)
// c) the payload will then be retagged as the correct type (EXPLICIT)
if (otherNameReader.PeekTag() != DerSequenceReader.ContextSpecificConstructedTag0)
{
throw new CryptographicException(SR.Cryptography_Der_Invalid_Encoding);
}
otherNameReader = otherNameReader.ReadSequence();
// Currently only UPN is supported, which is a UTF8 string per
// https://msdn.microsoft.com/en-us/library/ff842518.aspx
return(otherNameReader.ReadUtf8String());
}
// If the OtherName OID didn't match, move to the next entry.
continue;
}
case GeneralNameType.Rfc822Name:
case GeneralNameType.DnsName:
case GeneralNameType.UniformResourceIdentifier:
return(altNameReader.ReadIA5String());
default:
altNameReader.SkipValue();
continue;
}
}
return(null);
}
private static string GetCdpUrl(X509Certificate2 cert)
{
byte[] crlDistributionPoints = null;
foreach (X509Extension extension in cert.Extensions)
{
if (StringComparer.Ordinal.Equals(extension.Oid.Value, Oids.CrlDistributionPoints))
{
// If there's an Authority Information Access extension, it might be used for
// looking up additional certificates for the chain.
crlDistributionPoints = extension.RawData;
break;
}
}
if (crlDistributionPoints == null)
{
return(null);
}
// CRLDistributionPoints ::= SEQUENCE SIZE (1..MAX) OF DistributionPoint
//
// DistributionPoint ::= SEQUENCE {
// distributionPoint [0] DistributionPointName OPTIONAL,
// reasons [1] ReasonFlags OPTIONAL,
// cRLIssuer [2] GeneralNames OPTIONAL }
//
// DistributionPointName ::= CHOICE {
// fullName [0] GeneralNames,
// nameRelativeToCRLIssuer [1] RelativeDistinguishedName }
//
// GeneralNames ::= SEQUENCE SIZE (1..MAX) OF GeneralName
//
// GeneralName ::= CHOICE {
// otherName [0] OtherName,
// rfc822Name [1] IA5String,
// dNSName [2] IA5String,
// x400Address [3] ORAddress,
// directoryName [4] Name,
// ediPartyName [5] EDIPartyName,
// uniformResourceIdentifier [6] IA5String,
// iPAddress [7] OCTET STRING,
// registeredID [8] OBJECT IDENTIFIER }
DerSequenceReader cdpSequence = new DerSequenceReader(crlDistributionPoints);
while (cdpSequence.HasData)
{
const byte ContextSpecificFlag = 0x80;
const byte ContextSpecific0 = ContextSpecificFlag;
const byte ConstructedFlag = 0x20;
const byte ContextSpecificConstructed0 = ContextSpecific0 | ConstructedFlag;
const byte GeneralNameUri = ContextSpecificFlag | 0x06;
DerSequenceReader distributionPointReader = cdpSequence.ReadSequence();
byte tag = distributionPointReader.PeekTag();
// Only distributionPoint is supported
if (tag != ContextSpecificConstructed0)
{
continue;
}
// The DistributionPointName is a CHOICE, not a SEQUENCE, but the reader is the same.
DerSequenceReader dpNameReader = distributionPointReader.ReadSequence();
tag = dpNameReader.PeekTag();
// Only fullName is supported,
// nameRelativeToCRLIssuer is for LDAP-based lookup.
if (tag != ContextSpecificConstructed0)
{
continue;
}
DerSequenceReader fullNameReader = dpNameReader.ReadSequence();
while (fullNameReader.HasData)
{
tag = fullNameReader.PeekTag();
if (tag != GeneralNameUri)
{
fullNameReader.SkipValue();
continue;
}
string uri = fullNameReader.ReadIA5String();
Uri parsedUri = new Uri(uri);
if (!StringComparer.Ordinal.Equals(parsedUri.Scheme, "http"))
{
continue;
}
return(uri);
}
}
return(null);
}