diff options
| -rw-r--r-- | crypto/src/tls/AbstractTlsServer.cs | 56 |
1 files changed, 46 insertions, 10 deletions
diff --git a/crypto/src/tls/AbstractTlsServer.cs b/crypto/src/tls/AbstractTlsServer.cs index 7e8c26ffd..16b2af15e 100644 --- a/crypto/src/tls/AbstractTlsServer.cs +++ b/crypto/src/tls/AbstractTlsServer.cs @@ -67,6 +67,16 @@ namespace Org.BouncyCastle.Tls return "No selectable cipher suite"; } + protected virtual int GetMaximumDefaultCurveBits() + { + return NamedGroup.GetCurveBits(NamedGroup.secp521r1); + } + + protected virtual int GetMaximumDefaultFiniteFieldBits() + { + return NamedGroup.GetFiniteFieldBits(NamedGroup.ffdhe8192); + } + protected virtual int GetMaximumNegotiableCurveBits() { int maxBits = 0; @@ -85,7 +95,7 @@ namespace Org.BouncyCastle.Tls * extensions. In this case, the server is free to choose any one of the elliptic curves or point * formats [...]. */ - maxBits = NamedGroup.GetMaximumCurveBits(); + maxBits = GetMaximumDefaultCurveBits(); } return maxBits; } @@ -110,7 +120,7 @@ namespace Org.BouncyCastle.Tls * entirely or contains no FFDHE groups (i.e., no codepoints between 256 and 511, inclusive), then * the server [...] MAY select an FFDHE cipher suite and offer an FFDHE group of its choice [...]. */ - maxBits = NamedGroup.GetMaximumFiniteFieldBits(); + maxBits = GetMaximumDefaultFiniteFieldBits(); } return maxBits; } @@ -142,23 +152,39 @@ namespace Org.BouncyCastle.Tls return true; } + // TODO[api] Preferably return TlsDHConfig from here to support custom DH groups more easily protected virtual int SelectDH(int minimumFiniteFieldBits) { + bool anyPeerFF = false; int[] clientSupportedGroups = m_context.SecurityParameters.ClientSupportedGroups; - if (clientSupportedGroups == null) - return SelectDHDefault(minimumFiniteFieldBits); + if (clientSupportedGroups != null) + { + // Try to find a supported named group of the required size from the client's list. + for (int i = 0; i < clientSupportedGroups.Length; ++i) + { + int namedGroup = clientSupportedGroups[i]; + anyPeerFF |= NamedGroup.IsFiniteField(namedGroup); - // Try to find a supported named group of the required size from the client's list. - for (int i = 0; i < clientSupportedGroups.Length; ++i) + if (NamedGroup.GetFiniteFieldBits(namedGroup) >= minimumFiniteFieldBits) + { + // This default server implementation supports all NamedGroup finite fields + return namedGroup; + } + } + } + if (!anyPeerFF) { - int namedGroup = clientSupportedGroups[i]; - if (NamedGroup.GetFiniteFieldBits(namedGroup) >= minimumFiniteFieldBits) - return namedGroup; + /* + * RFC 7919 4. If [...] the Supported Groups extension is either absent from the ClientHello + * entirely or contains no FFDHE groups (i.e., no codepoints between 256 and 511, inclusive), then + * the server [...] MAY select an FFDHE cipher suite and offer an FFDHE group of its choice [...]. + */ + return SelectDHDefault(minimumFiniteFieldBits); } - return -1; } + // TODO[api] Preferably return TlsDHConfig from here to support custom DH groups more easily protected virtual int SelectDHDefault(int minimumFiniteFieldBits) { return minimumFiniteFieldBits <= 2048 ? NamedGroup.ffdhe2048 @@ -173,14 +199,24 @@ namespace Org.BouncyCastle.Tls { int[] clientSupportedGroups = m_context.SecurityParameters.ClientSupportedGroups; if (clientSupportedGroups == null) + { + /* + * RFC 4492 4. A client that proposes ECC cipher suites may choose not to include these + * extensions. In this case, the server is free to choose any one of the elliptic curves or point + * formats [...]. + */ return SelectECDHDefault(minimumCurveBits); + } // Try to find a supported named group of the required size from the client's list. for (int i = 0; i < clientSupportedGroups.Length; ++i) { int namedGroup = clientSupportedGroups[i]; if (NamedGroup.GetCurveBits(namedGroup) >= minimumCurveBits) + { + // This default server implementation supports all NamedGroup curves return namedGroup; + } } return -1; |