tls: process incoming client hello
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@ -27,6 +27,7 @@ use smoltcp_tls::key::*;
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use smoltcp_tls::buffer::TlsBuffer;
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use smoltcp_tls::certificate::*;
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use smoltcp_tls::parse::*;
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use smoltcp_tls::TlsRng;
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struct CountingRng(u64);
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@ -51,6 +52,8 @@ impl RngCore for CountingRng {
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impl CryptoRng for CountingRng {}
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impl TlsRng for CountingRng {}
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static mut RNG: CountingRng = CountingRng(0);
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fn main() {
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@ -72,7 +75,7 @@ fn main() {
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)
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};
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tls_socket.tcp_connect(
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tls_socket.connect(
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&mut sockets,
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(Ipv4Address::new(192, 168, 1, 125), 1883),
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49600
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181
src/tls.rs
181
src/tls.rs
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@ -915,6 +915,187 @@ impl<'s> TlsSocket<'s> {
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todo!()
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}
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// Process as Client Hello
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if let HandshakeData::ClientHello(client_hello)
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= might_be_client_hello.handshake_data
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{
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// Checks on the client hello structure
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// Read session ID
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// Select acceptable TLS 1.3 cipher suite
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let session_id = client_hello.session_id;
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let accepted_cipher_suite = {
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let recognized_cipher_suite = client_hello.cipher_suites
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.iter()
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.find(|cipher_suite| {
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// CCM_8 is the only unsupported cipher suite
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if let Some(cipher) = cipher_suite {
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cipher != &CipherSuite::TLS_AES_128_CCM_8_SHA256
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} else {
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false
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}
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});
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if let Some(Some(nominated_cipher_suite)) = recognized_cipher_suite {
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nominated_cipher_suite
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} else {
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// Not appropriate cipher found
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// Send alert
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todo!()
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}
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};
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// Check on the handshakes
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// `supported_version` extension: only support TLS 1.3 (SSL 3.4)
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// `supported_groups` extension: select an acceptable ECDHE group
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// `key_share` extension: find the corresponding ECDHE shared key
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// `signature_algorithm`: pick a signature algorithm
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// Will not handle PSK, no 0-RTT
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let mut version_check = false;
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let mut offered_p256 = false;
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let mut offered_x25519 = false;
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let mut p256_public_key: Option<p256::EncodedPoint> = None;
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let mut x25519_public_key: Option<x25519_dalek::PublicKey> = None;
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let mut signature_schemes: Vec<SignatureScheme> = Vec::new();
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// Verify that TLS 1.3 is offered by the client
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if let Some(supported_version_extension) = client_hello.extensions.iter().find(
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|extension| extension.extension_type == ExtensionType::SupportedVersions
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) {
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if let ExtensionData::SupportedVersions(supported_version)
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= &supported_version_extension.extension_data
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{
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if let SupportedVersions::ClientHello { versions, .. }
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= supported_version
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{
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version_check = true;
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if versions.iter().find(
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|&&version| version == TlsVersion::Tls13
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).is_none()
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{
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// TLS 1.3 was not offered by client
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// Reject connection immediately
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todo!()
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}
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} else {
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// Wrong variant appeared, probably malformed
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todo!()
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}
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} else {
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// Malformed TLS packet
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todo!()
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}
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} else {
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// No supported_version extension was found,
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// Terminate by sending alert
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todo!()
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}
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// Check offered ECDHE algorithm
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if let Some(supported_groups) = client_hello.extensions.iter().find(
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|extension| extension.extension_type == ExtensionType::SupportedGroups
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) {
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if let ExtensionData::NegotiatedGroups(NamedGroupList { named_group_list, .. })
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= &supported_groups.extension_data
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{
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// Mark down the offered and acceptable group
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if let Some(group) = named_group_list.iter().find(
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|&&named_group| {
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named_group == NamedGroup::secp256r1
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}
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) {
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offered_p256 = true;
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}
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if let Some(group) = named_group_list.iter().find(
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|&&named_group| {
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named_group == NamedGroup::x25519
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}
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) {
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offered_x25519 = true;
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}
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} else {
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// Malformed TLS packet
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todo!()
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}
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} else {
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// Client did not offer ECDHE algorithm
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todo!()
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}
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// Select usable key
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if let Some(key_shares) = client_hello.extensions.iter().find(
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|extension| extension.extension_type == ExtensionType::KeyShare
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) {
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if let ExtensionData::KeyShareEntry(
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KeyShareEntryContent::KeyShareClientHello { client_shares, .. }
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) = &key_shares.extension_data {
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// Try P-256 first, if offered by client
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if offered_p256 {
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if let Some(p256_key) = client_shares.iter().find(
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|key| {
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key.group == NamedGroup::secp256r1
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}
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) {
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p256_public_key.replace(
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p256::EncodedPoint::from_untagged_bytes(
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GenericArray::from_slice(
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&p256_key.key_exchange[1..]
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)
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)
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);
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}
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}
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// Then try X25519, if P-256 key is not found and x25519 is offered
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if offered_x25519 && p256_public_key.is_none() {
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if let Some(x25519_key) = client_shares.iter().find(
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|key| {
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key.group == NamedGroup::x25519
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}
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) {
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// Prepare a 32-bytes buffer for the public key
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let mut key_content: [u8; 32] = [0; 32];
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key_content.clone_from_slice(&x25519_key.key_exchange);
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x25519_public_key.replace(
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x25519_dalek::PublicKey::from(
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key_content
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)
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);
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}
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}
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// If there are no applicable offered client key,
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// consider sending a ClientHelloRetry
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if p256_public_key.is_none() && x25519_public_key.is_none() {
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todo!()
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}
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} else {
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// Malformed packet
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// Send alert to client
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todo!()
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}
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} else {
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// The key_share extension was not sent
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// Consider sending a ClientHelloRequest
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todo!()
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}
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// Select signature algorithm
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if let Some(signature_algorithms) = client_hello.extensions.iter().find(
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|extension| extension.extension_type == ExtensionType::SignatureAlgorithms
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) {
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if let ExtensionData::SignatureAlgorithms(
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SignatureSchemeList { supported_signature_algorithms, .. }
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) = &signature_algorithms.extension_data {
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signature_schemes.extend_from_slice(supported_signature_algorithms);
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}
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} else {
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// Will only accept authentication through certificate
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// Send alert if there are no signature algorithms extension
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todo!()
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}
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}
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log::info!("Received client hello");
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}
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