SocketWrapper: implement SSLClient

connect() temporarily accepts a third parameter with a PEM encoded certificate

Cleanest way to add it is via raw strings

const char * certificate = R"(-----BEGIN CERTIFICATE-----
....
-----END CERTIFICATE-----)";

Author: facchinm

Diff for: libraries/SocketWrapper/SocketWrapper.h

@@ -1,10 +1,18 @@
 #pragma once
 
+#include "zephyr/sys/printk.h"
+#if defined(CONFIG_NET_SOCKETS_SOCKOPT_TLS)
+#include <zephyr/net/tls_credentials.h>
+#define CA_CERTIFICATE_TAG 1
+#endif
+
 #include <zephyr/net/socket.h>
 
 class ZephyrSocketWrapper {
 protected:
     int sock_fd;
+    bool is_ssl = false;
+    int ssl_sock_temp_char = -1;
 
 public:
     ZephyrSocketWrapper() : sock_fd(-1) {}
@@ -33,6 +41,8 @@ class ZephyrSocketWrapper {
 
             if (ret == 0) {
                 break;
+            } else {
+                k_sleep(K_MSEC(1));
             }
         }
 
@@ -77,11 +87,86 @@ class ZephyrSocketWrapper {
         return true;
     }
 
+#if defined(CONFIG_NET_SOCKETS_SOCKOPT_TLS)
+    bool connectSSL(const char* host, uint16_t port, char* ca_certificate_pem = nullptr) {
+
+        // Resolve address
+        struct addrinfo hints;
+        struct addrinfo *res;
+
+        hints.ai_family = AF_INET;
+        hints.ai_socktype = SOCK_STREAM;
+
+        int resolve_attempts = 100;
+        int ret;
+
+	    while (resolve_attempts--) {
+            ret = getaddrinfo(host, String(port).c_str(), &hints, &res);
+
+            if (ret == 0) {
+                break;
+            } else {
+                k_sleep(K_MSEC(1));
+            }
+        }
+
+	    if (ret != 0) {
+            return false;
+        }
+
+        if (ca_certificate_pem != nullptr) {
+            ret = tls_credential_add(CA_CERTIFICATE_TAG, TLS_CREDENTIAL_CA_CERTIFICATE,
+                ca_certificate_pem, strlen(ca_certificate_pem) + 1);
+            Serial.println(ret);
+        }
+
+        sock_fd = socket(AF_INET, SOCK_STREAM, IPPROTO_TLS_1_2);
+        if (sock_fd < 0) {
+            return false;
+        }
+
+        sec_tag_t sec_tag_opt[] = {
+            CA_CERTIFICATE_TAG,
+        };
+        setsockopt(sock_fd, SOL_TLS, TLS_SEC_TAG_LIST,
+                sec_tag_opt, sizeof(sec_tag_opt));
+
+        setsockopt(sock_fd, SOL_TLS, TLS_HOSTNAME, host, strlen(host));
+
+        uint32_t timeo_optval = 100;
+        setsockopt(sock_fd, SOL_SOCKET, SO_RCVTIMEO, &timeo_optval, sizeof(timeo_optval));
+
+        if (::connect(sock_fd, res->ai_addr, res->ai_addrlen) < 0) {
+            ::close(sock_fd);
+            sock_fd = -1;
+            return false;
+        }
+        is_ssl = true;
+
+        return true;
+    }
+#endif
+
     int available() {
         int count = 0;
-        zsock_ioctl(sock_fd, ZFD_IOCTL_FIONREAD, &count);
-        if (count == 0) {
+        if (is_ssl) {
+        /*
+            TODO: HACK:
+            The correct colution would be to call
+            ::recv(sock_fd, &ssl_sock_temp_char, 1, MSG_PEEK | MSG_DONTWAIT);
+            but it doesn't seem to work. Instead, save a temporary variable
+            and use it in read()
+        */
+            if (ssl_sock_temp_char != -1) {
+                return 1;
+            }
+            count = ::recv(sock_fd, &ssl_sock_temp_char, 1, MSG_DONTWAIT);
+        } else {
+            zsock_ioctl(sock_fd, ZFD_IOCTL_FIONREAD, &count);
+        }
+        if (count <= 0) {
             delay(1);
+            count = 0;
         }
         return count;
     }
@@ -90,6 +175,13 @@ class ZephyrSocketWrapper {
         if (sock_fd == -1) {
             return -1;
         }
+        // TODO: see available()
+        if (ssl_sock_temp_char != -1) {
+            int ret = ::recv(sock_fd, &buffer[1], size - 1, flags);
+            buffer[0] = ssl_sock_temp_char;
+            ssl_sock_temp_char = -1;
+            return ret + 1;
+        }
         return ::recv(sock_fd, buffer, size, flags);
     }
 

Diff for: libraries/SocketWrapper/ZephyrClient.h

@@ -28,6 +28,18 @@ class ZephyrClient : public arduino::Client, ZephyrSocketWrapper {
         }
         return ret;
     }
+#if defined(CONFIG_NET_SOCKETS_SOCKOPT_TLS)
+    int connectSSL(const char* host, uint16_t port, const char* cert) {
+        return this->connectSSL(host, port, (char*)cert);
+    }
+    int connectSSL(const char* host, uint16_t port, char* cert) {
+        auto ret = ZephyrSocketWrapper::connectSSL((char*)host, port, cert);
+        if (ret) {
+            _connected = true;
+        }
+        return ret;
+    }
+#endif
     uint8_t connected() override {
         return _connected;
     }

Diff for: libraries/SocketWrapper/ZephyrSSLClient.h

@@ -0,0 +1,18 @@
+#include "SocketWrapper.h"
+#include "api/Client.h"
+#include "unistd.h"
+#include "zephyr/sys/printk.h"
+#include "ZephyrClient.h"
+
+#if defined(CONFIG_NET_SOCKETS_SOCKOPT_TLS)
+class ZephyrSSLClient : public ZephyrClient {
+
+public:
+    int connect(const char* host, uint16_t port, const char* cert) {
+        return connectSSL(host, port, (char*)cert);
+    }
+    int connect(const char* host, uint16_t port, char* cert) {
+        return connectSSL(host, port, cert);
+    }
+};
+#endif