[docs] add C and C++ SSL quickstarts

docs/content/latest/quick-start/build-apps/c/ysql.md

@@ -27,6 +27,12 @@ showAsideToc: true
 
 </ul>
 
+{{< tip title="Yugabyte Cloud requires SSL" >}}
+
+Are you using Yugabyte Cloud? Install the [prerequisites](#prerequisites), then go to the [Use C with SSL](#use-c-with-ssl) section.
+
+{{</ tip >}}
+
 ## Prerequisites
 
 The tutorial assumes that you have:
@@ -37,15 +43,15 @@ The tutorial assumes that you have:
 
 ## Install the libpq C driver
 
-The `libpq` C driver is included in the YugabyteDB installation. You can use it by setting the `LD_LIBRARY_PATH` as follows :
-  
+The `libpq` C driver is included in the YugabyteDB installation. You can use it by setting the `LD_LIBRARY_PATH` as follows:
+
 ```sh
 $ export LD_LIBRARY_PATH=<yugabyte-install-dir>/postgres/lib
 ```
 
 Alternatively, you can download the PostgreSQL binaries or build the driver from source as documented [here](https://www.postgresql.org/download/).
 
-## Create the sample C application
+## Create a sample C application
 
 ### Sample C code
 
@@ -158,5 +164,154 @@ You should see the following output:
 ```output
 Created table employee
 Inserted data (1, 'John', 35, 'C')
-Query returned: John 35 C 
+Query returned: John 35 C
+```
+
+## Use C with SSL
+
+The client driver supports several SSL modes, as follows:
+
+| SSL mode | Client driver behavior |
+| :------- | :--------------------- |
+| disable | Supported |
+| allow | Supported |
+| prefer | Supported (default) |
+| require | Supported |
+| verify-ca | Supported |
+| verify-full | Supported |
+
+{{< note title="SSL mode support" >}}
+
+The default SSL mode for libpq is `prefer`. In the `require` SSL mode, the root CA certificate is not required to be configured.
+
+To enable `verify-ca` and `verify-full`, you configure the path to the CA in the connection string using the `sslrootcert` parameter. The default path is `~/.postgresql/root.crt`. If the root certificate is in a different file, specify it in the sslrootcert parameter. For example:
+
+```c
+conninfo = "host=331be4e2-fe24-3d2f-84f0-6d0d49ed422b.cloudportal.yugabyte.com port=5433 dbname=yugabyte user=<username> password=<password> sslmode=verify-full sslrootcert=/Users/yugabyte/Downloads/root.crt"
+```
+
+**Always use verify-full mode if you're using a public CA**. The difference between `verify-ca` and `verify-full` depends on the policy of the root CA. If a you're using a public CA, verify-ca allows connections to a server that somebody else may have registered with the CA. If you're using a local CA, or even a self-signed certificate, using verify-ca often provides enough protection, but using verify-full is always the best security practice.
+
+{{< /note >}}
+
+### Create a sample C application with SSL
+
+Create a file `ybsql_hello_world_ssl.c` and copy the contents below, replacing the hostname, username, and password with the appropriate values:
+
+```c
+#include <stdio.h>
+#include <stdlib.h>
+#include "libpq-fe.h"
+
+int main(int argc, char **argv)
+{
+  const char *conninfo;
+  PGconn     *conn;
+  PGresult   *res;
+  int         nFields;
+  int         i, j;
+
+  /* connection string */
+  /* replace hostname, username, and password */
+  conninfo = "host=hostname port=5433 dbname=yugabyte user=username password=password sslmode=verify-full";
+
+  /* Make a connection to the database */
+  conn = PQconnectdb(conninfo);
+
+  /* Check to see that the backend connection was successfully made */
+  if (PQstatus(conn) != CONNECTION_OK)
+  {
+      fprintf(stderr, "Connection to database failed: %s",
+        PQerrorMessage(conn));
+      PQfinish(conn);
+      exit(1);
+  }
+
+  /* Create table */
+  res = PQexec(conn, "CREATE TABLE employee (id int PRIMARY KEY, \
+                                             name varchar, age int, \
+                                             language varchar)");
+
+  if (PQresultStatus(res) != PGRES_COMMAND_OK)
+  {
+      fprintf(stderr, "CREATE TABLE failed: %s", PQerrorMessage(conn));
+      PQclear(res);
+      PQfinish(conn);
+      exit(1);
+  }
+  PQclear(res);
+  printf("Created table employee\n");
+
+  /* Insert a row */
+  res = PQexec(conn, "INSERT INTO employee (id, name, age, language) \
+                      VALUES (1, 'John', 35, 'C')");
+
+  if (PQresultStatus(res) != PGRES_COMMAND_OK)
+  {
+      fprintf(stderr, "INSERT failed: %s", PQerrorMessage(conn));
+      PQclear(res);
+      PQfinish(conn);
+      exit(1);
+  }
+  PQclear(res);
+  printf("Inserted data (1, 'John', 35, 'C')\n");
+
+  /* Query the row */
+  res = PQexec(conn, "SELECT name, age, language FROM employee WHERE id = 1");
+  if (PQresultStatus(res) != PGRES_TUPLES_OK)
+  {
+      fprintf(stderr, "SELECT failed: %s", PQerrorMessage(conn));
+      PQclear(res);
+      PQfinish(conn);
+      exit(1);
+  }
+
+  /* print out the rows */
+  nFields = PQnfields(res);
+  for (i = 0; i < PQntuples(res); i++)
+  {
+      printf("Query returned: ");
+      for (j = 0; j < nFields; j++)
+        printf("%s ", PQgetvalue(res, i, j));
+      printf("\n");
+  }
+  PQclear(res);
+
+  /* close the connection to the database and cleanup */
+  PQfinish(conn);
+
+  return 0;
+}
+```
+
+### Run the C SSL application
+
+1. Set up your environment, replacing `<yb-install-path>` with the full path to your YugabyteDB installation:
+
+    ```sh
+    $ export LD_LIBRARY_PATH=<yb-install-path>/postgres/include/
+    $ export DYLD_LIBRARY_PATH=<yb-install-path>/postgres/lib/
+    ```
+
+1. You can compile the file using `gcc` or `clang`. To compile the application with `clang`, run the following command:
+
+    ```sh
+    $ clang yb_hello_world_ssl.c \
+        -lpq \
+        -I path/to/yugabytedb/postgres/include -L path/to/yugabytedb/postgres/postgres/lib \
+        -o ybsql_hello_world_ssl
+    ```
+
+1. Run with:
+
+    ```sh
+    $ ./ybsql_hello_world
+    ```
+
+You should see the following output:
+
+```output
+Created table employee
+Inserted data (1, 'John', 35, 'C')
+Query returned: John 35 C
 ```