fix(s2nd): parse psk given to s2nd non-destructively (aws#4006)

* fix: use stuffer for psk params

* specify precision when printing the psk identity

* fix formatting

* cast token pointer

* Copy the string instead of using stuffer

* Remove empty line

* remove empty line

* fix comment format

bin/common.c

@@ -263,8 +263,13 @@ static int s2n_setup_external_psk(struct s2n_psk **psk, char *params)
     GUARD_EXIT_NULL(psk);
     GUARD_EXIT_NULL(params);
 
+    /* duplicate params as strtok will modify the input string */
+    char *params_dup = malloc(strlen(params) + 1);
+    GUARD_EXIT_NULL(params_dup);
+    strcpy(params_dup, params);
+
     size_t token_idx = 0;
-    for (char *token = strtok(params, ","); token != NULL; token = strtok(NULL, ","), token_idx++) {
+    for (char *token = strtok(params_dup, ","); token != NULL; token = strtok(NULL, ","), token_idx++) {
         switch (token_idx) {
             case 0:
                 GUARD_EXIT(s2n_psk_set_identity(*psk, (const uint8_t *) token, strlen(token)),
@@ -288,6 +293,7 @@ static int s2n_setup_external_psk(struct s2n_psk **psk, char *params)
         }
     }
 
+    free(params_dup);
     return S2N_SUCCESS;
 }
 

bin/echo.c

@@ -213,7 +213,7 @@ int print_connection_info(struct s2n_connection *conn)
         uint8_t *identity = (uint8_t *) malloc(identity_length);
         GUARD_EXIT_NULL(identity);
         GUARD_EXIT(s2n_connection_get_negotiated_psk_identity(conn, identity, identity_length), "Error getting negotiated psk identity from the connection\n");
-        printf("Negotiated PSK identity: %s\n", identity);
+        printf("Negotiated PSK identity: %.*s\n", identity_length, identity);
         free(identity);
     }