1 files changed, 58 insertions, 0 deletions
diff --git a/lib/mbedtls_errors/tester.c b/lib/mbedtls_errors/tester.c
new file mode 100644
index 0000000000..6f1c788f50
--- /dev/null
+++ b/lib/mbedtls_errors/tester.c
@@ -0,0 +1,58 @@
+#include "mbedtls/error.h"
+#include <string.h>
+#include <stdio.h>
+
+// test_code checks that the provided code results in the provided error string for any size
+// buffer. It calls mbedtls_strerror() to fill a buffer that is from 1 to 100 bytes in length
+// and then checks that the buffer contents is OK and that a few guard bytes before and after
+// the buffer were not overwritten.
+int test_code(int code, char *str) {
+    char buf[100];
+    int ok = 1;
+    int res;
+
+    // test zero-length buffer
+    memset(buf, -3, 100);
+    mbedtls_strerror(code, buf + 4, 0);
+    for (int i = 0; i < 10; i++) {
+        if (buf[i] != -3) {
+            printf("Error: guard overwritten buflen=0 i=%d buf[i]=%d\n", i, buf[i]);
+            ok = 0;
+        }
+    }
+
+    // test
+    for (size_t buflen = 1; buflen < 90; buflen++) {
+        memset(buf, -3, 100);
+        mbedtls_strerror(code, buf + 4, buflen);
+        for (int i = 0; i < 4; i++) {
+            if (buf[i] != -3) {
+                printf("Error: pre-guard overwritten buflen=%d i=%d buf[i]=%d\n", buflen, i, buf[i]);
+                ok = 0;
+            }
+        }
+        for (int i = 4 + buflen; i < 100; i++) {
+            if (buf[i] != -3) {
+                printf("Error: post-guard overwritten buflen=%d i=%d buf[i]=%d\n", buflen, i, buf[i]);
+                ok = 0;
+            }
+        }
+        char exp[100];
+        strncpy(exp, str, buflen);
+        exp[buflen - 1] = 0;
+        if (strcmp(buf + 4, exp) != 0) {
+            printf("Error: expected %s, got %s\n", exp, buf);
+            ok = 0;
+        }
+    }
+
+    printf("Test %x -> %s is %s\n", code, str, ok?"OK":"*** BAD ***");
+}
+
+int main() {
+    test_code(0x7200, "MBEDTLS_ERR_SSL_INVALID_RECORD");
+    test_code(0x7780, "MBEDTLS_ERR_SSL_FATAL_ALERT_MESSAGE");
+    test_code(0x0074, "MBEDTLS_ERR_SHA256_BAD_INPUT_DATA");
+    test_code(0x6600 | 0x0074, "MBEDTLS_ERR_SSL_INVALID_VERIFY_HASH+MBEDTLS_ERR_SHA256_BAD_INPUT_DATA");
+    test_code(103, "MBEDTLS_ERR_UNKNOWN (0x0067)");
+}