util: add base64 decoding function

The standard glib provided g_base64_decode doesn't provide any
kind of sensible error checking on its input. Add a QEMU custom
wrapper qbase64_decode which can be used with untrustworthy
input that can contain invalid base64 characters, embedded
NUL characters, or not be NUL terminated at all.

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

1 files changed, 109 insertions, 0 deletions

diff --git a/tests/test-base64.c b/tests/test-base64.c
new file mode 100644
index 0000000000..a0ca2d8de8
--- /dev/null
+++ b/tests/test-base64.c
@@ -0,0 +1,109 @@
+/*
+ * QEMU base64 helper test
+ *
+ * Copyright (c) 2015 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include <glib.h>
+
+#include "qemu/base64.h"
+
+
+static void test_base64_good(void)
+{
+    const char input[] =
+        "QmVjYXVzZSB3ZSBmb2N1c2VkIG9uIHRoZSBzbmFrZSwgd2UgbW\n"
+        "lzc2VkIHRoZSBzY29ycGlvbi4=";
+    const char expect[] = "Because we focused on the snake, "
+        "we missed the scorpion.";
+
+    size_t len;
+    uint8_t *actual = qbase64_decode(input,
+                                     -1,
+                                     &len,
+                                     &error_abort);
+
+    g_assert(actual != NULL);
+    g_assert_cmpint(len, ==, strlen(expect));
+    g_assert_cmpstr((char *)actual, ==, expect);
+    g_free(actual);
+}
+
+
+static void test_base64_bad(const char *input,
+                            size_t input_len)
+{
+    size_t len;
+    Error *err = NULL;
+    uint8_t *actual = qbase64_decode(input,
+                                     input_len,
+                                     &len,
+                                     &err);
+
+    g_assert(err != NULL);
+    g_assert(actual == NULL);
+    g_assert_cmpint(len, ==, 0);
+    error_free(err);
+}
+
+
+static void test_base64_embedded_nul(void)
+{
+    /* We put a NUL character in the middle of the base64
+     * text which is invalid data, given the expected length */
+    const char input[] =
+        "QmVjYXVzZSB3ZSBmb2N1c2VkIG9uIHRoZSBzbmFrZSwgd2UgbW\0"
+        "lzc2VkIHRoZSBzY29ycGlvbi4=";
+
+    test_base64_bad(input, G_N_ELEMENTS(input) - 1);
+}
+
+
+static void test_base64_not_nul_terminated(void)
+{
+    const char input[] =
+        "QmVjYXVzZSB3ZSBmb2N1c2VkIG9uIHRoZSBzbmFrZSwgd2UgbW\n"
+        "lzc2VkIHRoZSBzY29ycGlvbi4=";
+
+    /* Using '-2' to make us drop the trailing NUL, thus
+     * creating an invalid base64 sequence for decoding */
+    test_base64_bad(input, G_N_ELEMENTS(input) - 2);
+}
+
+
+static void test_base64_invalid_chars(void)
+{
+    /* We put a single quote character in the middle
+     * of the base64 text which is invalid data */
+    const char input[] =
+        "QmVjYXVzZSB3ZSBmb2N1c2VkIG9uIHRoZSBzbmFrZSwgd2UgbW'"
+        "lzc2VkIHRoZSBzY29ycGlvbi4=";
+
+    test_base64_bad(input, strlen(input));
+}
+
+
+int main(int argc, char **argv)
+{
+    g_test_init(&argc, &argv, NULL);
+    g_test_add_func("/util/base64/good", test_base64_good);
+    g_test_add_func("/util/base64/embedded-nul", test_base64_embedded_nul);
+    g_test_add_func("/util/base64/not-nul-terminated",
+                    test_base64_not_nul_terminated);
+    g_test_add_func("/util/base64/invalid-chars", test_base64_invalid_chars);
+    return g_test_run();
+}