Make X509_NAME_get_text_by[NID|OBJ] safer.

This is an un-revert with nits of the previously landed change
to do this which broke libtls. libtls has now been changed to
not use this function.

This change ensures that if something is returned it is "text"
(UTF-8) and a C string not containing a NUL byte. Historically
callers to this function assume the result is text and a C string
however the OpenSSL version simply hands them the bytes from an
ASN1_STRING and expects them to know bad things can happen which
they almost universally do not check for. Partly inspired by
goings on in boringssl.

ok jsing@ tb@

1 files changed, 77 insertions, 2 deletions

diff --git a/regress/lib/libcrypto/x509/x509_asn1.c b/regress/lib/libcrypto/x509/x509_asn1.c
index d96a51880e2..4c038c9bbf4 100644
--- a/regress/lib/libcrypto/x509/x509_asn1.c
+++ b/regress/lib/libcrypto/x509/x509_asn1.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: x509_asn1.c,v 1.18 2023/05/03 08:10:23 beck Exp $ */
+/* $OpenBSD: x509_asn1.c,v 1.19 2023/05/29 11:54:50 beck Exp $ */
 /*
  * Copyright (c) 2023 Job Snijders <job@openbsd.org>
  *
@@ -512,13 +512,88 @@ test_x509_req_setters(void)
 	return failed;
 }
 
-int main(void)
+static const struct testcase {
+	char *data;
+	int len;
+	int len_to_pass;
+	int encode_type;
+	int expected_result;
+	char *expected_string;
+} testCases[] = {
+	/* should work */
+	{"fozzie", 6, 80, MBSTRING_ASC, 6, "fozzie"},
+	/* should work */
+	{"fozzie", 6, -1, MBSTRING_ASC, 6, ""},
+	/* should fail, truncation */
+	{"muppet", 6, 5, MBSTRING_ASC, -1, ""},
+	/* should fail, contains 0 byte */
+	{"g\0nzo", 5, 80, MBSTRING_ASC, -1, ""},
+	/* should fail, can't encode as utf-8 */
+	{"\x30\x00", 2, 80, V_ASN1_SEQUENCE, -1, ""},
+};
+
+#define NUM_TEST_CASES (sizeof(testCases) / sizeof(testCases[0]))
+
+static int
+test_x509_name_get(void)
+{
+	int failed = 0;
+	size_t i;
+
+	for (i = 0; i < NUM_TEST_CASES; i++) {
+		const struct testcase *test = testCases + i;
+		X509_NAME_ENTRY *entry = NULL;
+		X509_NAME *name = NULL;
+		char textbuf[80];
+		int result;
+
+		textbuf[0] = '\0';
+		if ((name = X509_NAME_new()) == NULL)
+			err(1, "X509_NAME_new");
+		if ((entry = X509_NAME_ENTRY_new()) == NULL)
+			err(1, "X509_NAME_ENTRY_new");
+		if (!X509_NAME_ENTRY_set_object(entry,
+		    OBJ_nid2obj(NID_commonName)))
+			err(1, "X509_NAME_ENTRY_set_object");
+		if (!X509_NAME_ENTRY_set_data(entry, test->encode_type,
+		    test->data, test->len))
+			err(1, "X509_NAME_ENTRY_set_data");
+		if (!X509_NAME_add_entry(name, entry, -1, 0))
+			err(1, "X509_NAME_add_entry");
+		if (test->len_to_pass == -1)
+			result = X509_NAME_get_text_by_NID(name, NID_commonName,
+			    NULL, 0);
+		else
+			result = X509_NAME_get_text_by_NID(name, NID_commonName,
+			    textbuf, test->len_to_pass);
+		if (result != test->expected_result) {
+			fprintf(stderr,
+			    "Test %zu X509_GET_text_by_NID returned %d,"
+			    "expected %d\n", i, result, test->expected_result);
+			failed++;
+		}
+		if (result != -1 &&
+		    strcmp(test->expected_string, textbuf) != 0) {
+			fprintf(stderr,
+			    "Test %zu, X509_GET_text_by_NID returned bytes do"
+			    "not match \n", i);
+			failed++;
+		}
+		X509_NAME_ENTRY_free(entry);
+		X509_NAME_free(name);
+	}
+	return failed;
+}
+
+int
+main(void)
 {
 	int failed = 0;
 
 	failed |= test_x509_setters();
 	/* failed |= */ test_x509_crl_setters();
 	/* failed |= */ test_x509_req_setters();
+	failed |= test_x509_name_get();
 
 	OPENSSL_cleanup();