From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Peter Jones <pjones@redhat.com>
Date: Tue, 15 May 2018 11:20:15 -0400
Subject: [PATCH] generate_hash() / generate_pw_hash(): don't use strlen() for
 strncpy bounds

New gcc rightly comlplains when we do the following:

strncpy (dest, src, strlen(src));

For two reasons:
a) it doesn't copy the NUL byte
b) it's otherwise the same thing strcpy() would have done

This patch replaces that with stpncpy (just because it's slightly easier
to use) and the real bounds for the destination.

Signed-off-by: Peter Jones <pjones@redhat.com>
---
 src/mokutil.c | 33 ++++++++++++++++++++++-----------
 1 file changed, 22 insertions(+), 11 deletions(-)

diff --git a/src/mokutil.c b/src/mokutil.c
index 0be9e84..b508010 100644
--- a/src/mokutil.c
+++ b/src/mokutil.c
@@ -764,9 +764,10 @@ generate_hash (pw_crypt_t *pw_crypt, char *password, unsigned int pw_len)
 {
 	pw_crypt_t new_crypt;
 	char settings[SETTINGS_LEN];
+	char *next;
 	char *crypt_string;
 	const char *prefix;
-	int hash_len, prefix_len;
+	int hash_len, settings_len = sizeof (settings) - 2;
 
 	if (!password || !pw_crypt || password[pw_len] != '\0')
 		return -1;
@@ -774,15 +775,19 @@ generate_hash (pw_crypt_t *pw_crypt, char *password, unsigned int pw_len)
 	prefix = get_crypt_prefix (pw_crypt->method);
 	if (!prefix)
 		return -1;
-	prefix_len = strlen(prefix);
 
 	pw_crypt->salt_size = get_salt_size (pw_crypt->method);
 	generate_salt ((char *)pw_crypt->salt, pw_crypt->salt_size);
 
-	strncpy (settings, prefix, prefix_len);
-	strncpy (settings + prefix_len, (const char *)pw_crypt->salt,
-		 pw_crypt->salt_size);
-	settings[pw_crypt->salt_size + prefix_len] = '\0';
+	memset (settings, 0, sizeof (settings));
+	next = stpncpy (settings, prefix, settings_len);
+	if (pw_crypt->salt_size > settings_len - (next - settings)) {
+		errno = EOVERFLOW;
+		return -1;
+	}
+	next = stpncpy (next, (const char *)pw_crypt->salt,
+			pw_crypt->salt_size);
+	*next = '\0';
 
 	crypt_string = crypt (password, settings);
 	if (!crypt_string)
@@ -1929,10 +1934,11 @@ static int
 generate_pw_hash (const char *input_pw)
 {
 	char settings[SETTINGS_LEN];
+        char *next;
 	char *password = NULL;
 	char *crypt_string;
 	const char *prefix;
-	int prefix_len;
+	int settings_len = sizeof (settings) - 2;
 	unsigned int pw_len, salt_size;
 
 	if (input_pw) {
@@ -1958,12 +1964,17 @@ generate_pw_hash (const char *input_pw)
 	prefix = get_crypt_prefix (DEFAULT_CRYPT_METHOD);
 	if (!prefix)
 		return -1;
-	prefix_len = strlen(prefix);
 
-	strncpy (settings, prefix, prefix_len);
+	memset (settings, 0, sizeof (settings));
+	next = stpncpy (settings, prefix, settings_len);
 	salt_size = get_salt_size (DEFAULT_CRYPT_METHOD);
-	generate_salt ((settings + prefix_len), salt_size);
-	settings[DEFAULT_SALT_SIZE + prefix_len] = '\0';
+	if (salt_size > settings_len - (next - settings)) {
+		errno = EOVERFLOW;
+		return -1;
+	}
+	generate_salt (next, salt_size);
+	next += salt_size;
+	*next = '\0';
 
 	crypt_string = crypt (password, settings);
 	free (password);