fix potential buffer overrun and negative array index bugs

diff --git a/lib/base64.c b/lib/base64.c
index d348e034f57fde0bcc26e6ebd3c37f5067568250..60f797b27eecf7d5ef211f0a8794e4f2470845d9 100644 (file)
--- a/lib/base64.c
+++ b/lib/base64.c
@@ -1,5 +1,5 @@
 /*
- * $Id: base64.c,v 1.15 1998/09/23 17:14:21 wessels Exp $
+ * $Id: base64.c,v 1.16 1998/10/14 02:40:25 wessels Exp $
  */
 
 #include "config.h"
@@ -14,7 +14,9 @@
 static void base64_init(void);
 
 static int base64_initialized = 0;
-int base64_value[256];
+#define BASE64_VALUE_SZ 256
+#define BASE64_RESULT_SZ 8192
+int base64_value[BASE64_VALUE_SZ];
 const char base64_code[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
 
 
@@ -23,7 +25,7 @@ base64_init(void)
 {
     int i;
 
-    for (i = 0; i < 256; i++)
+    for (i = 0; i < BASE64_VALUE_SZ; i++)
        base64_value[i] = -1;
 
     for (i = 0; i < 64; i++)
@@ -36,42 +38,39 @@ base64_init(void)
 char *
 base64_decode(const char *p)
 {
-    static char result[8192];
+    static char result[BASE64_RESULT_SZ];
+    int j;
+    unsigned int k;
     int c;
     long val;
-    int i;
-    char *d;
-
     if (!p)
        return NULL;
-
     if (!base64_initialized)
        base64_init();
-
     val = c = 0;
-    d = result;
-    while (*p) {
-       i = base64_value[(int) *p++];
-       if (i >= 0) {
-           val = val * 64 + i;
-           c++;
-       }
-       if (c == 4) {           /* One quantum of four encoding characters/24 bit */
-           *d++ = val >> 16;   /* High 8 bits */
-           *d++ = (val >> 8) & 0xff;   /* Mid 8 bits */
-           *d++ = val & 0xff;  /* Low 8 bits */
-           val = c = 0;
-       }
+    for (j = 0; *p && j + 3 < BASE64_RESULT_SZ; p++) {
+       k = (int) *p % BASE64_VALUE_SZ;
+       if (base64_value[k] < 0)
+           continue;
+       val <<= 6;
+       val += base64_value[k];
+       if (++c < 4)
+           continue;
+       /* One quantum of four encoding characters/24 bit */
+       result[j++] = val >> 16;        /* High 8 bits */
+       result[j++] = (val >> 8) & 0xff;        /* Mid 8 bits */
+       result[j++] = val & 0xff;       /* Low 8 bits */
+       val = c = 0;
     }
-    *d = 0;
-    return *result ? result : NULL;
+    result[j] = 0;
+    return result;
 }
 
 /* adopted from http://ftp.sunet.se/pub2/gnu/vm/base64-encode.c with adjustments */
 const char *
 base64_encode(const char *decoded_str)
 {
-    static char result[8192];
+    static char result[BASE64_RESULT_SZ];
     int bits = 0;
     int char_count = 0;
     int out_cnt = 0;