Make base64 decoding table-driven.

diff --git a/plugins/sudoers/base64.c b/plugins/sudoers/base64.c
index d85bfbf59f9f4138124195f8168244aca51ee155..c8f9273c14c4a286a0eef300575d45938d500b50 100644 (file)
--- a/plugins/sudoers/base64.c
+++ b/plugins/sudoers/base64.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013-2015 Todd C. Miller <Todd.Miller@courtesan.com>
+ * Copyright (c) 2013-2016 Todd C. Miller <Todd.Miller@courtesan.com>
  *
  * Permission to use, copy, modify, and distribute this software for any
  * purpose with or without fee is hereby granted, provided that the above
@@ -30,44 +30,59 @@
 
 #include "sudoers.h"
 
+/*
+ * Derived from code with the following declaration:
+ *     PUBLIC DOMAIN - Jon Mayo - November 13, 2003 
+ */
+
+static const unsigned char base64dec_tab[256]= {
+    255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
+    255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
+    255,255,255,255,255,255,255,255,255,255,255, 62,255,255,255, 63,
+     52, 53, 54, 55, 56, 57, 58, 59, 60, 61,255,255,255,  0,255,255,
+    255,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14,
+     15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,255,255,255,255,255,
+    255, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
+     41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51,255,255,255,255,255,
+    255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
+    255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
+    255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
+    255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
+    255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
+    255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
+    255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
+    255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
+};
+
 /*
  * Decode a NUL-terminated string in base64 format and store the
  * result in dst.
  */
 size_t
-base64_decode(const char *str, unsigned char *dst, size_t dsize)
+base64_decode(const char *in, unsigned char *out, size_t out_size)
 {
-    static const char b64[] =
-       "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
-    const unsigned char *dst0 = dst;
-    const unsigned char *dend = dst + dsize;
-    unsigned char ch[4];
-    char *pos;
-    int i;
+    unsigned char *out_end = out + out_size;
+    const unsigned char *out0 = out;
+    unsigned int rem, v;
     debug_decl(base64_decode, SUDOERS_DEBUG_MATCH)
 
-    /*
-     * Convert from base64 to binary.  Each base64 char holds 6 bits of data
-     * so 4 base64 chars equals 3 chars of data.
-     * Padding (with the '=' char) may or may not be present.
-     */
-    while (*str != '\0') {
-       for (i = 0; i < 4; i++) {
-           if (*str == '=' || *str == '\0')
-               break;
-           if ((pos = strchr(b64, *str++)) == NULL)
+    for (v = 0, rem = 0; *in != '\0' && *in != '='; in++) {
+       unsigned char ch = base64dec_tab[(unsigned char)*in];
+       if (ch == 255)
+           debug_return_size_t((size_t)-1);
+       v = (v << 6) | ch;
+       rem += 6;
+       if (rem >= 8) {
+           rem -= 8;
+           if (out >= out_end)
                debug_return_size_t((size_t)-1);
-           ch[i] = (unsigned char)(pos - b64);
+           *out++ = (v >> rem) & 0xff;
        }
-       if (i == 0 || i == 1 || dst == dend)
-           break;
-       *dst++ = (ch[0] << 2) | ((ch[1] & 0x30) >> 4);
-       if (i == 2 || dst == dend)
-           break;
-       *dst++ = ((ch[1] & 0x0f) << 4) | ((ch[2] & 0x3c) >> 2);
-       if (i == 3 || dst == dend)
-           break;
-       *dst++ = ((ch[2] & 0x03) << 6) | ch[3];
     }
-    debug_return_size_t((size_t)(dst - dst0));
+    if (rem >= 8) {
+           if (out >= out_end)
+               debug_return_size_t((size_t)-1);
+           *out++ = (v >> rem) & 0xff;
+    }
+    debug_return_size_t((size_t)(out - out0));
 }