Improve base64 encoding/decoding, add URL-safe variant.

[tinc] / src / utils.c

diff --git a/src/utils.c b/src/utils.c
index aefec8c..dca88d6 100644 (file)
--- a/src/utils.c
+++ b/src/utils.c
@@ -24,7 +24,26 @@
 #include "utils.h"
 
 static const char hexadecimals[] = "0123456789ABCDEF";
-static const char base64imals[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+static const char base64_original[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+static const char base64_urlsafe[] =  "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_";
+static const char base64_decode[256] = {
+       -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+       -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+       -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, 62, -1, 63,
+       52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1,
+       -1,  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, -1, -1, -1, -1, 63,
+       -1, 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, -1, -1, -1, -1, -1,
+       -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+       -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+       -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+       -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+       -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+       -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+       -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+       -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+};
 
 static int charhex2bin(char c) {
        if(isdigit(c))
@@ -33,19 +52,6 @@ static int charhex2bin(char c) {
                return toupper(c) - 'A' + 10;
 }
 
-static int charb64decode(char c) {
-       if(c >= 'a')
-               return c - 'a' + 26;
-       else if(c >= 'A')
-               return c - 'A';
-       else if(c >= '0')
-               return c - '0' + 52;
-       else if(c == '+')
-               return 62;
-       else
-               return 63;
-}
-
 int hex2bin(const char *src, char *dst, int length) {
        int i;
        for(i = 0; i < length && isxdigit(src[i * 2]) && isxdigit(src[i * 2 + 1]); i++)
@@ -68,8 +74,10 @@ int b64decode(const char *src, char *dst, int length) {
        unsigned char *udst = (unsigned char *)dst;
 
        for(i = 0; i < length / 3 * 4 && src[i]; i++) {
-               triplet |= charb64decode(src[i]) << (6 * (i & 3));
+               triplet |= base64_decode[src[i] & 0xff] << (6 * (i & 3));
                if((i & 3) == 3) {
+                       if(triplet & 0xff000000U)
+                               return 0;
                        udst[0] = triplet & 0xff; triplet >>= 8;
                        udst[1] = triplet & 0xff; triplet >>= 8;
                        udst[2] = triplet;
@@ -77,6 +85,8 @@ int b64decode(const char *src, char *dst, int length) {
                        udst += 3;
                }
        }
+       if(triplet & 0xff000000U)
+               return 0;
        if((i & 3) == 3) {
                udst[0] = triplet & 0xff; triplet >>= 8;
                udst[1] = triplet & 0xff;
@@ -89,7 +99,7 @@ int b64decode(const char *src, char *dst, int length) {
        }
 }
 
-int b64encode(const char *src, char *dst, int length) {
+static int b64encode_internal(const char *src, char *dst, int length, const char *alphabet) {
        uint32_t triplet;
        const unsigned char *usrc = (unsigned char *)src;
        int si = length / 3 * 3;
@@ -98,16 +108,16 @@ int b64encode(const char *src, char *dst, int length) {
        switch(length % 3) {
                case 2:
                        triplet = usrc[si] | usrc[si + 1] << 8;
-                       dst[di] = base64imals[triplet & 63]; triplet >>= 6;
-                       dst[di + 1] = base64imals[triplet & 63]; triplet >>= 6;
-                       dst[di + 2] = base64imals[triplet];
+                       dst[di] = alphabet[triplet & 63]; triplet >>= 6;
+                       dst[di + 1] = alphabet[triplet & 63]; triplet >>= 6;
+                       dst[di + 2] = alphabet[triplet];
                        dst[di + 3] = 0;
                        length = di + 2;
                        break;
                case 1:
                        triplet = usrc[si];
-                       dst[di] = base64imals[triplet & 63]; triplet >>= 6;
-                       dst[di + 1] = base64imals[triplet];
+                       dst[di] = alphabet[triplet & 63]; triplet >>= 6;
+                       dst[di + 1] = alphabet[triplet];
                        dst[di + 2] = 0;
                        length = di + 1;
                        break;
@@ -121,15 +131,23 @@ int b64encode(const char *src, char *dst, int length) {
                di -= 4;
                si -= 3;
                triplet = usrc[si] | usrc[si + 1] << 8 | usrc[si + 2] << 16;
-               dst[di] = base64imals[triplet & 63]; triplet >>= 6;
-               dst[di + 1] = base64imals[triplet & 63]; triplet >>= 6;
-               dst[di + 2] = base64imals[triplet & 63]; triplet >>= 6;
-               dst[di + 3] = base64imals[triplet];
+               dst[di] = alphabet[triplet & 63]; triplet >>= 6;
+               dst[di + 1] = alphabet[triplet & 63]; triplet >>= 6;
+               dst[di + 2] = alphabet[triplet & 63]; triplet >>= 6;
+               dst[di + 3] = alphabet[triplet];
        }
 
        return length;
 }
 
+int b64encode(const char *src, char *dst, int length) {
+       return b64encode_internal(src, dst, length, base64_original);
+}
+
+int b64encode_urlsafe(const char *src, char *dst, int length) {
+       return b64encode_internal(src, dst, length, base64_urlsafe);
+}
+
 #if defined(HAVE_MINGW) || defined(HAVE_CYGWIN)
 #ifdef HAVE_CYGWIN
 #include <w32api/windows.h>