[Fix] Fix rfc based base32 decoding

diff --git a/src/libutil/str_util.c b/src/libutil/str_util.c
index 5245cd516e22f6188b462544d635e74a0a855b20..c503396a2c89dc847afe0612ad2b3bbe946e7ca7 100644 (file)
--- a/src/libutil/str_util.c
+++ b/src/libutil/str_util.c
@@ -826,6 +826,7 @@ rspamd_decode_base32_buf (const gchar *in, gsize inlen, guchar *out, gsize outle
        guint processed_bits = 0;
        gsize i;
        const guchar *b32_dec;
+       bool inverse_bits = true;
 
        end = out + outlen;
        o = out;
@@ -836,38 +837,77 @@ rspamd_decode_base32_buf (const gchar *in, gsize inlen, guchar *out, gsize outle
                break;
        case RSPAMD_BASE32_BLEACH:
                b32_dec = b32_dec_bleach;
+               inverse_bits = false;
                break;
        case RSPAMD_BASE32_RFC:
                b32_dec = b32_dec_rfc;
+               inverse_bits = false;
                break;
        default:
                g_assert_not_reached ();
                abort ();
        }
 
-       for (i = 0; i < inlen; i ++) {
-               c = (guchar)in[i];
+       if (inverse_bits) {
+               for (i = 0; i < inlen; i++) {
+                       c = (guchar) in[i];
 
-               if (processed_bits >= 8) {
-                       processed_bits -= 8;
-                       *o++ = acc & 0xFF;
-                       acc >>= 8;
+                       if (processed_bits >= 8) {
+                               /* Emit from left to right */
+                               processed_bits -= 8;
+                               *o++ = acc & 0xFF;
+                               acc >>= 8;
+                       }
+
+                       decoded = b32_dec[c];
+                       if (decoded == 0xff || o >= end) {
+                               return -1;
+                       }
+
+                       acc = (decoded << processed_bits) | acc;
+                       processed_bits += 5;
                }
 
-               decoded = b32_dec[c];
-               if (decoded == 0xff || o >= end) {
+               if (processed_bits > 0 && o < end) {
+                       *o++ = (acc & 0xFF);
+               }
+               else if (o > end) {
                        return -1;
                }
-
-               acc = (decoded << processed_bits) | acc;
-               processed_bits += 5;
        }
+       else {
+               for (i = 0; i < inlen; i++) {
+                       c = (guchar) in[i];
 
-       if (processed_bits > 0 && o < end) {
-               *o++ = (acc & 0xFF);
-       }
-       else if (o > end) {
-               return -1;
+                       decoded = b32_dec[c];
+                       if (decoded == 0xff) {
+                               return -1;
+                       }
+
+                       acc = (acc << 5) | decoded;
+                       processed_bits += 5;
+
+                       if (processed_bits >= 8) {
+                               /* Emit from right to left */
+                               processed_bits -= 8;
+
+                               /* Output buffer overflow */
+                               if (o >= end) {
+                                       return -1;
+                               }
+
+                               *o++ = (acc >> processed_bits) & 0xFF;
+                               /* Preserve lowers at the higher parts of the input */
+                               acc = (acc & ((1u << processed_bits) - 1));
+                       }
+               }
+
+               if (processed_bits > 0 && o < end) {
+                       *o++ = (acc & 0xFF);
+               }
+               else if (o > end) {
+                       return -1;
+               }
        }
 
        return (o - out);