Patch by Jason Trowbridge. (Followup to his PR#110.) (Slightly
reformatted.)
- Illegal padding is now ignored. (Recommendation by GvR.)
- Padding no longer removes characters from data string (resulting in
lost data/strings with negative lengths).
- Illegal characters outside the ASCII range are now ignored, instead
of possibly being remapped to a valid character.
diff --git a/Modules/binascii.c b/Modules/binascii.c
index 601169c..fef4428 100644
--- a/Modules/binascii.c
+++ b/Modules/binascii.c
@@ -328,6 +328,35 @@
return rv;
}
+
+static int
+binascii_find_valid(s, slen, num)
+ char *s;
+ int slen;
+ int num;
+{
+ /* Finds & returns the (num+1)th
+ ** valid character for base64, or -1 if none.
+ */
+
+ int ret = -1;
+ unsigned char c, b64val;
+
+ while ((slen > 0) && (ret == -1)) {
+ c = *s;
+ b64val = table_a2b_base64[c & 0x7f];
+ if ( ((c <= 0x7f) && (b64val != (unsigned char)-1)) ) {
+ if (num == 0)
+ ret = *s;
+ num--;
+ }
+
+ s++;
+ slen--;
+ }
+ return ret;
+}
+
static char doc_a2b_base64[] = "(ascii) -> bin. Decode a line of base64 data";
static PyObject *
@@ -339,9 +368,9 @@
int leftbits = 0;
unsigned char this_ch;
unsigned int leftchar = 0;
- int npad = 0;
PyObject *rv;
int ascii_len, bin_len;
+ int quad_pos = 0;
if ( !PyArg_ParseTuple(args, "t#", &ascii_data, &ascii_len) )
return NULL;
@@ -353,39 +382,61 @@
return NULL;
bin_data = (unsigned char *)PyString_AsString(rv);
bin_len = 0;
- for( ; ascii_len > 0 ; ascii_len--, ascii_data++ ) {
- /* Skip some punctuation */
- this_ch = (*ascii_data & 0x7f);
- if ( this_ch == '\r' || this_ch == '\n' || this_ch == ' ' )
+
+ for( ; ascii_len > 0; ascii_len--, ascii_data++) {
+ this_ch = *ascii_data;
+
+ if (this_ch > 0x7f ||
+ this_ch == '\r' || this_ch == '\n' || this_ch == ' ')
continue;
-
- if ( this_ch == BASE64_PAD )
- npad++;
- this_ch = table_a2b_base64[(*ascii_data) & 0x7f];
- if ( this_ch == (unsigned char) -1 ) continue;
+
+ /* Check for pad sequences and ignore
+ ** the invalid ones.
+ */
+ if (this_ch == BASE64_PAD) {
+ if ( (quad_pos < 2) ||
+ ((quad_pos == 2) &&
+ (binascii_find_valid(ascii_data, ascii_len, 1)
+ != BASE64_PAD)) )
+ {
+ continue;
+ }
+ else {
+ /* A pad sequence means no more input.
+ ** We've already interpreted the data
+ ** from the quad at this point.
+ */
+ leftbits = 0;
+ break;
+ }
+ }
+
+ this_ch = table_a2b_base64[*ascii_data];
+ if ( this_ch == (unsigned char) -1 )
+ continue;
+
/*
** Shift it in on the low end, and see if there's
** a byte ready for output.
*/
+ quad_pos = (quad_pos + 1) & 0x03;
leftchar = (leftchar << 6) | (this_ch);
leftbits += 6;
+
if ( leftbits >= 8 ) {
leftbits -= 8;
*bin_data++ = (leftchar >> leftbits) & 0xff;
- leftchar &= ((1 << leftbits) - 1);
bin_len++;
+ leftchar &= ((1 << leftbits) - 1);
}
- }
- /* Check that no bits are left */
- if ( leftbits ) {
+ }
+
+ if (leftbits != 0) {
PyErr_SetString(Error, "Incorrect padding");
Py_DECREF(rv);
return NULL;
}
- /* and remove any padding */
- bin_len -= npad;
- if (bin_len < 0)
- bin_len = 0;
+
/* and set string size correctly */
_PyString_Resize(&rv, bin_len);
return rv;