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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.
This commit is contained in:
Guido van Rossum 1999-10-19 19:05:14 +00:00
parent 7b8f1abfca
commit 2db4f47fdd
1 changed files with 69 additions and 18 deletions
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87
Modules/binascii.c
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@ -328,6 +328,35 @@ binascii_b2a_uu(self, args)
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 @@ binascii_a2b_base64(self, args)
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 @@ binascii_a2b_base64(self, args)
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;