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-rw-r--r--generic/tclBinary.c96
1 files changed, 69 insertions, 27 deletions
diff --git a/generic/tclBinary.c b/generic/tclBinary.c
index 3d8b24c..5c33308 100644
--- a/generic/tclBinary.c
+++ b/generic/tclBinary.c
@@ -2658,12 +2658,12 @@ BinaryDecode64(
Tcl_Obj *const objv[])
{
Tcl_Obj *resultObj = NULL;
- unsigned char *data, *datastart, *dataend, c;
+ unsigned char *data, *datastart, *dataend, c = '\0';
unsigned char *begin = NULL;
unsigned char *cursor = NULL;
int strict = 0;
int i, index, size, cut = 0, count = 0;
- enum {OPT_STRICT };
+ enum { OPT_STRICT };
static const char *const optStrings[] = { "-strict", NULL };
if (objc < 2 || objc > 3) {
@@ -2691,43 +2691,85 @@ BinaryDecode64(
while (data < dataend) {
unsigned long value = 0;
- for (i=0 ; i<4 ; i++) {
+ /*
+ * Decode the current block. Each base64 block consists of four input
+ * characters A-Z, a-z, 0-9, +, or /. Each character supplies six bits
+ * of output data, so each block's output is 24 bits (three bytes) in
+ * length. The final block can be shorter by one or two bytes, denoted
+ * by the input ending with one or two ='s, respectively.
+ */
+
+ for (i = 0; i < 4; i++) {
+ /*
+ * Get the next input character. At end of input, pad with at most
+ * two ='s. If more than two ='s would be needed, instead discard
+ * the block read thus far.
+ */
+
if (data < dataend) {
c = *data++;
+ } else if (i > 1) {
+ c = '=';
+ } else {
+ cut += 3;
+ break;
+ }
- if (c >= 'A' && c <= 'Z') {
- value = (value << 6) | ((c - 'A') & 0x3f);
- } else if (c >= 'a' && c <= 'z') {
- value = (value << 6) | ((c - 'a' + 26) & 0x3f);
- } else if (c >= '0' && c <= '9') {
- value = (value << 6) | ((c - '0' + 52) & 0x3f);
- } else if (c == '+') {
- value = (value << 6) | 0x3e;
- } else if (c == '/') {
- value = (value << 6) | 0x3f;
- } else if (c == '=') {
- value <<= 6;
- if (cut < 2) {
- cut++;
- }
+ /*
+ * Load the character into the block value. Handle ='s specially
+ * because they're only valid as the last character or two of the
+ * final block of input. Unless strict mode is enabled, skip any
+ * input whitespace characters.
+ */
+
+ if (cut) {
+ if (c == '=' && i > 1) {
+ value <<= 6;
+ cut++;
+ } else if (!strict && isspace(c)) {
+ i--;
} else {
- if (strict || !isspace(c)) {
- goto bad64;
- }
- i--;
- continue;
+ goto bad64;
}
- } else {
+ } else if (c >= 'A' && c <= 'Z') {
+ value = (value << 6) | ((c - 'A') & 0x3f);
+ } else if (c >= 'a' && c <= 'z') {
+ value = (value << 6) | ((c - 'a' + 26) & 0x3f);
+ } else if (c >= '0' && c <= '9') {
+ value = (value << 6) | ((c - '0' + 52) & 0x3f);
+ } else if (c == '+') {
+ value = (value << 6) | 0x3e;
+ } else if (c == '/') {
+ value = (value << 6) | 0x3f;
+ } else if (c == '=') {
value <<= 6;
cut++;
+ } else if (strict || !isspace(c)) {
+ goto bad64;
+ } else {
+ i--;
}
}
*cursor++ = UCHAR((value >> 16) & 0xff);
*cursor++ = UCHAR((value >> 8) & 0xff);
*cursor++ = UCHAR(value & 0xff);
- }
- if (cut > size) {
- cut = size;
+
+ /*
+ * Since = is only valid within the final block, if it was encountered
+ * but there are still more input characters, confirm that strict mode
+ * is off and all subsequent characters are whitespace.
+ */
+
+ if (cut && data < dataend) {
+ if (strict) {
+ goto bad64;
+ }
+ for (; data < dataend; data++) {
+ if (!isspace(*data)) {
+ goto bad64;
+ }
+ }
+ }
}
Tcl_SetByteArrayLength(resultObj, cursor - begin - cut);
Tcl_SetObjResult(interp, resultObj);