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Fixed url_sig error when storing base64ed params in penultimate segment. #4042

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Merged
SolidWallOfCode merged 1 commit into from
Aug 6, 2018
Merged

Fixed url_sig error when storing base64ed params in penultimate segment. #4042

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111 changes: 83 additions & 28 deletions plugins/experimental/url_sig/url_sig.c
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Original file line number Diff line number Diff line change
Expand Up @@ -330,23 +330,50 @@ getAppQueryString(const char *query_string, int query_length)
}
}

/** fixedBufferWrite safely writes no more than *dest_len bytes to *dest_end
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@SolidWallOfCode SolidWallOfCode Aug 2, 2018

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Did you consider using ts::FixedBufferWriter for this?

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@alficles alficles Aug 3, 2018

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Nope. Is there a straight C version though? I am mostly just trying to get the code back to what it used to do before strncat got turned into memcpy.

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@SolidWallOfCode SolidWallOfCode Aug 3, 2018

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Yeah, no C version. Dang. I keep forgetting people still write code in C. Oh well, nevermind.

* from src. If copying src_len bytes to *dest_len would overflow, it returns
* zero. *dest_end is advanced and *dest_len is decremented to account for the
* written data. No null-terminators are written automatically (though they
* could be copied with data).
*/
static int
fixedBufferWrite(char **dest_end, int *dest_len, const char *src, int src_len)
{
if (src_len > *dest_len) {
return 0;
}
memcpy(*dest_end, src, src_len);
*dest_end += src_len;
*dest_len -= src_len;
return 1;
}

static char *
urlParse(char *url, char *anchor, char *new_path_seg, int new_path_seg_len, char *signed_seg, unsigned int signed_seg_len)
{
char *segment[MAX_SEGMENTS];
unsigned char decoded_string[2048] = {'\0'};
char new_url[8192] = {'\0'};
char new_url[8192]; /* new_url is not null_terminated */
char *p = NULL, *sig_anchor = NULL, *saveptr = NULL;
int i = 0, numtoks = 0, cp_len = 0, l, decoded_len = 0, sig_anchor_seg = 0;
int i = 0, numtoks = 0, decoded_len = 0, sig_anchor_seg = 0;

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@ezelkow1 ezelkow1 Jul 31, 2018

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could use nullchecks on all the things

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@alficles alficles Aug 3, 2018

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No null checks in the old things, and my goal wasn't wholesale rewrite, but just a return to existing behavior. These are pretty safe, though, cause if we get a null ptr here, we're already in pretty bad shape much earlier.

char *new_url_end = new_url;
int new_url_len_left = sizeof(new_url);

char *new_path_seg_end = new_path_seg;
int new_path_seg_len_left = new_path_seg_len;

char *skip = strchr(url, ':');
if (!skip || skip[1] != '/' || skip[2] != '/') {
return NULL;
}
skip += 3;
// preserve the scheme in the new_url.
strncat(new_url, url, skip - url);
TSDebug(PLUGIN_NAME, "%s:%d - new_url: %s\n", __FILE__, __LINE__, new_url);
if (!fixedBufferWrite(&new_url_end, &new_url_len_left, url, skip - url)) {
TSError("insufficient space to copy schema into new_path_seg buffer.");
return NULL;
}
TSDebug(PLUGIN_NAME, "%s:%d - new_url: %*s\n", __FILE__, __LINE__, (int)(new_url_end - new_url), new_url);

// parse the url.
if ((p = strtok_r(skip, "/", &saveptr)) != NULL) {
Expand Down Expand Up @@ -387,19 +414,18 @@ urlParse(char *url, char *anchor, char *new_path_seg, int new_path_seg_len, char
// last path segment so skip them.
continue;
}
l = strlen(segment[i]);
if (l + 1 > new_path_seg_len) {
TSError("insuficient space to copy into new_path_seg buffer.");
if (!fixedBufferWrite(&new_path_seg_end, &new_path_seg_len_left, segment[i], strlen(segment[i]))) {
TSError("insufficient space to copy into new_path_seg buffer.");
return NULL;
} else {
memcpy(new_path_seg, segment[i], l);
new_path_seg[l] = '\0';
if (i != numtoks - 1) {
strncat(new_path_seg, "/", 1);
}
if (i != numtoks - 1) {
if (!fixedBufferWrite(&new_path_seg_end, &new_path_seg_len_left, "/", 1)) {
TSError("insufficient space to copy into new_path_seg buffer.");
return NULL;
}
cp_len += l + 1;
}
}
*new_path_seg_end = '\0';
TSDebug(PLUGIN_NAME, "new_path_seg: %s", new_path_seg);

// save the encoded signing parameter data
Expand Down Expand Up @@ -434,24 +460,53 @@ urlParse(char *url, char *anchor, char *new_path_seg, int new_path_seg_len, char
}
TSDebug(PLUGIN_NAME, "decoded_string: %s", decoded_string);

for (i = 0; i < numtoks; i++) {
// cp the base64 decoded string.
if (i == sig_anchor_seg && sig_anchor != NULL) {
memcpy(new_url, segment[i], strlen(segment[i]));
memcpy(new_url, (char *)decoded_string, strlen((char *)decoded_string));
strncat(new_url, "/", 1);
continue;
} else if (i == numtoks - 2 && sig_anchor == NULL) {
memcpy(new_url, (char *)decoded_string, strlen((char *)decoded_string));
strncat(new_url, "/", 1);
continue;
{
int oob = 0; /* Out Of Buffer */

for (i = 0; i < numtoks; i++) {
// cp the base64 decoded string.
if (i == sig_anchor_seg && sig_anchor != NULL) {
if (!fixedBufferWrite(&new_url_end, &new_url_len_left, segment[i], strlen(segment[i]))) {
oob = 1;
break;
}
if (!fixedBufferWrite(&new_url_end, &new_url_len_left, (char *)decoded_string, strlen((char *)decoded_string))) {
oob = 1;
break;
}
if (!fixedBufferWrite(&new_url_end, &new_url_len_left, "/", 1)) {
oob = 1;
break;
}

continue;
} else if (i == numtoks - 2 && sig_anchor == NULL) {
if (!fixedBufferWrite(&new_url_end, &new_url_len_left, (char *)decoded_string, strlen((char *)decoded_string))) {
oob = 1;
break;
}
if (!fixedBufferWrite(&new_url_end, &new_url_len_left, "/", 1)) {
oob = 1;
break;
}
continue;
}
if (!fixedBufferWrite(&new_url_end, &new_url_len_left, segment[i], strlen(segment[i]))) {
oob = 1;
break;
}
if (i < numtoks - 1) {
if (!fixedBufferWrite(&new_url_end, &new_url_len_left, "/", 1)) {
oob = 1;
break;
}
}
}
memcpy(new_url, segment[i], strlen(segment[i]));
if (i < numtoks - 1) {
strncat(new_url, "/", 1);
if (oob) {
TSError("insufficient space to copy into new_url.");
}
}
return TSstrndup(new_url, strlen(new_url));
return TSstrndup(new_url, new_url_end - new_url);
}

TSRemapStatus
Expand Down