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ensure that partial reads from recv don't trip up rendering #469

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58 changes: 34 additions & 24 deletions src/mod_tile.c
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Original file line number Diff line number Diff line change
Expand Up @@ -297,49 +297,59 @@
struct pollfd rx;
int s;

size_t already_read = 0;
size_t want = sizeof(struct protocol_v2);
bzero(&resp, sizeof(struct protocol));

while (1) {
rx.fd = fd;
rx.events = POLLIN;
s = poll(&rx, 1, timeout * 1000);

if (s > 0) {
bzero(&resp, sizeof(struct protocol));
ret = recv(fd, &resp, sizeof(struct protocol_v2), 0);
ret = recv(fd, &resp + already_read, want - already_read, 0);

Check notice

Code scanning / Flawfinder

Function accepts input from outside program (CWE-20). Note

input/recv:Function accepts input from outside program (CWE-20).

if (ret != sizeof(struct protocol_v2)) {
ap_log_rerror(APLOG_MARK, APLOG_WARNING, 0, r, "request_tile: Failed to read response from rendering socket. Got %d bytes but expected %d. Errno %d (%s)",
ret, (int)sizeof(struct protocol_v2), errno, strerror(errno));
// a return value of <= 0 means that there is some kind of error
if (ret <= 0) {
ap_log_rerror(APLOG_MARK, APLOG_WARNING, 0, r, "request_tile: Failed to read response from rendering socket: %s",
strerror(errno));
break;
}

if (resp.ver == 3) {
ret += recv(fd, ((void *)&resp) + sizeof(struct protocol_v2), sizeof(struct protocol) - sizeof(struct protocol_v2), 0);
}

if (cmd->x == resp.x && cmd->y == resp.y && cmd->z == resp.z && !strcmp(cmd->xmlname, resp.xmlname)) {
close(fd);

if (resp.cmd == cmdDone) {
return 1;
// other return values mean that some bytes were read, not necessary as many as we wanted
already_read += ret;
// first integer in message is protocol version
if (already_read >= sizeof(int))
want = (resp.ver == 3) ? sizeof(struct protocol) : sizeof(struct protocol_v2);

// do we have a complete packet?
if (already_read == want) {
if (cmd->x == resp.x && cmd->y == resp.y && cmd->z == resp.z && !strcmp(cmd->xmlname, resp.xmlname)) {
close(fd);

if (resp.cmd == cmdDone) {
return 1;
} else {
return 0;
}
} else {
return 0;
ap_log_rerror(APLOG_MARK, APLOG_WARNING, 0, r,
"Response does not match request: xml(%s,%s) z(%d,%d) x(%d,%d) y(%d,%d)", cmd->xmlname,
resp.xmlname, cmd->z, resp.z, cmd->x, resp.x, cmd->y, resp.y);
}
} else {
ap_log_rerror(APLOG_MARK, APLOG_WARNING, 0, r,
"Response does not match request: xml(%s,%s) z(%d,%d) x(%d,%d) y(%d,%d)", cmd->xmlname,
resp.xmlname, cmd->z, resp.z, cmd->x, resp.x, cmd->y, resp.y);
}
} else if (s == 0) {
ap_log_rerror(APLOG_MARK, APLOG_DEBUG, 0, r,
"request_tile: Request xml(%s) z(%d) x(%d) y(%d) could not be rendered in %i seconds",
cmd->xmlname, cmd->z, cmd->x, cmd->y,
timeout);
"request_tile: Request xml(%s) z(%d) x(%d) y(%d) could not be rendered in %i seconds",
cmd->xmlname, cmd->z, cmd->x, cmd->y,
timeout);
break;
} else {
ap_log_rerror(APLOG_MARK, APLOG_DEBUG, 0, r,
"request_tile: Request xml(%s) z(%d) x(%d) y(%d) timeout %i seconds failed with reason: %s",
cmd->xmlname, cmd->z, cmd->x, cmd->y,
timeout, strerror(errno));
"request_tile: Request xml(%s) z(%d) x(%d) y(%d) timeout %i seconds failed with reason: %s",
cmd->xmlname, cmd->z, cmd->x, cmd->y,
timeout, strerror(errno));
break;
}
}
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