Skip to content

Fix integer overflow #201

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
pennam wants to merge 3 commits into
base: master
Choose a base branch
from
+14 −6
Open

Fix integer overflow #201

Changes from all commits
Commits
Show all changes
3 commits
Select commit Hold shift + click to select a range
2624ec2
Fix signed overflow when parsing chunk length
pennam Jul 13, 2026
0e715a7
Prevent iChunkLength underflow in read()
pennam Jul 13, 2026
c762f8d
Harden Content-Length parsing against overflow
pennam Jul 13, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
20 changes: 14 additions & 6 deletions src/HttpClient.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@

#include "HttpClient.h"
#include "b64.h"
#include <limits.h>

// Initialize constants
const char* HttpClient::kUserAgent = "Arduino/2.2.0";
Expand Down Expand Up @@ -625,8 +626,12 @@ int HttpClient::available()
else if (isHexadecimalDigit(c))
{
char digit[2] = {c, '\0'};
int digitValue = (int)strtol(digit, NULL, 16);

iChunkLength = (iChunkLength * 16) + strtol(digit, NULL, 16);
// Only apply if the value fits in int without overflow.
if (iChunkLength <= ((INT_MAX - digitValue) / 16)) {

@andreagilardoni andreagilardoni Jul 13, 2026 •
edited
Loading

Copy link
Copy Markdown

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

This is equivalent, but I think it may be easier to read

Suggested change
if (iChunkLength <= ((INT_MAX - digitValue) / 16)) {
if ((iChunkLength * 16) + digitValue <= INT_MAX) {

iChunkLength = (iChunkLength * 16) + digitValue;
}
}
}
}
Expand Down Expand Up @@ -673,7 +678,10 @@ int HttpClient::read()

if (iState == eReadingBodyChunk)
{
iChunkLength--;
if (iChunkLength > 0)
{
iChunkLength--;
}

if (iChunkLength == 0)
{
Expand Down Expand Up @@ -819,10 +827,10 @@ int HttpClient::readHeader()
case eReadingContentLength:
if (isdigit(c))
{
long _iContentLength = iContentLength*10 + (c - '0');
// Only apply if the value didn't wrap around
if (_iContentLength > iContentLength) {
iContentLength = _iContentLength;
int digitValue = c - '0';
// Only apply if the value fits in long without overflow.
if (iContentLength <= ((LONG_MAX - digitValue) / 10)) {

@andreagilardoni andreagilardoni Jul 13, 2026 •
edited
Loading

Copy link
Copy Markdown

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

This is equivalent, but I think it may be easier to read

Suggested change
if (iContentLength <= ((LONG_MAX - digitValue) / 10)) {
if ((iContentLength * 10) + digitValue <= LONG_MAX) {

iContentLength = iContentLength * 10 + digitValue;
}
}
else
Expand Down