Skip to content

fix potential non-zero termination of a string buffer #2147

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

Merged
merged 2 commits into from
May 3, 2018
Merged

fix potential non-zero termination of a string buffer #2147

Changes from 1 commit
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
5907f68
fix potential non-zero termination of a string buffer
kroening May 3, 2018
9609a52
simplify use of get_temporary_directory
kroening May 3, 2018
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
19 changes: 10 additions & 9 deletions src/util/tempdir.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -15,7 +15,7 @@ Author: CM Wintersteiger
#endif

#include <cstdlib>
Copy link
Member

@peterschrammel peterschrammel May 3, 2018

Choose a reason for hiding this comment

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

Is the cstring include still required for non-win32?

Copy link
Collaborator

@tautschnig tautschnig May 3, 2018

Choose a reason for hiding this comment

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

Actually the _WIN32 part needs the very same fix, and then cstring isn't required at all anymore in here.

Copy link
Collaborator Author

@kroening kroening May 3, 2018

Choose a reason for hiding this comment

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

GetTempFileNameA actually appends to the string!

Copy link
Collaborator

@tautschnig tautschnig May 3, 2018

Choose a reason for hiding this comment

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

I don't understand. What does it append to which string? According to the documentation it will, given the current code, produce lpPathBuffer\TLO<some digits>.TMP.

Copy link
Collaborator Author

@kroening kroening May 3, 2018

Choose a reason for hiding this comment

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

Switched to vector on Windows as well.

#include <cstring>
#include <vector>

#if defined(__linux__) || \
defined(__FreeBSD_kernel__) || \
Expand All @@ -34,17 +34,18 @@ std::string get_temporary_directory(const std::string &name_template)
std::string result;

#ifdef _WIN32
DWORD dwBufSize = MAX_PATH;
char lpPathBuffer[MAX_PATH];
DWORD dwBufSize = MAX_PATH+1;
char lpPathBuffer[MAX_PATH+1];
Copy link
Collaborator

@tautschnig tautschnig May 3, 2018

Choose a reason for hiding this comment

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

The documentation of GetTempFileName says that it is a precondition that the path not be longer than MAX_PATH–14. Hence those changes seem unnecessary.

Copy link
Collaborator Author

@kroening kroening May 3, 2018

Choose a reason for hiding this comment

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

Yes; but that may be subtle. The documentation of GetTempPathA says that the maximal return value is MAX_PATH+1; this is the length of the buffer required.

DWORD dwRetVal = GetTempPathA(dwBufSize, lpPathBuffer);

if(dwRetVal > dwBufSize || (dwRetVal == 0))
throw "GetTempPath failed"; // NOLINT(readability/throw)

char t[MAX_PATH];

strncpy(t, name_template.c_str(), MAX_PATH);
// GetTempFileNameA produces <path>\<pre><uuuu>.TMP
// where <pre> = "TLO"
// Thus, we must make the buffer 1+3+4+1+3=12 characters longer.

char t[MAX_PATH];
UINT uRetVal=GetTempFileNameA(lpPathBuffer, "TLO", 0, t);
if(uRetVal == 0)
throw "GetTempFileName failed"; // NOLINT(readability/throw)
Expand All @@ -64,9 +65,9 @@ std::string get_temporary_directory(const std::string &name_template)
prefixed_name_template+='/';
prefixed_name_template+=name_template;

char t[1000];
strncpy(t, prefixed_name_template.c_str(), 1000);
const char *td = mkdtemp(t);
std::vector<char> t(prefixed_name_template.begin(), prefixed_name_template.end());
t.push_back('\0'); // add the zero
const char *td = mkdtemp(t.data());
if(!td)
throw "mkdtemp failed";
result=std::string(td);
Expand Down