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windows/certificates: Fix bug in environment variable expansion #5697

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merged 4 commits into from
Aug 13, 2019
Merged

windows/certificates: Fix bug in environment variable expansion #5697

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b2199dd
Explicitly handle when getUserHomeDir returns empty
offlinemark Aug 7, 2019
12237cd
Handle when ExpandEnvironmentStringsW does a partial write
offlinemark Aug 7, 2019
5d19236
Fix formatting
offlinemark Aug 8, 2019
24f6032
Fix ptr to temporary bug; remove retry loop
offlinemark Aug 9, 2019
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10 changes: 9 additions & 1 deletion osquery/tables/system/windows/certificates.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -531,7 +531,8 @@ void addCertRow(PCCERT_CONTEXT certContext,
}

Status expandEnvironmentVariables(const std::string& src, std::string& dest) {
auto srcW = stringToWstring(src).c_str();
auto srcWstring = stringToWstring(src);
auto srcW = srcWstring.c_str();
auto expandedSize = ExpandEnvironmentStringsW(srcW, nullptr, 0);
if (expandedSize == 0) {
return Status::failure("Unable to get expanded size");
Expand All @@ -541,6 +542,8 @@ Status expandEnvironmentVariables(const std::string& src, std::string& dest) {
auto ret = ExpandEnvironmentStringsW(srcW, buf.data(), expandedSize);
if (ret == 0) {
return Status::failure("Environment variable expansion failed");
} else if (ret != expandedSize) {
return Status::failure("Partial data written");
}

dest = wstringToString(buf.data());
Expand All @@ -557,6 +560,11 @@ void findUserPersonalCertsOnDisk(const std::string& username,

std::string homeDir;
auto homeDirUnexpanded = getUserHomeDir(sid);
if (homeDirUnexpanded.empty()) {
VLOG(1) << "Could not find home dir for account " << username;
return;
}

// System accounts have environment variables in their paths
auto ret = expandEnvironmentVariables(homeDirUnexpanded, homeDir);
if (!ret.ok() || homeDir.empty()) {
Expand Down