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Fix potential buffer underflow when stripping trailing newlines - #1951
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Use std::string::back() and std::string::pop_back() (with a non-empty check) instead of indexing buf[strlen(buf) - 1] in app/src/locale.cc and testing/run_all_tests.cc, and close /etc/timezone in GetTimezone(). Resolves GitHub Code Scanning security alerts (Rule WS-CPP-00049): - https://github.com/firebase/firebase-cpp-sdk/security/code-scanning/2788 - https://github.com/firebase/firebase-cpp-sdk/security/code-scanning/2789 - https://github.com/firebase/firebase-cpp-sdk/security/code-scanning/2791
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This pull request fixes a potential 1-byte buffer underflow and a file descriptor leak when reading /etc/timezone in GetTimezone(), and refactors the test log printing loop to safely handle newlines. The review feedback suggests handling CRLF line endings when parsing /etc/timezone by stripping both \r and \n characters, and optimizing the test logging loop by manipulating the raw C-string buffer directly to avoid the overhead of creating a std::string on each iteration.
Replaces the C-style fgets + manual newline stripping in GetTimezone() and the Android test runner with std::getline, which has no fixed-size buffer, no index arithmetic, and closes the file via RAII. GetTimezone() now also trims a trailing '\r' from CRLF line endings.
a-maurice
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Oct 29, 2026
AustinBenoit
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October 29, 2026 17:49
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Description
Resolves GitHub Code Scanning security alerts (
WS-CPP-00049):app/src/locale.cc:235)app/src/locale.cc:236)testing/run_all_tests.cc:97)Both
firebase::internal::GetTimezone()(app/src/locale.cc) and the Android native test runner (testing/run_all_tests.cc) read lines usingfgetsinto a fixed buffer and stripped trailing newlines by indexingbuf[strlen(buf) - 1]. Iffgetsreads a line starting with a NUL byte (\0),strlenreturns0andlen - 1wraps around toSIZE_MAX(buf[-1]), resulting in a 1-byte buffer underflow. Intesting/run_all_tests.cc,log[strlen(log) - 1] = '\0'also truncated the 255th character of any line longer than the buffer that did not end with\n.This change:
buf[strlen(buf) - 1] = '\0') inapp/src/locale.ccandtesting/run_all_tests.ccwithstd::string(if (!str.empty() && str.back() == '\n') { str.pop_back(); }).char buf[kBufSize] = {0};andchar log[256] = {0};).tz_file(fclose(tz_file)) inGetTimezone()to fix aFILE*leak on Linux, and falls back togetenv("TZ")/tznameif/etc/timezoneis blank after stripping the newline.while (!feof(fp)) { if (fgets(...)) }intesting/run_all_tests.ccwithwhile (fgets(log, sizeof(log), fp) != nullptr)to avoid an infinite loop ifferror(fp)is set.### Upcominginrelease_build_files/readme.md.Testing
app/src/locale.ccon Linux desktop withg++ -std=c++17 -Wall -Wextra -Werror.python3 scripts/format_code.py -git_diff -noformat_file -verbose.bash scripts/gha/check_copyright.sh -g.Type of Change
Place an
xthe applicable box:https://github.com/firebase/firebase-cpp-sdk/security/code-scanning/2788
https://github.com/firebase/firebase-cpp-sdk/security/code-scanning/2789
https://github.com/firebase/firebase-cpp-sdk/security/code-scanning/2791
Notes
Release Notessection ofrelease_build_files/readme.md.