commit f311d0676caad1c61a4dbf8fffbeb79003866903 Author: teor teor@torproject.org Date: Tue Sep 3 15:50:37 2019 +1000

backtrace: Check the return values of snprintf() and strncpy()

We can't use strlcat() or strlcpy() in torerr, because they are defined in string/compat_string.h on some platforms, and string uses torerr.

Part of 31571. --- src/lib/err/backtrace.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/src/lib/err/backtrace.c b/src/lib/err/backtrace.c index a4d8269c6..8606f4217 100644 --- a/src/lib/err/backtrace.c +++ b/src/lib/err/backtrace.c @@ -276,11 +276,23 @@ configure_backtrace_handler(const char *tor_version) char version[128] = "Tor\0";

if (tor_version) { - snprintf(version, sizeof(version), "Tor %s", tor_version); + int snp_rv = 0; + /* We can't use strlcat() here, because it is defined in + * string/compat_string.h on some platforms, and string uses torerr. */ + snp_rv = snprintf(version, sizeof(version), "Tor %s", tor_version); + /* It's safe to call raw_assert() here, because raw_assert() does not + * call configure_backtrace_handler(). */ + raw_assert(snp_rv < (int)sizeof(version)); + raw_assert(snp_rv >= 0); }

- strncpy(bt_version, version, sizeof(bt_version) - 1); + char *str_rv = NULL; + /* We can't use strlcpy() here, see the note about strlcat() above. */ + str_rv = strncpy(bt_version, version, sizeof(bt_version) - 1); + /* We must terminate bt_version, then raw_assert(), because raw_assert() + * uses bt_version. */ bt_version[sizeof(bt_version) - 1] = 0; + raw_assert(str_rv == bt_version);

return install_bt_handler(); }