Fix host name retrieval during TLS certificate generation (#1935)

Use HOSTNAME if defined, otherwise invoke gethostname(3) if possible,
fallback to uname(2)

CMakeLists.txt

@@ -318,6 +318,8 @@ check_cxx_symbol_exists(lstat "sys/types.h;sys/stat.h;unistd.h" HAVE_LSTAT)
 check_cxx_symbol_exists(getpassphrase "stdlib.h" HAVE_GETPASSPHRASE)
 check_cxx_symbol_exists(tcsetattr "termios.h;unistd.h" HAVE_TCSETATTR)
 check_cxx_symbol_exists(clock_gettime "time.h" HAVE_CLOCK_GETTIME)
+check_cxx_symbol_exists(gethostname "unistd.h" ZNC_HAVE_GETHOSTNAME)
+check_cxx_symbol_exists(uname "sys/utsname.h" ZNC_HAVE_UNAME)
 
 # Note that old broken systems, such as OpenBSD, NetBSD, which don't support
 # AI_ADDRCONFIG, also have thread-unsafe getaddrinfo(). Gladly, they fixed

include/znc/Utils.h

@@ -44,6 +44,7 @@ class CUtils {
 
     static CString GetIP(unsigned long addr);
     static unsigned long GetLongIP(const CString& sIP);
+    static CString GetHostName();
 
     static void PrintError(const CString& sMessage);
     static void PrintMessage(const CString& sMessage, bool bStrong = false);
@@ -74,7 +75,7 @@ class CUtils {
     static timeval GetTime();
     static unsigned long long GetMillTime();
 #ifdef HAVE_LIBSSL
-    static void GenerateCert(FILE* pOut, const CString& sHost = "");
+    static void GenerateCert(FILE* pOut);
 #endif /* HAVE_LIBSSL */
 
     static CString CTime(time_t t, const CString& sTZ);

include/znc/zncconfig.h.cmake.in

@@ -43,6 +43,8 @@
 #cmakedefine HAVE_TCSETATTR 1
 #cmakedefine HAVE_GETPASSPHRASE 1
 #cmakedefine HAVE_CLOCK_GETTIME 1
+#cmakedefine ZNC_HAVE_GETHOSTNAME 1
+#cmakedefine ZNC_HAVE_UNAME 1
 
 #cmakedefine HAVE_ICU 1
 #define U_USING_ICU_NAMESPACE 1

src/Utils.cpp

@@ -38,6 +38,10 @@
 #include <unistd.h>
 #include <time.h>
 
+#ifdef ZNC_HAVE_GETHOSTNAME
+#include <limits.h>
+#endif
+
 #include <sys/types.h>
 #include <sys/socket.h>
 #include <netdb.h>
@@ -56,6 +60,10 @@
 #include <argon2.h>
 #endif
 
+#ifdef ZNC_HAVE_UNAME
+#include <sys/utsname.h>
+#endif
+
 // Required with GCC 4.3+ if openssl is disabled
 #include <cstring>
 #include <cstdlib>
@@ -82,7 +90,7 @@ constexpr const char* szDefaultDH2048 =
     "cvUyzAEcCQYHmiYjp2hoZbSa8b690TQaAwIBAg==\n"
     "-----END DH PARAMETERS-----\n";
 
-void CUtils::GenerateCert(FILE* pOut, const CString& sHost) {
+void CUtils::GenerateCert(FILE* pOut) {
     const int days = 365;
     const int years = 10;
 
@@ -112,25 +120,19 @@ void CUtils::GenerateCert(FILE* pOut, const CString& sHost) {
     X509_set_pubkey(pCert.get(), pKey.get());
 
     const char* pLogName = getenv("LOGNAME");
-    const char* pHostName = nullptr;
+    const CString sHostName = GetHostName();
 
     if (!pLogName) pLogName = "Unknown";
 
-    if (!sHost.empty()) pHostName = sHost.c_str();
-
-    if (!pHostName) pHostName = getenv("HOSTNAME");
-
-    if (!pHostName) pHostName = "host.unknown";
-
     CString sEmailAddr = pLogName;
     sEmailAddr += "@";
-    sEmailAddr += pHostName;
+    sEmailAddr += sHostName;
 
     X509_NAME* pName = X509_get_subject_name(pCert.get());
     X509_NAME_add_entry_by_txt(pName, "OU", MBSTRING_ASC,
                                (unsigned char*)pLogName, -1, -1, 0);
     X509_NAME_add_entry_by_txt(pName, "CN", MBSTRING_ASC,
-                               (unsigned char*)pHostName, -1, -1, 0);
+                               (unsigned char*)sHostName.c_str(), -1, -1, 0);
     X509_NAME_add_entry_by_txt(pName, "emailAddress", MBSTRING_ASC,
                                (unsigned char*)sEmailAddr.c_str(), -1, -1, 0);
 
@@ -180,6 +182,30 @@ unsigned long CUtils::GetLongIP(const CString& sIP) {
     return ret;
 }
 
+CString CUtils::GetHostName() {
+    const char *pEnv;
+
+    pEnv = getenv("HOSTNAME");
+    if (pEnv && pEnv[0])
+        return pEnv;
+
+#if defined(ZNC_HAVE_GETHOSTNAME) && defined(_POSIX_HOST_NAME_MAX)
+    char szBuffer[_POSIX_HOST_NAME_MAX + 1];
+    szBuffer[_POSIX_HOST_NAME_MAX] = 0;
+    if (gethostname(szBuffer, _POSIX_HOST_NAME_MAX) == 0)
+        return std::string(szBuffer);
+#endif
+
+#if defined(ZNC_HAVE_UNAME)
+    struct utsname UnameBuffer;
+
+    if (uname(&UnameBuffer) == 0 && UnameBuffer.nodename[0] != '\0')
+        return UnameBuffer.nodename;
+#endif
+
+    return "host.unknown";
+}
+
 #ifdef ZNC_HAVE_ARGON
 static CString SaltedArgonHash(const CString& sPass, const CString& sSalt) {
 #define ZNC_ARGON_PARAMS /* iterations */ 6, /* memory */ 6144, /* parallelism */ 1

src/znc.cpp

@@ -316,7 +316,7 @@ bool CZNC::WritePemFile() {
         return false;
     }
 
-    CUtils::GenerateCert(f, "");
+    CUtils::GenerateCert(f);
     fclose(f);
 
     CUtils::PrintStatus(true);