Fixes for some defects found by Coverity

* Added more checks for return values and null pointers.
* Removed some dead code and unused variables.
* Fixed handling of calls to exec() family functions. If this functions
  fail we need to cleanup resources.

libhttp/httpconnection.c

@@ -183,18 +183,13 @@ static ssize_t httpWrite(struct HttpConnection *http, const char *buf,
 
 static int httpShutdown(struct HttpConnection *http, int how) {
   if (http->sslHndl) {
-    int rc        = 0;
     if (how != SHUT_RD) {
       dcheck(!ERR_peek_error());
       for (int i = 0; i < 10; i++) {
         sslBlockSigPipe();
-        rc        = SSL_shutdown(http->sslHndl);
+        int rc    = SSL_shutdown(http->sslHndl);
         int sPipe = sslUnblockSigPipe();
-        if (rc > 0) {
+        if (rc < 1) {
-          rc      = 0;
-          break;
-        } else {
-          rc      = -1;
           // Retry a few times in order to prefer a clean bidirectional
           // shutdown. But don't bother if the other side already closed
           // the connection.
@@ -1776,6 +1771,7 @@ void httpSendReply(struct HttpConnection *http, int code,
     response     = stringPrintf(response, "%s", body);
   }
   free(body);
+  check(response);
   httpTransfer(http, response, strlen(response));
   if (code != 200 || isHead) {
     httpCloseRead(http);

libhttp/server.c

@@ -338,7 +338,7 @@ void destroyServer(struct Server *server) {
   if (server) {
     if (server->serverFd >= 0) {
       info("Shutting down server");
-      close(server->serverFd);
+      NOINTR(close(server->serverFd));
     }
     for (int i = 0; i < server->numConnections; i++) {
       server->connections[i].destroyConnection(server->connections[i].arg);

libhttp/ssl.c

@@ -385,17 +385,21 @@ static void sslGenerateCertificate(const char *certificate,
     check(NOINTR(close(fd)) == 0);
     umask(077);
     check(setenv("PATH", "/usr/bin:/usr/sbin", 1) == 0);
-    execlp("openssl", "openssl", "req", "-x509", "-nodes", "-days", "7300",
+    char *subject;
+    check(subject = stringPrintf(NULL, "/CN=%s/", serverName));
+    if (execlp("openssl", "openssl", "req", "-x509", "-nodes", "-days", "7300",
                "-newkey", "rsa:2048", "-keyout", certificate, "-out", certificate,
-           "-subj", stringPrintf(NULL, "/CN=%s/", serverName),
+               "-subj", subject, (char *)NULL) < 0) {
-           (char *)NULL);
+      warn("Failed to generate self-signed certificate \"%s\"", certificate);
-    check(0);
+      free(subject);
+    }
   } else {
     int status;
     check(NOINTR(waitpid(pid, &status, 0)) == pid);
-    if (!WIFEXITED(status) || WEXITSTATUS(status) != 0)
+    if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
       warn("Failed to generate self-signed certificate \"%s\"", certificate);
     }
+  }
 }
 
 static const unsigned char *sslSecureReadASCIIFileToMem(int fd) {

libhttp/url.c

@@ -346,6 +346,7 @@ void initURL(struct URL *url, const struct HttpConnection *http,
   url->url                   = NULL;
   initHashMap(&url->args, urlDestroyHashMapEntry, NULL);
   if (!strcmp(http->method, "GET")) {
+    check(url->query);
     urlParseQueryString(&url->args, url->query, strlen(url->query));
   } else if (!strcmp(http->method, "POST")) {
     urlParsePostBody(url, http, buf, len);

shellinabox/launcher.c

@@ -273,7 +273,6 @@ static int read_string(int echo, const char *prompt, char **retstr) {
     term_tmp.c_lflag    &= ~ECHO;
   }
   int nc;
-  for (;;) {
   tcsetattr(0, TCSAFLUSH, &term_tmp);
   fprintf(stderr, "%s", prompt);
   char *line;
@@ -292,15 +291,12 @@ static int read_string(int echo, const char *prompt, char **retstr) {
     }
     line[nc]           = '\000';
     check(*retstr      = line);
-      break;
   } else {
     memset(line, 0, lineLength);
     free(line);
     if (echo) {
       fprintf(stderr, "\n");
     }
-      break;
-    }
   }
   tcsetattr(0, TCSADRAIN, &term_before);
   return nc;
@@ -711,6 +707,7 @@ void closeAllFds(int *exceptFds, int num) {
   // Close all file handles. If possible, scan through "/proc/self/fd" as
   // that is faster than calling close() on all possible file handles.
   int nullFd  = open("/dev/null", O_RDWR);
+  check(nullFd > 2);
   DIR *dir    = opendir("/proc/self/fd");
   if (dir == 0) {
     for (int i = sysconf(_SC_OPEN_MAX); --i > 0; ) {
@@ -805,7 +802,7 @@ static int forkPty(int *pty, int useLogin, struct Utmp **utmp,
     size_t length = 32;
     char* path = NULL;
     while (path == NULL) {
-      path = malloc (length);
+      check(path = malloc(length));
       *path = 0;
       if (ptsname_r (*pty, path, length)) {
         if (errno == ERANGE) {
@@ -913,7 +910,7 @@ static int forkPty(int *pty, int useLogin, struct Utmp **utmp,
     (*utmp)->utmpx.ut_pid   = pid;
 #endif
     (*utmp)->pty            = *pty;
-    fcntl(*pty, F_SETFL, O_NONBLOCK|O_RDWR);
+    check(!fcntl(*pty, F_SETFL, O_NONBLOCK | O_RDWR));
     NOINTR(close(slave));
     return pid;
   }
@@ -1449,7 +1446,6 @@ static void execService(int width ATTR_UNUSED, int height ATTR_UNUSED,
 
   extern char **environ;
   environ                     = environment;
-  char *cmd                   = strdup(argv[0]);
   char *slash                 = strrchr(argv[0], '/');
   if (slash) {
     memmove(argv[0], slash + 1, strlen(slash));
@@ -1461,7 +1457,12 @@ static void execService(int width ATTR_UNUSED, int height ATTR_UNUSED,
     argv[0][0]                = '-';
     argv[0][len + 1]          = '\000';
   }
-  execvp(cmd, argv);
+  char *cmd;
+  check(cmd                   = strdup(argv[0]));
+  if (execvp(cmd, argv) < 0) {
+    free(argv);
+    free(cmd);
+  }
 }
 
 void setWindowSize(int pty, int width, int height) {

shellinabox/privileges.c

@@ -103,7 +103,7 @@ static void removeGroupPrivileges(int showError) {
 
   if (runAsGroup >= 0) {
     uid_t ru, eu, su;
-    getresuid(&ru, &eu, &su);
+    check(!getresuid(&ru, &eu, &su));
 
     // Try to switch the user-provided group.
     if ((ru && runAsGroup != (int)rg) ||

shellinabox/shellinaboxd.c

@@ -503,6 +503,9 @@ static void serveStaticFile(HttpConnection *http, const char *contentType,
       if (!memcmp(ptr, "[if ", 4)) {
         char *bracket            = memchr(ptr + 4, ']', eol - ptr - 4);
         if (bracket != NULL && bracket > ptr + 4) {
+          if (tag != NULL) {
+            free(tag);
+          }
           check(tag              = malloc(bracket - ptr - 3));
           memcpy(tag, ptr + 4, bracket - ptr - 4);
           tag[bracket - ptr - 4] = '\000';
@@ -944,7 +947,7 @@ static void parseArgs(int argc, char * const argv[]) {
         fatal("Only one certificate file handle can be provided");
       }
       if (!optarg || *optarg < '0' || *optarg > '9') {
-        fatal("\"--cert-fd\" expects a valid file handle");
+        fatal("Option \"--cert-fd\" expects a valid file handle.");
       }
       int tmpFd            = strtoint(optarg, 3, INT_MAX);
       certificateFd        = dup(tmpFd);
@@ -956,7 +959,7 @@ static void parseArgs(int argc, char * const argv[]) {
       // CSS
       struct stat st;
       if (!optarg || !*optarg || stat(optarg, &st) || !S_ISREG(st.st_mode)) {
-        fatal("\"--css\" expects a file name");
+        fatal("Option \"--css\" expects a file name.");
       }
       FILE *css            = fopen(optarg, "r");
       if (!css) {
@@ -1003,6 +1006,9 @@ static void parseArgs(int argc, char * const argv[]) {
       logSetLogLevel(verbosity);
     } else if (!idx--) {
       // Static file
+      if (!optarg || !*optarg) {
+	    fatal("Option \"--static-file\" expects an argument.");
+      }
       char *ptr, *path, *file;
       if ((ptr             = strchr(optarg, ':')) == NULL) {
         fatal("Syntax error in static-file definition \"%s\".", optarg);
@@ -1021,11 +1027,14 @@ static void parseArgs(int argc, char * const argv[]) {
         fatal("Duplicate --group option.");
       }
       if (!optarg || !*optarg) {
-        fatal("\"--group\" expects a group name.");
+        fatal("Option \"--group\" expects a group name.");
       }
       runAsGroup           = parseGroupArg(optarg, NULL);
     } else if (!idx--) {
       // Linkify
+      if (!optarg || !*optarg) {
+        fatal("Option \"--linkify\" expects an argument.");
+      }
       if (!strcmp(optarg, "none")) {
         linkifyURLs        = 0;
       } else if (!strcmp(optarg, "normal")) {
@@ -1066,11 +1075,14 @@ static void parseArgs(int argc, char * const argv[]) {
         fatal("Cannot specifiy a port for CGI operation");
       }
       if (!optarg || *optarg < '0' || *optarg > '9') {
-        fatal("\"--port\" expects a port number.");
+        fatal("Option \"--port\" expects a port number.");
       }
       port = strtoint(optarg, 1, 65535);
     } else if (!idx--) {
       // Service
+      if (!optarg || !*optarg) {
+        fatal("Option \"--service\" expects an argument.");
+      }
       struct Service *service;
       service              = newService(optarg);
       if (getRefFromHashMap(serviceTable, service->path)) {
@@ -1103,13 +1115,13 @@ static void parseArgs(int argc, char * const argv[]) {
         fatal("Duplicate --user option.");
       }
       if (!optarg || !*optarg) {
-        fatal("\"--user\" expects a user name.");
+        fatal("Option \"--user\" expects a user name.");
       }
       runAsUser            = parseUserArg(optarg, NULL);
     } else if (!idx--) {
       // User CSS
       if (!optarg || !*optarg) {
-        fatal("\"--user-css\" expects a list of styles sheets and labels");
+        fatal("Option \"--user-css\" expects a list of styles sheets and labels");
       }
       parseUserCSS(&userCSSList, optarg);
     } else if (!idx--) {