Add SIGIO signal to fill fake /dev/urandom (#310)

CHANGELOG.md

@@ -38,6 +38,7 @@
 * Check mask size in XISelectEvents
 * XI_RawMotion now uses raw inputs
 * Track handles of savefiles
+* Fill asynchronously fake /dev/urandom for games that read a large number of bytes (#310)
 
 ## [1.3.5] - 2019-11-26
 ### Added

src/library/Makefile.am

@@ -87,6 +87,7 @@ libtas_so_SOURCES = \
     fileio/SaveFile.cpp \
     fileio/SaveFileList.cpp \
     fileio/stdiowrappers.cpp \
+    fileio/URandom.cpp \
     inputs/evdev.cpp \
     inputs/inputevents.cpp \
     inputs/inputs.cpp \

src/library/fileio/URandom.cpp

@@ -0,0 +1,111 @@
+/*
+    Copyright 2015-2020 Clément Gallet <clement.gallet@ens-lyon.org>
+
+    This file is part of libTAS.
+
+    libTAS is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    libTAS is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with libTAS.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "URandom.h"
+
+#include "FileHandleList.h"
+#include "../logging.h"
+#include <fcntl.h>
+#include <unistd.h> // getpid()
+
+namespace libtas {
+
+static int readfd = -1;
+static int writefd = -1;
+static char* datestr = nullptr;
+static FILE* stream = nullptr;
+
+static void urandom_handler(int signum)
+{
+    /* TODO: write a simple PRNG which is seeded by shared_config.initial_time_sec
+     * instead of outputting it directly as a string.
+     */
+    debuglogstdio(LCF_FILEIO | LCF_RANDOM, "Filling urandom fd");
+    if (!datestr) {
+        time_t tsec = static_cast<time_t>(shared_config.initial_time_sec);
+        datestr = asctime(gmtime(&tsec));
+    }
+
+    /* Fill the pipe with data from initial time */
+    int err = write(writefd, datestr, strlen(datestr));
+    while (err != -1) {
+        err = write(writefd, datestr, strlen(datestr));
+    }
+}
+
+int urandom_create_fd()
+{
+    debuglogstdio(LCF_FILEIO | LCF_RANDOM, "Open /dev/urandom");
+
+    if (readfd == -1) {
+        std::pair<int, int> fds = FileHandleList::createPipe(O_NONBLOCK);
+        readfd = fds.first;
+        writefd = fds.second;
+
+        /* Set the pipe size to some small value, because we won't need much.
+         * It should be at least 2*page_size, because on Linux a pipe is
+         * considered writeable if at least page_size can be written.
+         */
+        MYASSERT(fcntl(writefd, F_SETPIPE_SZ, 2*4096) != -1);
+
+        /* Fill the pipe */
+        urandom_handler(0);
+
+        GlobalNative gn;
+
+        /* Add async signal for when the pipe is writeable */
+        MYASSERT(fcntl(writefd, F_SETOWN, getpid()) != -1);
+        MYASSERT(fcntl(writefd, F_SETSIG, 0) != -1);
+        MYASSERT(fcntl(writefd, F_SETFL, O_ASYNC | O_NONBLOCK) != -1);
+
+        /* Unblock SIGIO signal */
+        sigset_t mask;
+        sigemptyset(&mask);
+        sigaddset(&mask, SIGIO);
+        MYASSERT(pthread_sigmask(SIG_UNBLOCK, &mask, nullptr) == 0);
+
+        /* Add signal handler for SIGIO signal */
+        struct sigaction sigio;
+        sigfillset(&sigio.sa_mask);
+        sigio.sa_handler = urandom_handler;
+        MYASSERT(sigaction(SIGIO, &sigio, nullptr) == 0)
+    }
+
+    debuglog(LCF_FILEIO | LCF_RANDOM, "Return fd ", readfd);
+    return readfd;
+}
+
+int urandom_get_fd() {
+    return readfd;
+}
+
+FILE* urandom_create_file() {
+    if (!stream) {
+        int readfd = urandom_create_fd();
+        stream = fdopen(readfd, "r");
+        setvbuf(stream, nullptr, _IONBF, 0);
+    }
+    return stream;
+}
+
+FILE* urandom_get_file() {
+    return stream;
+}
+
+}

src/library/fileio/URandom.h

@@ -0,0 +1,41 @@
+/*
+    Copyright 2015-2020 Clément Gallet <clement.gallet@ens-lyon.org>
+
+    This file is part of libTAS.
+
+    libTAS is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    libTAS is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with libTAS.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef LIBTAS_URANDOM_H_INCLUDED
+#define LIBTAS_URANDOM_H_INCLUDED
+
+#include <cstdio>
+
+namespace libtas {
+
+/* Creates a fd implementing our own deterministic /dev/urandom */
+int urandom_create_fd();
+
+/* Returns that fd, or -1 if not created */
+int urandom_get_fd();
+
+/* Creates a FILE* stream containing the above fd */
+FILE* urandom_create_file();
+
+/* Returns the /dev/urandom FILE* stream */
+FILE* urandom_get_file();
+
+}
+
+#endif

src/library/fileio/posixiowrappers.cpp

@@ -23,6 +23,7 @@
 #include "../hook.h"
 #include "SaveFileList.h"
 #include "FileHandleList.h"
+#include "URandom.h"
 #include "../GlobalState.h"
 #include "../inputs/jsdev.h"
 #include "../inputs/evdev.h"
@@ -75,27 +76,7 @@ int open (const char *file, int oflag, ...)
     int fd = 0;
 
     if ((strcmp(file, "/dev/urandom") == 0) || (strcmp(file, "/dev/random") == 0)) {
-        if (SaveFileList::getSaveFileFd(file) == 0) {
-            /* Create a file with memory storage (reusing the savefile code),
-             * and fill it with values from the initial time, so that, for
-             * games that use it as PRNG seed, tweaking the initial time will
-             * change the seed value.
-             */
-            fd = SaveFileList::openSaveFile(file, O_RDWR | O_TRUNC);
-
-            time_t tsec = static_cast<time_t>(shared_config.initial_time_sec);
-            char* datestr = asctime(gmtime(&tsec));
-            debuglogstdio(LCF_FILEIO, "Creating fake %s with %s", file, datestr);
-
-            write(fd, datestr, strlen(datestr));
-            char buf[256];
-            sprintf(buf, "%0*d", 255, 0);
-            write(fd, buf, 255);
-            lseek(fd, 0, SEEK_SET);
-        }
-        else {
-            fd = SaveFileList::openSaveFile(file, oflag);
-        }
+        return urandom_create_fd();
     }
 
     else if (strcmp(file, "/proc/uptime") == 0) {
@@ -175,26 +156,7 @@ int open64 (const char *file, int oflag, ...)
     int fd = 0;
 
     if ((strcmp(file, "/dev/urandom") == 0) || (strcmp(file, "/dev/random") == 0)) {
-        if (SaveFileList::getSaveFileFd(file) == 0) {
-            /* Create a file with memory storage (reusing the savefile code),
-             * and fill it with values from the initial time, so that, for
-             * games that use it as PRNG seed, tweaking the initial time will
-             * change the seed value.
-             */
-            fd = SaveFileList::openSaveFile(file, O_RDWR | O_TRUNC);
-
-            time_t tsec = static_cast<time_t>(shared_config.initial_time_sec);
-            char* datestr = asctime(gmtime(&tsec));
-            debuglogstdio(LCF_FILEIO, "Creating fake %s with %s", file, datestr);
-            write(fd, datestr, strlen(datestr));
-            char buf[256];
-            sprintf(buf, "%0*d", 255, 0);
-            write(fd, buf, 255);
-            lseek(fd, 0, SEEK_SET);
-        }
-        else {
-            fd = SaveFileList::openSaveFile(file, oflag);
-        }
+        return urandom_create_fd();
     }
 
     else if (strcmp(file, "/proc/uptime") == 0) {
@@ -391,6 +353,11 @@ int close (int fd)
 
     debuglogstdio(LCF_FILEIO, "%s call", __func__);
 
+    /* Check for urandom */
+    if (urandom_get_fd() == fd) {
+        return 0;
+    }
+
     /* Check if we must actually close the file */
     bool doClose = FileHandleList::closeFile(fd);
 

src/library/fileio/stdiowrappers.cpp

@@ -24,6 +24,7 @@
 #include "SaveFileList.h"
 #include "FileHandleList.h"
 #include "../GlobalState.h"
+#include "URandom.h"
 
 namespace libtas {
 
@@ -51,26 +52,7 @@ FILE *fopen (const char *filename, const char *modes)
     FILE* f = nullptr;
 
     if ((strcmp(filename, "/dev/urandom") == 0) || (strcmp(filename, "/dev/random") == 0)) {
-        if (SaveFileList::getSaveFileFd(filename) == 0) {
-            /* Create a file with memory storage (reusing the savefile code),
-             * and fill it with values from the initial time, so that, for
-             * games that use it as PRNG seed, tweaking the initial time will
-             * change the seed value.
-             */
-            f = SaveFileList::openSaveFile(filename, "w");
-
-            time_t tsec = static_cast<time_t>(shared_config.initial_time_sec);
-            char* datestr = asctime(gmtime(&tsec));
-            debuglogstdio(LCF_FILEIO, "Creating fake %s with %s", filename, datestr);
-            fwrite(datestr, sizeof(char), strlen(datestr), f);
-            char buf[256];
-            sprintf(buf, "%0*d", 255, 0);
-            fwrite(buf, sizeof(char), 255, f);
-            fseek(f, 0, SEEK_SET);
-        }
-        else {
-            f = SaveFileList::openSaveFile(filename, modes);
-        }
+        return urandom_create_file();
     }
 
     else if (strcmp(filename, "/proc/uptime") == 0) {
@@ -132,26 +114,7 @@ FILE *fopen64 (const char *filename, const char *modes)
     FILE* f = nullptr;
 
     if ((strcmp(filename, "/dev/urandom") == 0) || (strcmp(filename, "/dev/random") == 0)) {
-        if (SaveFileList::getSaveFileFd(filename) == 0) {
-            /* Create a file with memory storage (reusing the savefile code),
-             * and fill it with values from the initial time, so that, for
-             * games that use it as PRNG seed, tweaking the initial time will
-             * change the seed value.
-             */
-            f = SaveFileList::openSaveFile(filename, "w");
-
-            time_t tsec = static_cast<time_t>(shared_config.initial_time_sec);
-            char* datestr = asctime(gmtime(&tsec));
-            debuglogstdio(LCF_FILEIO, "Creating fake %s with %s", filename, datestr);
-            fwrite(datestr, sizeof(char), strlen(datestr), f);
-            char buf[256];
-            sprintf(buf, "%0*d", 255, 0);
-            fwrite(buf, sizeof(char), 255, f);
-            fseek(f, 0, SEEK_SET);
-        }
-        else {
-            f = SaveFileList::openSaveFile(filename, modes);
-        }
+        return urandom_create_file();
     }
 
     else if (strcmp(filename, "/proc/uptime") == 0) {
@@ -207,6 +170,11 @@ int fclose (FILE *stream)
 
     DEBUGLOGCALL(LCF_FILEIO);
 
+    /* Check for urandom */
+    if (urandom_get_file() == stream) {
+        return 0;
+    }
+
     /* Check if we must actually close the file */
     bool doClose = FileHandleList::closeFile(fileno(stream));