Allow Reading from Block Devices with --force

.github/workflows/generic-dev.yml

@@ -30,6 +30,9 @@ jobs:
 
   test:
     runs-on: ubuntu-latest
+    env:
+      DEVNULLRIGHTS: 1
+      READFROMBLOCKDEVICE: 1
     steps:
     - uses: actions/checkout@v2
     - name: make test

programs/fileio.c

@@ -324,6 +324,7 @@ struct FIO_prefs_s {
     int excludeCompressedFiles;
     int patchFromMode;
     int contentSize;
+    int allowBlockDevices;
 };
 
 /*-*************************************
@@ -384,6 +385,7 @@ FIO_prefs_t* FIO_createPreferences(void)
     ret->testMode = 0;
     ret->literalCompressionMode = ZSTD_lcm_auto;
     ret->excludeCompressedFiles = 0;
+    ret->allowBlockDevices = 0;
     return ret;
 }
 
@@ -451,6 +453,8 @@ void FIO_setNbWorkers(FIO_prefs_t* const prefs, int nbWorkers) {
 
 void FIO_setExcludeCompressedFile(FIO_prefs_t* const prefs, int excludeCompressedFiles) { prefs->excludeCompressedFiles = excludeCompressedFiles; }
 
+void FIO_setAllowBlockDevices(FIO_prefs_t* const prefs, int allowBlockDevices) { prefs->allowBlockDevices = allowBlockDevices; }
+
 void FIO_setBlockSize(FIO_prefs_t* const prefs, int blockSize) {
     if (blockSize && prefs->nbWorkers==0)
         DISPLAYLEVEL(2, "Setting block size is useless in single-thread mode \n");
@@ -593,11 +597,12 @@ static int FIO_removeFile(const char* path)
 }
 
 /** FIO_openSrcFile() :
- *  condition : `srcFileName` must be non-NULL.
+ *  condition : `srcFileName` must be non-NULL. `prefs` may be NULL.
  * @result : FILE* to `srcFileName`, or NULL if it fails */
-static FILE* FIO_openSrcFile(const char* srcFileName)
+static FILE* FIO_openSrcFile(const FIO_prefs_t* const prefs, const char* srcFileName)
 {
     stat_t statbuf;
+    int allowBlockDevices = prefs != NULL ? prefs->allowBlockDevices : 0;
     assert(srcFileName != NULL);
     if (!strcmp (srcFileName, stdinmark)) {
         DISPLAYLEVEL(4,"Using stdin for input \n");
@@ -613,6 +618,7 @@ static FILE* FIO_openSrcFile(const char* srcFileName)
 
     if (!UTIL_isRegularFileStat(&statbuf)
      && !UTIL_isFIFOStat(&statbuf)
+     && !(allowBlockDevices && UTIL_isBlockDevStat(&statbuf))
     ) {
         DISPLAYLEVEL(1, "zstd: %s is not a regular file -- ignored \n",
                         srcFileName);
@@ -1708,7 +1714,7 @@ FIO_compressFilename_srcFile(FIO_ctx_t* const fCtx,
         return 0;
     }
 
-    ress.srcFile = FIO_openSrcFile(srcFileName);
+    ress.srcFile = FIO_openSrcFile(prefs, srcFileName);
     if (ress.srcFile == NULL) return 1;   /* srcFile could not be opened */
 
     result = FIO_compressFilename_dstFile(fCtx, prefs, ress, dstFileName, srcFileName, compressionLevel);
@@ -2571,7 +2577,7 @@ static int FIO_decompressSrcFile(FIO_ctx_t* const fCtx, FIO_prefs_t* const prefs
         return 1;
     }
 
-    srcFile = FIO_openSrcFile(srcFileName);
+    srcFile = FIO_openSrcFile(prefs, srcFileName);
     if (srcFile==NULL) return 1;
     ress.srcBufferLoaded = 0;
 
@@ -2921,7 +2927,7 @@ static InfoError
 getFileInfo_fileConfirmed(fileInfo_t* info, const char* inFileName)
 {
     InfoError status;
-    FILE* const srcFile = FIO_openSrcFile(inFileName);
+    FILE* const srcFile = FIO_openSrcFile(NULL, inFileName);
     ERROR_IF(srcFile == NULL, info_file_error, "Error: could not open source file %s", inFileName);
 
     info->compressedSize = UTIL_getFileSize(inFileName);

programs/fileio.h

@@ -103,6 +103,7 @@ void FIO_setLiteralCompressionMode(
 void FIO_setNoProgress(unsigned noProgress);
 void FIO_setNotificationLevel(int level);
 void FIO_setExcludeCompressedFile(FIO_prefs_t* const prefs, int excludeCompressedFiles);
+void FIO_setAllowBlockDevices(FIO_prefs_t* const prefs, int allowBlockDevices);
 void FIO_setPatchFromMode(FIO_prefs_t* const prefs, int value);
 void FIO_setContentSize(FIO_prefs_t* const prefs, int value);
 

programs/util.c

@@ -269,6 +269,17 @@ int UTIL_isFIFOStat(const stat_t* statbuf)
     return 0;
 }
 
+/* UTIL_isBlockDevStat : distinguish named pipes */
+int UTIL_isBlockDevStat(const stat_t* statbuf)
+{
+/* macro guards, as defined in : https://linux.die.net/man/2/lstat */
+#if PLATFORM_POSIX_VERSION >= 200112L
+    if (S_ISBLK(statbuf->st_mode)) return 1;
+#endif
+    (void)statbuf;
+    return 0;
+}
+
 int UTIL_isLink(const char* infilename)
 {
 /* macro guards, as defined in : https://linux.die.net/man/2/lstat */

programs/util.h

@@ -143,6 +143,7 @@ int UTIL_setFileStat(const char* filename, const stat_t* statbuf);
 int UTIL_isRegularFileStat(const stat_t* statbuf);
 int UTIL_isDirectoryStat(const stat_t* statbuf);
 int UTIL_isFIFOStat(const stat_t* statbuf);
+int UTIL_isBlockDevStat(const stat_t* statbuf);
 U64 UTIL_getFileSizeStat(const stat_t* statbuf);
 
 /**

programs/zstd.1

@@ -1,5 +1,7 @@
+.\" generated with Ronn/v0.7.3
+.\" http://github.com/rtomayko/ronn/tree/0.7.3
 .
-.TH "ZSTD" "1" "March 2021" "zstd 1.4.9" "User Commands"
+.TH "ZSTD" "1" "May 2021" "zstd 1.4.10" "User Commands"
 .
 .SH "NAME"
 \fBzstd\fR \- zstd, zstdmt, unzstd, zstdcat \- Compress or decompress \.zst files
@@ -156,7 +158,7 @@ This is also used during compression when using with \-\-patch\-from=\. In this
 \fB\-o FILE\fR: save result into \fBFILE\fR
 .
 .IP "\(bu" 4
-\fB\-f\fR, \fB\-\-force\fR: disable input and output checks\. Allows overwriting existing files, input from console, output to stdout, operating on links, etc\.
+\fB\-f\fR, \fB\-\-force\fR: disable input and output checks\. Allows overwriting existing files, input from console, output to stdout, operating on links, block devices, etc\.
 .
 .IP "\(bu" 4
 \fB\-c\fR, \fB\-\-stdout\fR: force write to standard output, even if it is the console

programs/zstd.1.md

@@ -202,7 +202,7 @@ the last one takes effect.
     save result into `FILE`
 * `-f`, `--force`:
     disable input and output checks. Allows overwriting existing files, input
-    from console, output to stdout, operating on links, etc.
+    from console, output to stdout, operating on links, block devices, etc.
 * `-c`, `--stdout`:
     force write to standard output, even if it is the console
 * `--[no-]sparse`:

programs/zstdcli.c

@@ -148,7 +148,8 @@ static void usage(FILE* f, const char* programName)
     DISPLAY_F(f, " -D DICT: use DICT as Dictionary for compression or decompression \n");
     DISPLAY_F(f, " -o file: result stored into `file` (only 1 output file) \n");
     DISPLAY_F(f, " -f     : disable input and output checks. Allows overwriting existing files,\n");
-    DISPLAY_F(f, "          input from console, output to stdout, operating on links, etc.\n");
+    DISPLAY_F(f, "          input from console, output to stdout, operating on links,\n");
+    DISPLAY_F(f, "          block devices, etc.\n");
     DISPLAY_F(f, "--rm    : remove source file(s) after successful de/compression \n");
     DISPLAY_F(f, " -k     : preserve source file(s) (default) \n");
     DISPLAY_F(f, " -h/-H  : display help/long help and exit \n");
@@ -724,6 +725,7 @@ int main(int const argCount, const char* argv[])
 {
     int argNb,
         followLinks = 0,
+        allowBlockDevices = 0,
         forceStdin = 0,
         forceStdout = 0,
         hasStdout = 0,
@@ -838,7 +840,7 @@ int main(int const argCount, const char* argv[])
                 if (!strcmp(argument, "--compress")) { operation=zom_compress; continue; }
                 if (!strcmp(argument, "--decompress")) { operation=zom_decompress; continue; }
                 if (!strcmp(argument, "--uncompress")) { operation=zom_decompress; continue; }
-                if (!strcmp(argument, "--force")) { FIO_overwriteMode(prefs); forceStdin=1; forceStdout=1; followLinks=1; continue; }
+                if (!strcmp(argument, "--force")) { FIO_overwriteMode(prefs); forceStdin=1; forceStdout=1; followLinks=1; allowBlockDevices=1; continue; }
                 if (!strcmp(argument, "--version")) { printVersion(); CLEAN_RETURN(0); }
                 if (!strcmp(argument, "--help")) { usage_advanced(programName); CLEAN_RETURN(0); }
                 if (!strcmp(argument, "--verbose")) { g_displayLevel++; continue; }
@@ -1024,7 +1026,7 @@ int main(int const argCount, const char* argv[])
                 case 'D': argument++; NEXT_FIELD(dictFileName); break;
 
                     /* Overwrite */
-                case 'f': FIO_overwriteMode(prefs); forceStdin=1; forceStdout=1; followLinks=1; argument++; break;
+                case 'f': FIO_overwriteMode(prefs); forceStdin=1; forceStdout=1; followLinks=1; allowBlockDevices=1; argument++; break;
 
                     /* Verbose mode */
                 case 'v': g_displayLevel++; argument++; break;
@@ -1331,6 +1333,7 @@ int main(int const argCount, const char* argv[])
     FIO_setNbFilesTotal(fCtx, (int)filenames->tableSize);
     FIO_determineHasStdinInput(fCtx, filenames);
     FIO_setNotificationLevel(g_displayLevel);
+    FIO_setAllowBlockDevices(prefs, allowBlockDevices);
     FIO_setPatchFromMode(prefs, patchFromDictFileName != NULL);
     if (memLimit == 0) {
         if (compressionParams.windowLog == 0) {

tests/playTests.sh

@@ -459,6 +459,22 @@ if [ -n "$DEVNULLRIGHTS" ] ; then
     ls -las $INTOVOID | grep "rw-rw-rw-"
 fi
 
+if [ -n "$READFROMBLOCKDEVICE" ] ; then
+    # This creates a temporary block device, which is only possible on unix-y
+    # systems, is somewhat invasive, and requires sudo. For these reasons, you
+    # have to specifically ask for this test.
+    println "\n===> checking that zstd can read from a block device"
+    datagen -g65536 > tmp.img
+    sudo losetup -fP tmp.img
+    LOOP_DEV=$(losetup -a | grep 'tmp\.img' | cut -f1 -d:)
+    [ -z "$LOOP_DEV" ] && die "failed to get loopback device"
+    sudoZstd $LOOP_DEV -c > tmp.img.zst && die "should fail without -f"
+    sudoZstd -f $LOOP_DEV -c > tmp.img.zst
+    zstd -d tmp.img.zst -o tmp.img.copy
+    sudo losetup -d $LOOP_DEV
+    $DIFF -s tmp.img tmp.img.copy || die "round trip failed"
+    rm -f tmp.img tmp.img.zst tmp.img.copy
+fi
 
 println "\n===>  compress multiple files into an output directory, --output-dir-flat"
 println henlo > tmp1