Makefile

@@ -25,15 +25,8 @@ install: writeimg
 	install -m 0755 $< $(DESTDIR)$(PREFIX)/bin/$<
 	install -m 0644 $<.1 $(DESTDIR)$(PREFIX)/share/man/man1/$<.1
 
-# Note that this bypasses PREFIX, since
-# bash does not source /usr/local by default
-install_bash: writeimg_completion_bash.sh
-	install -d $(DESTDIR)/etc/bash_completion.d
-	install -m 0644 $< $(DESTDIR)/etc/bash_completion.d/$<
-
 uninstall:
 	rm -f $(DESTDIR)$(PREFIX)/bin/writeimg
 	rm -f $(DESTDIR)$(PREFIX)/share/man/man1/writeimg.1
-	rm -f $(DESTDIR)/etc/bash_completion.d/writeimg*
 
 .PHONY: clean install uninstall

README.md

@@ -1,17 +1,13 @@
-# WriteIMG Image Writer
+# Simple dd-like image writer with additional security checks.
 
-WriteIMG is a simple dd-like image writer with additional security checks for
+This tool verifies your image automatically. The block size is currently set to
-Linux and soon FreeBSD. It tells you what you're about to do and warns you
+1 MiB, which should be enough to avoid trouble.
-about potential problems before they occur. It also features automatic image
-verifications, and uses a suitable block size for fast and gentle writing.  
-
-Say goodbye to fried flash and overwritten bootloaders, no more footguns!
 
 ```
-WriteIMG v0.2.3, Rev. d02fc5f
+writeimg v0.2.0, Rev. 5323932-dirty
 In honor of SwePwnage - the OG disk destroyer
 Copyright (C) 2026 Imbus, BSD-2-Clause
-Build date: 2026-02-21
+Build date: 2026-02-07
 
 Usage:
    writeimg [-v] -d <device> <file.img>
@@ -21,18 +17,12 @@ Args:
    -v                  Verify only
    -d device           Target block device
    -h, --help          Print this help message
-   -n, --noconfirm     Do not ask for permission
+   -n, --noconfirm     Do not ask for premission
    -V, --version       Print version
 ```
 
-We also provide a manpage, which targets OpenBSD-level quality. Incorrect or
-outdated information is a bug.
-
 ## Testing
 
-For testing, there is a shell script "test.sh" included. It sets up a block dev
-and writes (and verifies) a bunch of nonsense to it. It boils down to:
-
 ```
 dd if=/dev/zero of=./disk.img bs=1M count=1024
 losetup -fP ./disk.img
@@ -40,75 +30,6 @@ losetup -a
 losedup -d /dev/loop0
 ```
 
-Writes to a regular files is not currently in scope, although it would simplify
-testing.
-
-## Design Considerations
-
-Most of the sanity checking is currently highly Linux specific. We should
-prefer general/posix solutions that reach **at least** FreeBSD, preferably
-OpenBSD and Solaris as well. FreeBSD did implement procfs, but its a Linux-ism
-and it has since been deprecated. I would prefer not to turn this rather simple
-code into macro-mozaic, as i've seen other similar projects do. After all, this
-is just a juiced-up dd-rewrite at its core.  
-
-**Apple products are unsupported.** Im simply not interested in ensuring
-compatibility with a walled-garden ecosystem. If *you* are, we can change that.  
-
-At the time of writing, my FreeBSD server is down for maintenance, which means
-all of my development and testing is focused on AMD64, AArch64 and AArch32
-Linux.  
-
-In the setup phase of the program, we can absolutely afford to do lots of
-sanity checking via syscalls. Between each block write, we flush the disk
-buffers. These flushes are larger (1 MiB when buffer is full) than the sector
-size (often 4k or 64k) of the flash, so as far as i know, this is a gentle way
-to write flash, and should not incur any significant performance overhead. 1
-MiB is also a multiple of the most common sector sizes. We could write it all
-with no flushing, but that would mean the progress indicator will measure
-buffered writes, which is useless.  
-
-It should be possible to induce optimal block size, but this idea has not been
-explored yet.  
-
-Currently when verifying the written data, we read from both the input file and
-the output block device and do a byte-by-byte comparison. A CRC32 is also
-calculated in the first pass of the input file read. In the second pass (the
-verification stage), we calculate the CRC32 of the block device data and
-compare that to our previous result. **This means that we currently use two
-separate methods of verification**. The program allocates **two** separate
-buffers in the startup phase for comparisons. This will change in the coming
-releases, and we will rely only on the CRC.  
-
-De-allocation is handled in the interrupt vector as well as in the 'sad-paths',
-but ultimately this program can be regarded as samurai-principled. We try to
-handle deallocation, but exit on failure and let the kernel handle the rest.  
-
-The use of a crypto-grade checksumming algorithm was considered, but was
-ultimately rejected in favour of a lookup based CRC32. Its simpler, faster and
-easier to understand (See: [crc32.h](./crc32.h)). We may include a compile-time
-option to disable the lookup table to reduce size for really small targets, but
-we speculate that those targets are already satisfied with busybox-dd.  
-
-We also considered using libudev or any of its analogues, to determine the type
-of block device (spinning or flash), but my somewhat inconclusive research
-indicates that it does not include functionality to determine the medium type
-(usb/sd/sata), which is ultimately what i would like to warn the user about.
-The libudev library is also Linux specific.  
-
-We also need completion scripts for the most common shells. This includes csh,
-bash and zsh. Should be easy enough when we set our minds to it.  
-
-See:
- - `grep -nE 'BLK[A-Za-z0-9]+' /usr/include/linux/fs.h`  
-   In particular, we're interested in BLKGETSIZE64 and BLKFLSBUF for now.
-
-We can read the device info from:
- - /sys/class/block/[name]/*
-Like:
- - /sys/class/block/[name]/device/model
- - /sys/class/block/[name]/size
-
 ## Inspiration
 
 See:

test.sh

@@ -4,17 +4,13 @@ set -e
 # set -x # For debugging
 
 # If you ever mess this up:
-#  $ mknod /dev/loop-control c 10 237
+#  $ sudo mknod /dev/loop-control c 10 237
-#  $ chmod 600 /dev/loop-control
+#  $ sudo chmod 600 /dev/loop-control
-#  $ chown root:root /dev/loop-control
+#  $ sudo chown root:root /dev/loop-control
 #
 # For cleanup:
-#  $ find /dev -maxdepth 1 -type b -name 'loop[0-9]*' -exec rm -f {} \;
+#  $ sudo find /dev -maxdepth 1 -type b -name 'loop[0-9]*' -exec rm -f {} \;
 
-if [ "$(id -u)" -ne 0 ]; then
-    echo "Run as root. We need permissions to write and setup a loop device."
-    exit 1
-fi
 
 DISKFILE="/tmp/disk.img"
 BINFILE="/tmp/file.bin"
@@ -26,9 +22,9 @@ echo "Using device: ${LOOPDEV}"
 cleanup() {
     echo "Cleaning up..."
     set +e -x
-    losetup -d ${LOOPDEV}
+    sudo losetup -d ${LOOPDEV}
-    rm ${LOOPDEV}
+    sudo rm ${LOOPDEV}
-    rm ${BINFILE} ${DISKFILE}
+    sudo rm ${BINFILE} ${DISKFILE}
 }
 
 trap cleanup EXIT INT TERM
@@ -40,31 +36,28 @@ if losetup ${LOOPDEV} >/dev/null 2>&1; then
 fi
 
 if [ ! -f ${DISKFILE} ]; then
-    echo "Creating ${DISKFILE}"
     dd if=/dev/zero of=${DISKFILE} bs=1M count=256
 fi
 
 if [ ! -f ${BINFILE} ]; then
-    echo "Creating ${BINFILE}"
     dd if=/dev/urandom of=${BINFILE} bs=1M count=64
 fi
 
 if [ ! -e ${LOOPDEV} ]; then
-    mknod ${LOOPDEV} b 7 ${LOOPNUM} # busybox needs this
+    sudo losetup ${LOOPDEV} ${DISKFILE}
-    losetup ${LOOPDEV} ${DISKFILE}
 fi
 
-./writeimg -nd ${LOOPDEV} ${BINFILE}
+sudo ./writeimg -nd ${LOOPDEV} ${BINFILE}
-./writeimg -vnd ${LOOPDEV} ${BINFILE}
+sudo ./writeimg -vnd ${LOOPDEV} ${BINFILE}
 
-./writeimg -nd ${LOOPDEV} ./writeimg
+sudo ./writeimg -nd ${LOOPDEV} ./writeimg
-./writeimg -vnd ${LOOPDEV} ./writeimg
+sudo ./writeimg -vnd ${LOOPDEV} ./writeimg
 
-./writeimg -nd ${LOOPDEV} ./LICENSE
+sudo ./writeimg -nd ${LOOPDEV} ./LICENSE
-./writeimg -vnd ${LOOPDEV} ./LICENSE
+sudo ./writeimg -vnd ${LOOPDEV} ./LICENSE
 
 # Redirect this to avoid confusion
-! ./writeimg -vnd ${LOOPDEV} ./crc32.h 2>/dev/null
+! sudo ./writeimg -vnd ${LOOPDEV} ./crc32.h 2>/dev/null
 
 GREEN="\e[32m"
 RESET="\e[0m"

writeimg.c

@@ -72,7 +72,7 @@ const char help[] =
     "   -v                  Verify only\n"
     "   -d device           Target block device\n"
     "   -h, --help          Print this help message\n"
-    "   -n, --noconfirm     Do not ask for permission\n"
+    "   -n, --noconfirm     Do not ask for premission\n"
     "   -V, --version       Print version\n"
     "\0";
 // clang-format on
@@ -278,11 +278,7 @@ int main(int argc, char *argv[]) {
             exit(EXIT_FAILURE);
         }
 
-#ifdef __GLIBC__
         if (ioctl(fd, BLKGETSIZE64, &device_size) < 0) {
-#else /* With musl, ioctl's take ints, kheaders provide unsigned longs. Passes tests. */
-        if (ioctl(fd, (int)BLKGETSIZE64, &device_size) < 0) {
-#endif
             perror("ioctl");
             close(fd);
             exit(EXIT_FAILURE);

writeimg_completion_bash.sh

@@ -1,25 +0,0 @@
-_writeimg_completion() {
-    local cur prev opts
-
-    cur="${COMP_WORDS[COMP_CWORD]}"
-    prev="${COMP_WORDS[COMP_CWORD-1]}"
-
-    opts="-v -d -h --help -n --noconfirm -V --version"
-
-    # Devices
-    if [[ "$prev" == "-d" ]]; then
-        COMPREPLY=( $(compgen -W "$(ls -d /dev/sd* /dev/nvme* /dev/mmcblk* 2>/dev/null)" -- "$cur") )
-        return 0
-    fi
-
-    # Flags
-    if [[ "$cur" != -* ]]; then
-        COMPREPLY=( $(compgen -f -- "$cur") )
-        return 0
-    fi
-
-    # Files
-    COMPREPLY=( $(compgen -W "$opts" -- "$cur") )
-}
-
-complete -F _writeimg_completion writeimg