Write(写)

Radare can manipulate a loaded binary file in many ways. You can resize the file, move and copy/paste bytes, insert new bytes (shifting data to the end of the block or file), or simply overwrite bytes. New data may be given as a wide-string, assembler instructions, or the data may be read in from another file.

Resize the file using the r command. It accepts a numeric argument. A positive value sets a new size for the file. A negative one will truncate the file to the current seek position minus N bytes.

r 1024      ; resize the file to 1024 bytes
r -10 @ 33  ; strip 10 bytes at offset 33

Write bytes using the w command. It accepts multiple input formats like inline assembly, endian-friendly dwords, files, hexpair files, wide strings:

[0x00404888]> w?
|Usage: w[x] [str] [<file] [<<EOF] [@addr]
| w[1248][+-][n]       increment/decrement byte,word..
| w foobar             write string 'foobar'
| w0 [len]             write 'len' bytes with value 0x00
| w6[de] base64/hex    write base64 [d]ecoded or [e]ncoded string
| wa[?] push ebp       write opcode, separated by ';'
| waf file             assemble file and write bytes
| wao[?] op            modify opcode (conditional jump. nop, etc)
| wA[?] r 0            alter/modify opcode at current seek (wA?)
| wb 010203            fill current block with cyclic hexpairs
| wB[-]0xVALUE         set or unset bits with given value
| wc                   list all write changes
| wc[?][ir*?]          write cache undo/commit/reset/list (io.cache)
| wd [off] [n]         duplicate N bytes from offset to here
| we[?] [nNsxX] [arg]  extend write operations (insert vs replace)
| wf -|file            write contents of file at current offset
| wh r2                whereis/which shell command
| wm f0ff              set cyclick binary write mask hexpair
| wo[?] hex            write in block with operation. 'wo?' fmi
| wp[?] -|file         apply radare patch file. See wp? fmi
| wr 10                write 10 random bytes
| ws pstring           write 1 byte for length and then the string
| wt[f][?] file [sz]   write to file (from current seek, blocksize)
| wts host:port [sz]   send data to remote host:port via tcp://
| ww foobar            write wide string
| wx[?][fs] 9090       write two intel nops (from wxfile or wxseek)
| wv[?] eip+34         write 32-64 bit value
| wz string            write zero terminated string (like w + \x00)

Some examples:

Write Over

The wo command (write over) has many subcommands, each combines the existing data with the new data using an operator. The command is applied to the current block. Supported operators include XOR, ADD, SUB...

It is possible to implement cipher-algorithms using radare core primitives and wo. A sample session performing xor(90) + add(01, 02):

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