From b73bf969e6538e03cc0d9761a62f3ffbd494eb6c Mon Sep 17 00:00:00 2001
From: Jakob Kaivo <jkk@ung.org>
Date: Thu, 1 Aug 2019 10:10:52 -0400
Subject: initial commit

---
 .gitignore |  2 ++
 Makefile   |  6 ++++++
 README.md  | 58 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 runcode.c  | 38 ++++++++++++++++++++++++++++++++++++++
 4 files changed, 103 insertions(+), 1 deletion(-)
 create mode 100644 .gitignore
 create mode 100644 Makefile
 create mode 100644 runcode.c

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..d995580
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+runcode
+*.o
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..5544d3a
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,6 @@
+.POSIX:
+
+runcode: runcode.c
+
+clean:
+	rm -f *.o runcode
diff --git a/README.md b/README.md
index c108733..7d8ba53 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,59 @@
 # runcode
 
-execute raw binary code from a file
\ No newline at end of file
+execute raw binary code from a file
+
+# Synopsis
+
+`runcode file`
+
+# Description
+
+The `runcode` utility loads an arbitrary binary file into memory and attempts
+to execute it. This is useful for testing shellcode used in penetration
+testing.
+
+# Options
+
+None.
+
+# Operands
+
+`file` A file containing executable instructions.
+
+# STDIN
+
+Not used by `runcode` itself. May be used by the loaded program.
+
+# Input Files
+
+The input file must be contain valid executable instructions appropriate
+to architecture `runcode` is being executed on.
+
+# STDOUT
+
+Not used by `runcode` itself. May be used by the loaded program.
+
+# STDERR
+
+Used for diagnostic messages.
+
+# Output Files
+
+None.
+
+# Extended Description
+
+None.
+
+# Exit Status
+
+0	Successful completion.
+>0	An error occurred.
+
+# Consequence of Errors
+
+If the file specified cannot be opened for reading or mapped for execution,
+a diagnostic message will be printed to standard error. Behavior is undefined
+if the file specified does not contain an executable instruction at its first
+byte.
+
diff --git a/runcode.c b/runcode.c
new file mode 100644
index 0000000..5a69ea1
--- /dev/null
+++ b/runcode.c
@@ -0,0 +1,38 @@
+#define _POSIX_C_SOURCE 199309
+#include <fcntl.h>
+#include <stdio.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+
+int main(int argc, char *argv[])
+{
+	if (argc != 2) {
+		fprintf(stderr, "Usage: %s file\n", argv[0]);
+		return 1;
+	}
+
+	int fd = open(argv[1], O_RDONLY);
+	if (fd == -1) {
+		perror("open");
+		return 1;
+	}
+
+	struct stat st;
+	if (fstat(fd, &st) == -1) {
+		perror("fstat");
+		return 1;
+	}
+
+	void *code = mmap(NULL, st.st_size, PROT_EXEC | PROT_READ | PROT_WRITE,
+		MAP_PRIVATE, fd, 0);
+
+	if (code == MAP_FAILED) {
+		perror("mmap");
+		return 1;
+	}
+
+	void (*fn)(void) = (void (*)(void))code;
+	fn();
+
+	return 0;
+}
-- 
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