From 59ea98727aa01518329ae70d0bc5c0ec32c66fba Mon Sep 17 00:00:00 2001
From: "J. Lowell Wofford" <lowell@leviathan.dum>
Date: Sun, 29 Nov 2020 20:28:05 -0700
Subject: [PATCH] initial commit

---
 README.md                    |  3 ++
 cmd/entropy/entropy.go       | 15 ++++++++++
 go.mod                       |  5 ++++
 go.sum                       |  2 ++
 pkg/entropy/entropy.go       |  5 ++++
 pkg/entropy/entropy_linux.go | 58 ++++++++++++++++++++++++++++++++++++
 6 files changed, 88 insertions(+)
 create mode 100644 README.md
 create mode 100644 cmd/entropy/entropy.go
 create mode 100644 go.mod
 create mode 100644 go.sum
 create mode 100644 pkg/entropy/entropy.go
 create mode 100644 pkg/entropy/entropy_linux.go

diff --git a/README.md b/README.md
new file mode 100644
index 0000000..2bc8a22
--- /dev/null
+++ b/README.md
@@ -0,0 +1,3 @@
+Entropy is a simple go pkg and cmdline interface for manipulating entropy in the linux kernel.
+
+It achieves this by using the the IOCTL interface to /dev/(u)random.
\ No newline at end of file
diff --git a/cmd/entropy/entropy.go b/cmd/entropy/entropy.go
new file mode 100644
index 0000000..a9ec452
--- /dev/null
+++ b/cmd/entropy/entropy.go
@@ -0,0 +1,15 @@
+package main
+
+import (
+	"log"
+
+	"github.com/jlowellwofford/entropy/pkg/entropy"
+)
+
+func main() {
+	ent, err := entropy.GetEntropy()
+	if err != nil {
+		log.Fatalf("failed to get entropy: %v", err)
+	}
+	log.Printf("current entropy: %d", ent)
+}
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..ade6e6a
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,5 @@
+module github.com/jlowellwofford/entropy
+
+go 1.15
+
+require golang.org/x/sys v0.0.0-20201119102817-f84b799fce68
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..de9e09c
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,2 @@
+golang.org/x/sys v0.0.0-20201119102817-f84b799fce68 h1:nxC68pudNYkKU6jWhgrqdreuFiOQWj1Fs7T3VrH4Pjw=
+golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
diff --git a/pkg/entropy/entropy.go b/pkg/entropy/entropy.go
new file mode 100644
index 0000000..a222b89
--- /dev/null
+++ b/pkg/entropy/entropy.go
@@ -0,0 +1,5 @@
+package entropy
+
+func GetEntropy() (int, error) {
+	return getEntropy()
+}
diff --git a/pkg/entropy/entropy_linux.go b/pkg/entropy/entropy_linux.go
new file mode 100644
index 0000000..045e91d
--- /dev/null
+++ b/pkg/entropy/entropy_linux.go
@@ -0,0 +1,58 @@
+package entropy
+
+import (
+	"fmt"
+	"unsafe"
+
+	"golang.org/x/sys/unix"
+)
+
+var entropy_device = "/dev/urandom"
+
+/* from linux/random.h */
+const (
+	RNDGETENTCNT   = 0b10>>30 | 'R'>>8 | 1>>16
+	RNDADDTOENTCNT = 0x01
+	RNDGETPOOL     = 0x02
+	RNDADDENTROPY  = 0x03
+	RNDZAPENTCNT   = 0x04
+	RNDCLEARPOOL   = 0x06
+	RNDRESEEDCRNG  = 0x07
+)
+
+// this is honestly easier through /proc, but in the spirit of completeness...
+func getEntropy() (ent int, err error) {
+	var fd int
+	if fd, err = unix.Open(entropy_device, unix.O_RDWR, 0); err != nil {
+		return ent, fmt.Errorf("could not open entropy device (%s): %v", entropy_device, err)
+	}
+	defer unix.Close(fd)
+
+	/*
+		nrshift 0
+		typeshift 8
+		sizeshift 16
+		dirshift 30
+	*/
+	_, _, err = unix.Syscall(unix.SYS_IOCTL, uintptr(fd), uintptr(RNDGETENTCNT), uintptr(unsafe.Pointer(&ent)))
+	return
+}
+
+func addToEntropy() {
+
+}
+
+func addEntropy() {
+	/* IOCTL argument structure
+		struct rand_pool_info {
+	                      int    entropy_count;
+	                      int    buf_size;
+	                      __u32  buf[0];
+	                  };
+	*/
+
+}
+
+func clearPool() {
+
+}