initial commit

README.md

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+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.

cmd/entropy/entropy.go

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+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)
+}

go.mod

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+module github.com/jlowellwofford/entropy
+
+go 1.15
+
+require golang.org/x/sys v0.0.0-20201119102817-f84b799fce68

go.sum

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+golang.org/x/sys v0.0.0-20201119102817-f84b799fce68 h1:nxC68pudNYkKU6jWhgrqdreuFiOQWj1Fs7T3VrH4Pjw=
+golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=

pkg/entropy/entropy.go

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+package entropy
+
+func GetEntropy() (int, error) {
+	return getEntropy()
+}

pkg/entropy/entropy_linux.go

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+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() {
+
+}