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add gen_constants to generate IOCTL constants; add generated file

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This commit is contained in:
J. Lowell Wofford 2020-11-29 22:21:09 -07:00
parent 59ea98727a
commit 8b10facda8
3 changed files with 54 additions and 18 deletions
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14
pkg/entropy/constants_linux.go Normal file
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@ -0,0 +1,14 @@
// generated by gen_constants.c
package entropy
const (
RNDGETENTCNT = 0x80045200
RNDADDTOENTCNT = 0x40045201
RNDGETPOOL = 0x80085202
RNDADDENTROPY = 0x40085203
RNDZAPENTCNT = 0x5204
RNDCLEARPOOL = 0x5206
RNDRESEEDCRNG = 0x5207
)

24
pkg/entropy/entropy_linux.go
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@ -2,6 +2,7 @@ package entropy
import (
"fmt"
"syscall"
"unsafe"
"golang.org/x/sys/unix"
@ -9,17 +10,6 @@ import (
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
@ -28,13 +18,11 @@ func getEntropy() (ent int, err error) {
}
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)))
var errno syscall.Errno
_, _, errno = unix.Syscall(unix.SYS_IOCTL, uintptr(fd), uintptr(RNDGETENTCNT), uintptr(unsafe.Pointer(&ent)))
if errno != 0 {
err = errno
}
return
}

34
pkg/entropy/util/gen_constants.c Normal file
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@ -0,0 +1,34 @@
// This simple program writes constants.go
// It uses the Linux headers to generate these contatns.
#include <fcntl.h>
#include <linux/random.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
const char * filename = "constants_linux.go";
int main() {
int fd;
printf("Generating constants for entropy IOCTLs.\n");
fd = open(filename, O_CREAT | O_TRUNC | O_WRONLY, 0644);
if( fd == -1 ) {
printf("Failed to open output file: %s\n", filename);
return -1;
}
dprintf(fd, "// generated by gen_constants.c\n\n");
dprintf(fd, "package entropy\n\n");
dprintf(fd, "const (\n");
dprintf(fd, "\tRNDGETENTCNT = %#x\n", RNDGETENTCNT);
dprintf(fd, "\tRNDADDTOENTCNT = %#x\n", RNDADDTOENTCNT);
dprintf(fd, "\tRNDGETPOOL = %#x\n", RNDGETPOOL);
dprintf(fd, "\tRNDADDENTROPY = %#x\n", RNDADDENTROPY);
dprintf(fd, "\tRNDZAPENTCNT = %#x\n", RNDZAPENTCNT);
dprintf(fd, "\tRNDCLEARPOOL = %#x\n", RNDCLEARPOOL);
dprintf(fd, "\tRNDRESEEDCRNG = %#x\n", RNDRESEEDCRNG);
dprintf(fd, ")\n\n");
close(fd);
return 0;
}