enforce device type of mmcblk, fail if /sys/block/<device>/device is not a readable directory

1 files changed, 14 insertions, 12 deletions

diff --git a/genkey.c b/genkey.c
index 8bb224a..fd17060 100644
--- a/genkey.c
+++ b/genkey.c
@@ -1,8 +1,12 @@
+#define _XOPEN_SOURCE 700
 #include <ctype.h>
+#include <fcntl.h>
 #include <stdio.h>
 #include <string.h>
 #include <stdbool.h>
 #include <stdlib.h>
+#include <unistd.h>
+
 #include "deonebook.h"
 
 #define SCR_SIZE 8
@@ -34,27 +38,25 @@ static unsigned char twiddle(unsigned char buf[2])
 	return c;
 }
 
-static bool get_sd_register(const char *dev, const char *reg, size_t n, unsigned char buf[n])
+static bool get_sd_register(int dirfd, const char *reg, size_t n, unsigned char buf[n])
 {
-	char path[256];
-	snprintf(path, sizeof(path), "/sys/block/%s/device/%s", dev, reg);
-
-	FILE *f = fopen(path, "r");
-	if (f == NULL) {
+	int fd = openat(dirfd, reg, O_RDONLY);
+	if (fd == -1) {
 		return false;
 	}
 
 	for (size_t i = 0; i < n; i++) {
 		unsigned char hex[2];
-		fread(hex, 2, 1, f);
+		read(fd, hex, sizeof(hex));
 		buf[i] = twiddle(hex);
 	}
 
-	fclose(f);
+	close(fd);
+
 	return true;
 }
 
-unsigned char * genkey(const char *dev)
+unsigned char * genkey(int dirfd)
 {
 	static unsigned char key[KEY_SIZE];
 	const unsigned char keycode[] = "eone";
@@ -65,15 +67,15 @@ unsigned char * genkey(const char *dev)
 	unsigned char csd[CSD_SIZE] = "testtesttesttest";
 	unsigned char cid[CID_SIZE] = "testtesttesttest";
 
-	if (!get_sd_register(dev, "cid", sizeof(cid), cid)) {
+	if (!get_sd_register(dirfd, "cid", sizeof(cid), cid)) {
 		fprintf(stderr, "warning: CID register not read\n");
 		allread = false;
 	}
-	if (!get_sd_register(dev, "csd", sizeof(csd), csd)) {
+	if (!get_sd_register(dirfd, "csd", sizeof(csd), csd)) {
 		fprintf(stderr, "warning: CSD register not read\n");
 		allread = false;
 	}
-	if (!get_sd_register(dev, "scr", sizeof(scr), scr)) {
+	if (!get_sd_register(dirfd, "scr", sizeof(scr), scr)) {
 		fprintf(stderr, "warning: SCR register not read\n");
 		allread = false;
 	}