1 files changed, 57 insertions, 0 deletions
diff --git a/decrypt.c b/decrypt.c
new file mode 100644
index 0000000..b41ed9b
--- /dev/null
+++ b/decrypt.c
@@ -0,0 +1,57 @@
+#define _XOPEN_SOURCE 700
+#include <errno.h>
+#include <fcntl.h>
+#include <libgen.h>
+#include <stdio.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "deonebook.h"
+
+#define CBC 1
+#define ECB 0
+#define CTR 0
+#include "tiny-AES-c/aes.c"
+
+int decrypt(const unsigned char *key, const char *in, const char *out)
+{
+	int fd = open(in, O_RDONLY);
+	if (fd == -1) {
+		perror(in);
+		return 1;
+	}
+
+	struct stat st;
+	if (fstat(fd, &st) != 0) {
+		perror(in);
+		return 1;
+	}
+
+	unsigned char *buf = mmap(NULL, st.st_size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
+	if (buf == MAP_FAILED) {
+		perror(in);
+		return 1;
+	}
+
+	close(fd);
+
+	unsigned char iv[IV_SIZE];
+	memset(iv, '\03', sizeof(iv));
+
+	struct AES_ctx ctx = {0};
+	AES_init_ctx_iv(&ctx, key, iv);
+	AES_CBC_decrypt_buffer(&ctx, buf, st.st_size);
+
+	fd = open(out, O_WRONLY | O_CREAT, 0644);
+	if (fd == -1) {
+		perror(out);
+		return 1;
+	}
+
+	write(fd, buf, st.st_size);
+	close(fd);
+
+	return 0;
+}