From d17413ffe8186f82977d0d1e98d5955b4d51b50d Mon Sep 17 00:00:00 2001
From: cbdev <cb@cbcdn.com>
Date: Sat, 24 Jun 2023 23:38:03 +0200
Subject: Implement YHY NTAG reading

---
 nfcommander.h |  1 +
 reader.c      |  8 ++++--
 reader_yhy.c  | 85 +++++++++++++++++++++++++++++++++++++++++++++++++----------
 3 files changed, 78 insertions(+), 16 deletions(-)

diff --git a/nfcommander.h b/nfcommander.h
index 00f0fb8..0c24236 100644
--- a/nfcommander.h
+++ b/nfcommander.h
@@ -5,6 +5,7 @@
 #ifndef NFCOMMANDER_VERSION
         #define NFCOMMANDER_VERSION "v0.1-dev"
 #endif
+#define MIN(a,b) (((a) < (b)) ? (a) : (b))
 
 typedef enum {
 	tag_unset, /*unknown tag type*/
diff --git a/reader.c b/reader.c
index 5f1316b..f90ea52 100644
--- a/reader.c
+++ b/reader.c
@@ -97,9 +97,12 @@ static void reader_print_tag(nfc_tag_info_t tag){
 		case tag_desfire: type = "DESF"; break;
 	}
 
-	printf("[%s:%lu", type, tag.bytes_available);
+	printf("[%s:%lu ", type, tag.bytes_available);
+	if(tag.static_length){
+		printf("D:%lu:%lu ", tag.static_length, tag.dynamic_length);
+	}
 	for(n = 0; n < tag.uid_length; n++){
-		printf(" %02X", tag.uid[n]);
+		printf("%02X", tag.uid[n]);
 	}
 	printf("]");
 }
@@ -145,6 +148,7 @@ static int reader_process(){
 					printf("Slot %2lu: ", n);
 					reader_print_tag(tags[n].info);
 					printf(" valid\n");
+					printf("%s\n", tags[n].info.static_data);
 					//TODO
 					return 0;
 				}
diff --git a/reader_yhy.c b/reader_yhy.c
index 92d5080..704a053 100644
--- a/reader_yhy.c
+++ b/reader_yhy.c
@@ -1,6 +1,7 @@
 #include <stdio.h>
 #include <unistd.h>
 #include <sys/timerfd.h>
+#include <string.h>
 
 #include "nfcommander.h"
 #include "config.h"
@@ -42,8 +43,8 @@ int handle(int fd){
 }
 
 uint8_t read_ntag(nfc_tag_info_t* tag){
-	uint8_t data[16];
-	size_t bytes;
+	uint8_t data[16] = "";
+	size_t bytes = 0, n = 0;
 
 	//read 16 bytes starting at block 2
 	//[0-3] UID, lock bytes
@@ -86,13 +87,64 @@ uint8_t read_ntag(nfc_tag_info_t* tag){
 		return FLAG_TAG_UNPROGRAMMED;
 	}
 
-	
-	return 0;
+	//sanity check length data
+	if(data[12] < 6 || !data[13]){
+		return FLAG_TAG_UNPROGRAMMED;
+	}
+
+	//read data
+	tag->static_length = data[13] * tag->granularity;
+	tag->static_data = calloc(tag->static_length, sizeof(uint8_t));
+	if(!tag->static_data){
+		printf("Failed to allocate memory\n");
+		return FLAG_TAG_LOCKED;
+	}
+
+	do{
+		//each read fetches 4 blocks, but due to a probable firmware bug we cant read blocks 0 or 10
+		//so we overwrite 2 bytes per pass and skip the read for 10.
+		uint8_t block = data[12] + n * 2;
+		if(block != 10){
+			bytes = yhy_sync_read(reader_fd, block,
+					tag->static_data + n * 2 * 4, 
+					tag->static_length - (n * 2 * 4));
+		}
+		if(bytes <= 0){
+			return FLAG_TAG_LOCKED;
+		}
+		n++;
+	} while(n <= data[13] / 2);
+
+	//read dynamic data if present
+	tag->dynamic_length = data[15] * tag->granularity;
+	if(tag->dynamic_length){
+		tag->dynamic_data = calloc(tag->dynamic_length, sizeof(uint8_t));
+		if(!tag->dynamic_data){
+			printf("Failed to allocate memory\n");
+			return FLAG_TAG_LOCKED;
+		}
+
+		do{
+			uint8_t block = data[14] + n * 2;
+			if(block != 10){
+				bytes = yhy_sync_read(reader_fd, block,
+						tag->dynamic_data + n * 2 * 4, 
+						tag->dynamic_length - (n * 2 * 4));
+			}
+			if(bytes <= 0){
+				return FLAG_TAG_LOCKED;
+			}
+			n++;
+		} while(n <= data[15] / 2);
+
+	}
+
+	return FLAG_TAG_DATA_VALID;
 }
 
 uint8_t read_mifare(nfc_tag_info_t* tag){
 	//TODO
-	return 0;
+	return FLAG_TAG_LOCKED;
 }
 
 int scan(){
@@ -137,15 +189,20 @@ int scan(){
 			}
 		}
 
-		if(reader_tag_present(0, &card) == TAG_READ_REQUESTED){
-			//read card data
-			if(card.type == tag_ntag){
-				flags = read_ntag(&card);
-			}
-			else if(card.type == tag_mifare1){
-				flags = read_mifare(&card);
-			}
-			reader_tag_present(flags, &card);
+		switch(reader_tag_present(0, &card)){
+			case TAG_READ_REQUESTED:
+				//read card data
+				if(card.type == tag_ntag){
+					flags = read_ntag(&card);
+				}
+				else if(card.type == tag_mifare1){
+					flags = read_mifare(&card);
+				}
+				reader_tag_present(flags, &card);
+				break;
+			case TAG_WRITE_REQUESTED:
+				//TODO write card data
+				break;
 		}
 
 		yhy_sync_hlta(reader_fd);
-- 
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