calculate and check hash of downloaded file

CMakeLists.txt

@@ -12,7 +12,7 @@ set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -Wl,--no-as-needed")
 
 add_library(mfapi SHARED mfapi/mfconn.c mfapi/file.c mfapi/folder.c mfapi/apicalls/file_get_info.c mfapi/apicalls/user_get_info.c mfapi/apicalls/file_get_links.c mfapi/apicalls/user_session.c mfapi/apicalls/folder_get_info.c mfapi/apicalls/folder_create.c mfapi/apicalls/folder_get_content.c mfapi/apicalls/folder_delete.c mfapi/apicalls/device_get_status.c mfapi/apicalls/device_get_changes.c)
 
-add_library(mfutils SHARED utils/http.c utils/json.c utils/strings.c utils/stringv.c utils/xdelta3.c)
+add_library(mfutils SHARED utils/http.c utils/json.c utils/strings.c utils/stringv.c utils/xdelta3.c utils/hash.c)
 
 add_executable(mediafire-shell mfshell/main.c mfshell/mfshell.c mfshell/commands/folder.c mfshell/commands/auth.c mfshell/commands/chdir.c mfshell/commands/debug.c mfshell/commands/file.c mfshell/commands/get.c mfshell/commands/help.c mfshell/commands/host.c mfshell/commands/lcd.c mfshell/commands/links.c mfshell/commands/list.c mfshell/commands/lpwd.c mfshell/commands/mkdir.c mfshell/commands/pwd.c mfshell/commands/whoami.c mfshell/commands/rmdir.c mfshell/commands/status.c mfshell/commands/changes.c mfshell/config.c mfshell/options.c)
 target_link_libraries(mediafire-shell curl ssl crypto jansson mfapi mfutils)

fuse/hashtbl.c

@@ -33,6 +33,7 @@
 #include <pwd.h>
 #include <inttypes.h>
 #include <bits/fcntl-linux.h>
+#include <openssl/sha.h>
 
 #include "hashtbl.h"
 #include "../mfapi/mfconn.h"
@@ -41,6 +42,7 @@
 #include "../mfapi/apicalls.h"
 #include "../utils/strings.h"
 #include "../utils/http.h"
+#include "../utils/hash.h"
 
 /*
  * we build a hashtable using the first three characters of the file or folder
@@ -50,7 +52,9 @@
 #define NUM_BUCKETS 46656
 
 /*
- * we use this table to convert from a base36 char to an integer
+ * we use this table to convert from a base36 char (ignoring case) to an
+ * integer or from a hex string to binary (in the latter case letters g-z and
+ * G-Z remain unused)
  * we "waste" these 128 bytes of memory so that we don't need branching
  * instructions when decoding
  * we only need 128 bytes because the input is a *signed* char
@@ -60,12 +64,41 @@ static unsigned char base36_decoding_table[] = {
 /* 0x10 */ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
 /* 0x20 */ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
 /* 0x30 */ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 0, 0, 0, 0, 0,
-/* 0x40 */ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+/* 0x40 */ 0, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
-/* 0x50 */ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+/* 0x50 */ 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 0, 0, 0, 0, 0,
 /* 0x60 */ 0, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
 /* 0x70 */ 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 0, 0, 0, 0, 0
 };
 
+/*
+ * table to convert from a byte into the two hexadecimal digits representing
+ * it
+ */
+static char     base16_encoding_table[][2] = {
+    "00", "01", "02", "03", "04", "05", "06", "07", "08", "09", "0A", "0B",
+    "0C", "0D", "0E", "0F", "10", "11", "12", "13", "14", "15", "16", "17",
+    "18", "19", "1A", "1B", "1C", "1D", "1E", "1F", "20", "21", "22", "23",
+    "24", "25", "26", "27", "28", "29", "2A", "2B", "2C", "2D", "2E", "2F",
+    "30", "31", "32", "33", "34", "35", "36", "37", "38", "39", "3A", "3B",
+    "3C", "3D", "3E", "3F", "40", "41", "42", "43", "44", "45", "46", "47",
+    "48", "49", "4A", "4B", "4C", "4D", "4E", "4F", "50", "51", "52", "53",
+    "54", "55", "56", "57", "58", "59", "5A", "5B", "5C", "5D", "5E", "5F",
+    "60", "61", "62", "63", "64", "65", "66", "67", "68", "69", "6A", "6B",
+    "6C", "6D", "6E", "6F", "70", "71", "72", "73", "74", "75", "76", "77",
+    "78", "79", "7A", "7B", "7C", "7D", "7E", "7F", "80", "81", "82", "83",
+    "84", "85", "86", "87", "88", "89", "8A", "8B", "8C", "8D", "8E", "8F",
+    "90", "91", "92", "93", "94", "95", "96", "97", "98", "99", "9A", "9B",
+    "9C", "9D", "9E", "9F", "A0", "A1", "A2", "A3", "A4", "A5", "A6", "A7",
+    "A8", "A9", "AA", "AB", "AC", "AD", "AE", "AF", "B0", "B1", "B2", "B3",
+    "B4", "B5", "B6", "B7", "B8", "B9", "BA", "BB", "BC", "BD", "BE", "BF",
+    "C0", "C1", "C2", "C3", "C4", "C5", "C6", "C7", "C8", "C9", "CA", "CB",
+    "CC", "CD", "CE", "CF", "D0", "D1", "D2", "D3", "D4", "D5", "D6", "D7",
+    "D8", "D9", "DA", "DB", "DC", "DD", "DE", "DF", "E0", "E1", "E2", "E3",
+    "E4", "E5", "E6", "E7", "E8", "E9", "EA", "EB", "EC", "ED", "EE", "EF",
+    "F0", "F1", "F2", "F3", "F4", "F5", "F6", "F7", "F8", "F9", "FA", "FB",
+    "FC", "FD", "FE", "FF"
+};
+
 /*
  * a macro to convert a char* of the key into a hash of its first three
  * characters, treating those first three characters as if they represented a
@@ -79,6 +112,47 @@ static unsigned char base36_decoding_table[] = {
     base36_decoding_table[(int)(key)[1]]*36+\
     base36_decoding_table[(int)(key)[2]]
 
+/* decodes a zero terminated string containing hex characters into their
+ * binary representation. The length of the string must be even as pairs of
+ * characters are converted to one output byte. The output buffer must be at
+ * least half the length of the input string.
+ */
+static void hex2binary(const char *hex, unsigned char *binary)
+{
+    unsigned char   val1,
+                    val2;
+    const char     *c1,
+                   *c2;
+    unsigned char  *b;
+
+    for (b = binary, c1 = hex, c2 = hex + 1;
+         *c1 != '\0' && *c2 != '\0'; b++, c1 += 2, c2 += 2) {
+        val1 = base36_decoding_table[(int)(*c1)];
+        val2 = base36_decoding_table[(int)(*c2)];
+        *b = (val1 << 4) | val2;
+    }
+}
+
+static char    *binary2hex(unsigned char *binary, size_t length)
+{
+    char           *out;
+    char           *p;
+    size_t          i;
+
+    out = malloc(length * 2 + 1);
+    if (out == NULL) {
+        fprintf(stderr, "cannot allocate memory\n");
+        return NULL;
+    }
+    for (i = 0; i < length; i++) {
+        p = base16_encoding_table[binary[i]];
+        out[i * 2] = p[0];
+        out[i * 2 + 1] = p[1];
+    }
+    out[length * 2] = '\0';
+    return out;
+}
+
 struct h_entry {
     /*
      * keys are either 13 (folders) or 15 (files) long since the structure
@@ -124,7 +198,7 @@ struct h_entry {
      * only for files *
      ******************/
     /* SHA256 is 256 bits = 32 bytes */
-    unsigned char   hash[32];
+    unsigned char   hash[SHA256_DIGEST_LENGTH];
     /*
      * last access time to remove old locally cached files
      * atime is also never zero for files
@@ -751,6 +825,9 @@ int folder_tree_open_file(folder_tree * tree, mfconn * conn, const char *path)
     mffile         *file;
     int             retval;
     mfhttp         *http;
+    FILE           *fh;
+    unsigned char   hash[SHA256_DIGEST_LENGTH];
+    char           *hexhash;
 
     entry = folder_tree_lookup_path(tree, conn, path);
 
@@ -827,6 +904,39 @@ int folder_tree_open_file(folder_tree * tree, mfconn * conn, const char *path)
         return -1;
     }
 
+    /* size matches - now compare the hash as well */
+    fh = fopen(cachefile, "r");
+    if (fh == NULL) {
+        perror("cannot open file");
+        free(cachefile);
+        file_free(file);
+        return -1;
+    }
+
+    retval = calc_sha256(fh, hash);
+    if (retval != 0) {
+        fprintf(stderr, "failed to calculate hash\n");
+        free(cachefile);
+        file_free(file);
+        fclose(fh);
+        return -1;
+    }
+
+    fclose(fh);
+
+    if (memcmp(entry->hash, hash, SHA256_DIGEST_LENGTH) != 0) {
+        fprintf(stderr, "hashes are not equal\n");
+        hexhash = binary2hex(entry->hash, SHA256_DIGEST_LENGTH);
+        fprintf(stderr, "remote:     %s\n", hexhash);
+        free(hexhash);
+        hexhash = binary2hex(hash, SHA256_DIGEST_LENGTH);
+        fprintf(stderr, "downloaded: %s\n", hexhash);
+        free(hexhash);
+        free(cachefile);
+        file_free(file);
+        return -1;
+    }
+
     file_free(file);
 
     fd = open(cachefile, O_RDWR);
@@ -1030,6 +1140,9 @@ static struct h_entry *folder_tree_add_file(folder_tree * tree, mffile * file,
     new_entry->fsize = file_get_size(file);
     new_entry->needs_update = false;
 
+    /* convert the hex string into its binary representation */
+    hex2binary(file_get_hash(file), new_entry->hash);
+
     /* mark this h_entry struct as a file if its atime is not set yet */
     if (new_entry->atime == 0)
         new_entry->atime = 1;

mfapi/apicalls/folder_get_content.c

@@ -267,7 +267,7 @@ static int _decode_folder_get_content_files(mfhttp * conn, void *user_ptr)
                     file_set_revision(tmp_file,
                                       atoll(json_string_value(j_obj)));
                 }
-                // FIXME don't save hex ascii string but binary chars instead
+
                 j_obj = json_object_get(data, "hash");
                 if (j_obj != NULL) {
                     file_set_hash(tmp_file, json_string_value(j_obj));

mfapi/file.c

@@ -23,6 +23,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <openssl/sha.h>
 
 #include "file.h"
 #include "apicalls.h"
@@ -30,7 +31,9 @@
 struct mffile {
     char            quickkey[MFAPI_MAX_LEN_KEY + 1];
     char            parent[MFAPI_MAX_LEN_NAME + 1];
-    char            hash[65];
+    /* the hex representation takes twice the amount of the binary length plus
+     * 1 for the terminating zero byte */
+    char            hash[SHA256_DIGEST_LENGTH * 2 + 1];
     char            name[MFAPI_MAX_LEN_NAME + 1];
     time_t          created;
     uint64_t        revision;

utils/hash.c

@@ -0,0 +1,62 @@
+/*
+ * Copyright (C) 2014 Johannes Schauer <j.schauer@email.de>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2, as published by
+ * the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program; if not, write to the Free Software Foundation, Inc., 51
+ * Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ *
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <openssl/sha.h>
+#include <openssl/md5.h>
+
+#define bufsize 32768
+
+int calc_md5(FILE * file, unsigned char *hash)
+{
+    int             bytesRead;
+    char           *buffer;
+    MD5_CTX         md5;
+
+    MD5_Init(&md5);
+    buffer = malloc(bufsize);
+    if (buffer == NULL) {
+        return -1;
+    }
+    while ((bytesRead = fread(buffer, 1, bufsize, file))) {
+        MD5_Update(&md5, buffer, bytesRead);
+    }
+    MD5_Final(hash, &md5);
+    free(buffer);
+    return 0;
+}
+
+int calc_sha256(FILE * file, unsigned char *hash)
+{
+    int             bytesRead;
+    char           *buffer;
+    SHA256_CTX      sha256;
+
+    SHA256_Init(&sha256);
+    buffer = malloc(bufsize);
+    if (buffer == NULL) {
+        return -1;
+    }
+    while ((bytesRead = fread(buffer, 1, bufsize, file))) {
+        SHA256_Update(&sha256, buffer, bytesRead);
+    }
+    SHA256_Final(hash, &sha256);
+    free(buffer);
+    return 0;
+}

utils/hash.h

@@ -0,0 +1,25 @@
+/*
+ * Copyright (C) 2014 Johannes Schauer <j.schauer@email.de>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2, as published by
+ * the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program; if not, write to the Free Software Foundation, Inc., 51
+ * Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ *
+ */
+
+#ifndef _MFSHELL_HASH_H_
+#define _MFSHELL_HASH_H_
+
+int             calc_md5(FILE * file, unsigned char *hash);
+int             calc_sha256(FILE * file, unsigned char *hash);
+
+#endif