So, I'm having a really weird issue... i'm trying simple file
encryption/decryption with BIO_*, but if the encrypted file is in a
subdirectory.. i get garbage data,
I'll post the code i'm using, with a brief elaboration on how i'm using it
and what behaviour i'm getting:
///////////////////////////////
/*
>
> Example of ssl read and write to a file
>
>
>> gcc ssl_write_read.c -lssl
>
> ./a.out
>
>
>>
>> */
>
>
>>
>>
>> #include <openssl/bio.h>
>
> #include <openssl/err.h>
>
> #include <openssl/rand.h>
>
> #include <openssl/ssl.h>
>
> #include <openssl/x509v3.h>
>
>
>> int read_whole_file( char* filename, char** data ){
>
> FILE* file = fopen( filename, "rb" );
>
> fseek( file, 0, SEEK_END );
>
> long fileSize = ftell( file );
>
> rewind( file );
>
> *data = malloc( fileSize );
>
> fread( *data, fileSize, 1, file );
>
> fclose( file );
>
> return fileSize;
>
> }
>
> void encrypt_file( char* filename ){
>
> char new_filename[strlen( filename + 4 )];
>
> strcpy( new_filename, filename );
>
> strcat( new_filename, ".enc" );
>
> char* data;
>
> int fileSize = read_whole_file( filename, &data );
>
> write_data( new_filename, data, fileSize, (unsigned char*)"mykey" );
>
> free( data );
>
> }
>
>
>> int write_data(const char *filename, char *out, int len, unsigned char
>> *key)
>
> {
>
> int total, written;
>
> BIO *cipher, *buffer, *file;
>
>
>
> /* Create a buffered file BIO for writing */
>
> file = BIO_new_file(filename, "wb");
>
> if (!file)
>
> return 0;
>
>
>
> /* Create a buffering filter BIO to buffer writes to the file */
>
> buffer = BIO_new(BIO_f_buffer( ));
>
>
>
> /* Create a base64 encoding filter BIO */
>
> // b64 = BIO_new(BIO_f_base64( ));
>
>
>
> /* Create the cipher filter BIO and set the key. The last parameter of
>
> BIO_set_cipher is 1 for encryption and 0 for decryption */
>
> cipher = BIO_new(BIO_f_cipher( ));
>
> BIO_set_cipher(cipher, EVP_des_ede3_cbc( ), key, NULL, 1);
>
>
>
> /* Assemble the BIO chain to be in the order cipher-b64-buffer-file */
>
> // BIO_push(cipher, b64);
>
> // BIO_push(b64, buffer);
>
> BIO_push(cipher,buffer);
>
> BIO_push(buffer, file);
>
>
>> /* This loop writes the data to the file. It checks for errors as if
>> the
>
> underlying file were non-blocking */
>
> for (total = 0; total < len; total += written)
>
> {
>
> if ((written = BIO_write(cipher, out + total, len - total)) <= 0)
>
> {
>
> if (BIO_should_retry(cipher))
>
> {
>
> written = 0;
>
> continue;
>
> }
>
> break;
>
> }
>
> }
>
>
>
> /* Ensure all of our data is pushed all the way to the file */
>
> BIO_flush(cipher);
>
>
>
> BIO_free_all(cipher);
>
> }
>
>
>> BIO* decrypt_open( const char *filename, unsigned char *key ){
>
> int total, written;
>
> BIO *cipher, *buffer, *file;
>
> //char *b = malloc(len);
>
>
>
> /* Create a buffered file BIO for reading */
>
> file = BIO_new_file(filename, "rb");
>
> if (!file)
>
> return 0;
>
>
>
> /* Create a buffering filter BIO to buffer writes to the file */
>
> buffer = BIO_new(BIO_f_buffer( ));
>
>
>
> /* Create a base64 encoding filter BIO */
>
> // b64 = BIO_new(BIO_f_base64( ));
>
>
>
> /* Create the cipher filter BIO and set the key. The last parameter of
>
> BIO_set_cipher is 1 for encryption and 0 for decryption */
>
> cipher = BIO_new(BIO_f_cipher( ));
>
> BIO_set_cipher(cipher, EVP_des_ede3_cbc( ), key, NULL, 0);
>
>
>
> /* Assemble the BIO chain to be in the order cipher-b64-buffer-file */
>
> // BIO_push(cipher, b64);
>
> // BIO_push(b64, buffer);
>
> BIO_push(cipher,buffer);
>
> BIO_push(buffer, file);
>
> return cipher;
>
> }
>
> char* decrypt_read( BIO* cipher, int len, char* b ){
>
> int total, written;
>
>
>> // char b[len + 1];
>
> for (total = 0; total < len; total += written)
>
> {
>
> if ((written = BIO_read(cipher, b, len - total)) <= 0)
>
> {
>
> if (BIO_should_retry(cipher))
>
> {
>
> written = 0;
>
> continue;
>
> }
>
> break;
>
> }
>
> }
>
>
>
> b[total] = '\0';
>
>
>
> return b;
>
> }
>
>
>> int main(void)
>
> {
>
> //chdir("subdirectory");
>
> char *file_="test.txt";
>
> char* data = "howdy\n";
>
> write_data( file_, data, strlen(data), "mykey");
>
>
>> BIO* cipher = decrypt_open( file_, (unsigned char*)"mykey" );
>
> char b[999999];
>
> decrypt_read( cipher, 999999, b );
>
> BIO_flush( cipher );
>
> BIO_free_all( cipher );
>
> printf(">%s\n",b);
>
>
>> //char* test="plain.txt";
>
> //encrypt_file(test);
>
>
>> }
>
>
///////////////////////////////////////////////////////////
1. So, first run creates and writes encrypted file "test.txt" and then
decrypts and prints out the contents, "howdy",
2. Now, comment out line 141 // write_data( ... re-run to verify "howdy",
works fine
3. make directory "temp", move "test.txt" into "temp" and change line 139
to reflect that: char *file_="temp/test.txt";.. re-run - I get no results ??
4. Even more weird: change line 139 back to just "test.txt", and replace
file_ on line 143 with "temp/test.txt" ... so it reads: BIO* cipher =
decrypt_open( "temp/test.txt", (unsigned char*)"mykey" ); // re-run... now
it works again all of a sudden. BUT - if you comment out line 139 // char
*file_="test.txt";.... then it doesn't work again? Even though *file_ isn't
being used???
