2019-06-24 09:52


I have to decrypt a file in my Laravel backend with PHP's openssl_decrypt. The file is encrypted outside Laravel fro ma BASH script and openssl 1.1.

I looked at some explanations that would help me but found nothing that worked. My openssl versions are the same (1.1) for both PHP and the server. I tried many combinations of options but nothing worked.

Here is my BASH encrypting script:

# We're looking for ".decrypted" files, which gonna be encrypted next
FILES_LIST=$(find $FILES_PATH -type f -name '*.decrypted' )
# We base64-decode the key then display it as Hex. string
KEY=$(echo $APP_KEY | base64 -d -i | xxd -p -c 64)

# For each file to encrypt :
while read -r file; do
  # If there is actually a file :
  if [ ! -z "$file" ]; then
    # We have to split the files into 32M. chunks because our server can't decrypt big files without memory leaks in php.
    split -b 32M -d $file -a 3 $chunkspath
    chunkslist=$(find $FILES_PATH -type f -name $chunksname)
    touch $output
    # For each chunk :
    while read -r chunk; do
      # Generate a random IV of 16 bytes (output is 32 characters in Hex.)
      iv=$(openssl rand -hex 16)
      openssl AES-256-CBC -K $KEY -iv $iv -in $chunk -out $temp
      # We prefix each chunk with his IV to let the server retrieve it when decrypting. See the PHP code bellow.
      echo -n $iv >> $output
      # Then we append each IV+Chunk in the final output file.
      cat $temp >> $output
      rm $temp $chunk
    done < <(echo "${chunkslist}")
    # I commented the next line to let me run some tests but the original file will have to be removed eventually.
    # rm $file
done < <(echo "${FILES_LIST}")

echo 'Done'

And here's my PHP's script for decrypting the file:

// This function is inside a Laravel's stream download response 
    function () use ($file, $log) { // $file is the Laravel model representation of a stored file.
        $cipher = 'AES-256-CBC';
        $key = base64_decode(substr(config('app.key'), 7));
        $ivLen = 32; // Actually 16 bytes but 32 characters in hex format
        $chunckLen = 32 * 1024 * 1024; // Chunks are 32Mo long or less for the last one
        $fpIn = fopen(Storage::disk('files')->path($file->path), 'rb');
        while (!feof($fpIn)) {
            // IV and Key must be in binary format
            $iv = hex2bin(fread($fpIn, $ivLen));
            // We read the file chunks by chunks, decrypt it and print it.
            $encrypted = fread($fpIn, $chunckLen);
            $decrypted = openssl_decrypt($encrypted, $cipher, $key, OPENSSL_RAW_DATA, $iv);
            while ($msg = openssl_error_string()) {
                print $msg . "

I expect the decrypted file to be readable. With the code above, the output file contains this line: error:06065064:digital envelope routines:EVP_DecryptFinal_ex:bad decrypt I tried with the OPENSSL_ZERO_PADDING options on the openssl_decrypt() method. The output file then contains binary data but the file is not readable (I guess the ecryption did not work as expected). I also tried to set the -nopad option in the bash script but then this error is thrown: 4960:error:0607F08A:digital envelope routines:EVP_EncryptFinal_ex:data not multiple of block length:../openssl-1.1.1c/crypto/evp/evp_enc.c:425:. Does someone know what there errors mean ? What did I do wrong ? I'm almost sure I missed something (I'm kind of new in the encryption world...)

Thank you!

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  • drxvjnx58751 drxvjnx58751 2年前

    Actually I just realized that the Key used in the script and the one used in Laravel weren't the same... Stupid me. The code above is therefore correct and resolves my problem.

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