How to resolve the EVP DecryptFInal ex bad decrypt during file decryption

Question

I have the following query Could any one please suggest me a solution   I m working on encryption and decryption of file for first time   I have encrypted file through command prompt using the command   openssl enc -aes-256-cbc -in file txt -out file enc -k  key value  -iv  iv value    I have to decrypt it programmatically  So I have written the program for it  but it is throwing the following error     exe file enc file directory     error  06065064  digital envelope routines  EVP DecryptFInal ex  bad decrypt  evp enc c     The program below takes input as directory path and search for encrypted file   enc  and try to decrypt it read into buffer   Code    include  lt stdio h gt   include  lt string h gt   include  lt stdlib h gt   include  lt dirent h gt   include  lt sys stat h gt   include  lt sys types h gt   include  lt openssl evp h gt   include  lt openssl err h gt   include  lt openssl conf h gt   include  lt libxml globals h gt   void handleErrors char  msg                  ERR print errors fp stderr           printf   s   msg           abort              void freeMemory char  mem        if  NULL    mem                free mem           mem   NULL              Function to decrypt the XML files     int decryptXML unsigned char  indata  unsigned char  outdata  int fsize         int outlen1   0  outlen2   0       unsigned char iv      b63e541bc9ece19a1339df4f8720dcc3       unsigned char ckey      70bbc518c57acca2c2001694648c40ddaf19e3b4fe1376ad656de8887a0a5ec2         if  NULL    indata                printf   input data is empty n            return 0             if  0  gt   fsize                printf   file size is zero n            return 0             outdata    char    malloc  sizeof  char    fsize   2        EVP CIPHER CTX ctx       EVP CIPHER CTX init  amp ctx        if    EVP DecryptInit ex   amp ctx  EVP aes 256 cbc    NULL  ckey  iv                 EVP CIPHER CTX cleanup  amp ctx       handleErrors  DInit               if    EVP DecryptUpdate   amp ctx  outdata   amp outlen1  indata  fsize                 EVP CIPHER CTX cleanup  amp ctx           handleErrors  DUpdate               if    EVP DecryptFinal ex   amp ctx  outdata   outlen1   amp outlen2                  EVP CIPHER CTX cleanup  amp ctx           handleErrors  DFinal               EVP CIPHER CTX cleanup  amp ctx        return outlen1 outlen2      int isDirectory char  path        DIR  dir   NULL      FILE  fin   NULL   fout   NULL      int enc len   0  dec len   0  fsize   0  ksize   0      unsigned char  indata   NULL   outdata   NULL      char buff BUFFER SIZE   file path BUFFER SIZE   cur dir BUFFER SIZE        struct dirent  in dir      struct stat s       if  NULL     dir   opendir path                  printf   ERROR  Failed to open the directory  s n   path           perror  cannot open             exit 1              while  NULL     in dir   readdir dir                   if   strcmp  in dir- gt d name           strcmp in dir- gt d name                     continue           sprintf  buff    s  s   path  in dir- gt d name            if  -1    stat buff   amp s                         perror  stat                exit 1                      if  S ISDIR s st mode                          isDirectory buff                     else                       strcpy file path  buff                if  strstr file path    enc                                      File to be decrypted                     fout   fopen file path  rb                      fseek  fout  0L  SEEK END                   fsize   ftell fout                   fseek  fout  0L  SEEK SET                    indata    char  malloc fsize                    fread  indata  sizeof char   fsize  fout                    if  NULL    fout                                        perror  Cannot open enc file                          return 1                                      dec len   decryptXML  indata  outdata  fsize                   outdata dec len      0                   printf    s n   outdata                   fclose  fin                   fclose  fout                                         closedir dir       freeMemory outdata       freeMemory indata        return 1       int main int argc  char  argv          int result       if  argc    2                printf   Usage   lt executable gt  path of the files n            return -1             ERR load crypto strings        OpenSSL add all algorithms        OPENSSL config NULL           Checking for the directory existance         result   isDirectory argv 1         EVP cleanup        ERR free strings         if  0    result          return 1      else        return 0      Thank you

User · Answer

I experienced a similar error reply while using the openssl command line interface, while having the correct binary key (-K). The option "-nopad" resolved the issue:

Example generating the error:

echo -ne "\x32\xc8\xde\x5c\x68\x19\x7e\x53\xa5\x75\xe1\x76\x1d\x20\x16\xb2\x72\xd8\x40\x87\x25\xb3\x71\x21\x89\xf6\xca\x46\x9f\xd0\x0d\x08\x65\x49\x23\x30\x1f\xe0\x38\x48\x70\xdb\x3b\xa8\x56\xb5\x4a\xc6\x09\x9e\x6c\x31\xce\x60\xee\xa2\x58\x72\xf6\xb5\x74\xa8\x9d\x0c" | openssl aes-128-cbc -d -K 31323334353637383930313233343536 -iv 79169625096006022424242424242424 | od -t x1

Result:

bad decrypt
140181876450560:error:06065064:digital envelope 
routines:EVP_DecryptFinal_ex:bad decrypt:../crypto/evp/evp_enc.c:535:
0000000 2f 2f 07 02 54 0b 00 00 00 00 00 00 04 29 00 00
0000020 00 00 04 a9 ff 01 00 00 00 00 04 a9 ff 02 00 00
0000040 00 00 04 a9 ff 03 00 00 00 00 0d 79 0a 30 36 38

Example with correct result:

echo -ne "\x32\xc8\xde\x5c\x68\x19\x7e\x53\xa5\x75\xe1\x76\x1d\x20\x16\xb2\x72\xd8\x40\x87\x25\xb3\x71\x21\x89\xf6\xca\x46\x9f\xd0\x0d\x08\x65\x49\x23\x30\x1f\xe0\x38\x48\x70\xdb\x3b\xa8\x56\xb5\x4a\xc6\x09\x9e\x6c\x31\xce\x60\xee\xa2\x58\x72\xf6\xb5\x74\xa8\x9d\x0c" | openssl aes-128-cbc -d -K 31323334353637383930313233343536 -iv 79169625096006022424242424242424 -nopad | od -t x1

Result:

0000000 2f 2f 07 02 54 0b 00 00 00 00 00 00 04 29 00 00
0000020 00 00 04 a9 ff 01 00 00 00 00 04 a9 ff 02 00 00
0000040 00 00 04 a9 ff 03 00 00 00 00 0d 79 0a 30 36 38
0000060 30 30 30 34 31 33 31 2f 2f 2f 2f 2f 2f 2f 2f 2f
0000100

User · Answer

This message digital envelope routines  EVP DecryptFInal ex  bad decrypt can also occur when you encrypt and decrypt with an incompatible versions of openssl   The issue I was having was that I was encrypting on Windows which had version 1 1 0 and then decrypting on a generic Linux system which had 1 0 2g   It is not a very helpful error message     Working solution   A possible solution from  AndrewSavinykh that worked for many  see the comments       Default digest has changed between those versions from md5 to sha256  One can specify the default digest on the command line as -md sha256 or -md md5 respectively

User · Answer

This message can also occur when you specify the incorrect decryption password  yeah  lame  but not quite obvious to realize this from the error message  huh     I was using the command line to decrypt the recent DataBase backup for my auxiliary tool and suddenly faced this issue   Finally  after 10 mins of grief and plus reading through this question answers I have remembered that the password is different and everything worked just fine with the correct password

User · Answer

Errors   Bad encrypt   decrypt   gitencrypt smudge  FAILURE  openssl error decrypting file   There are various error strings that are thrown from openssl  depending on respective versions  and scenarios  Below is the checklist I use in case of openssl related issues    Ideally  openssl is able to encrypt decrypt using same key    salt   amp  enc algo only  Ensure that openssl versions  used to encrypt decrypt   are compatible  For eg  the hash used in openssl changed at version 1 1 0 from MD5 to SHA256  This produces a different key from the same password  Fix   add  -md md5  in 1 1 0 to decrypt data from lower versions  and  add  -md sha256 in lower versions to decrypt data from 1 1 0 Ensure that there is a single openssl version installed in your machine  In case there are multiple versions installed simultaneously  in my machine  these were installed  -  LibreSSL 2 6 5  and  openssl 1 1 1d    make the sure that only the desired one appears in your PATH variable

User · Answer

My case  the server was encrypting with padding disabled  But the client was trying to decrypt with the padding enabled   While using EVP CIPHER   by default the padding is enabled  To disable explicitly we need to do  EVP CIPHER CTX set padding context  0     So non matching padding options can be one reason

User · Answer

I think the Key and IV used for encryption using command line and decryption using your program are not same   Please note that when you use the  -k   different from  -K    the input given is considered as a password from which the key is derived  Generally in this case  there is no need for the  -iv  option as both key and password will be derived from the input given with  -k  option   It is not clear from your question  how you are ensuring that the Key and IV are same between encryption and decryption   In my suggestion  better use  -K  and  -iv  option to explicitly specify the Key and IV during encryption and use the same for decryption  If you need to use  -k   then use the  -p  option to print the key and iv used for encryption and use the same in your decryption program   More details can be obtained at https   www openssl org docs manmaster apps enc html

[c] How to resolve the "EVP_DecryptFInal_ex: bad decrypt" during file decryption

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