CODEWITHSUNDEEP
opensslaes
joel
joel

Reputation: 7867

OpenSSL command line input data length

With the OpenSSL CLI, I am getting an error with a 16-byte input string

echo -e "abcdefgh\x08\x08\x08\x08\x08\x08\x08\x08" | openssl enc -aes-256-cbc -nopad -a -K 6162636465666768696A6B6C6D6E6F707172737475767778797A303132333435 -iv 61636567696B6D6F7173757779303234

stating

bad decrypt 140550741059328:error:0607F08A:digital envelope routines:EVP_EncryptFinal_ex:data not multiple of block length:crypto/evp/evp_enc.c:437

but if I alter the input string length to 15 bytes, abcdefgh\x08\x08\x08\x08\x08\x08\x08, the error does not occur. It occurs for 13, 14, 16 and 17-byte input. Not tried other lengths.

Given AES 256 CBC has a block length of 16 bytes, I don't see what I'm doing wrong.

Upvotes: 0

Views: 677

Answers (1)

oliv
oliv

Reputation: 13239

The echo adds a carriage return after the string, making the data to encrypt 17 bytes instead of 16.

So the openssl error is correct: data not multiple of block length

You should use the -n option of echo:

echo -ne "abcdefgh\x08\x08\x08\x08\x08\x08\x08\x08" | openssl enc -aes-256-cbc -nopad -K 6162636465666768696A6B6C6D6E6F707172737475767778797A303132333435 -iv 61636567696B6D6F7173757779303234

Upvotes: 1

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