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Using SHA1 as a message digest when generating aes256 cbc key

I need to make a laboratory for my computer security class, where I have to use gpg and OpenSSL to ensure communication security. I am confused by this step:

Use 'openssl enc' command line symmetric cipher routine to generate a 
256bit AES key in CBC mode. You should use SHA1 as a message digest 
function for generating the key. Save generated secret key, IV, and 
salt into file named aes.key. (Use –P opting to print out the key, 
salt and IV used then immediately exit, don’t do any encryption at 
this step.)

But I'm browsing the man pages for openssl enc , and I don't see any options for digests. I know there is an openssl dgst command, but it just calculates the input hash. Is there a flaw in this question? What does it mean "You must use SHA1 as a message digest function to generate a key"? Am I generating a key and then just SHA1 (key.aes)?

Any help with this would be appreciated.

Thank.

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1 answer

openssl enc, , -h:

-md            the next argument is the md to use to create a key
                 from a passphrase.  One of md2, md5, sha or sha1

, -md sha1 SHA1 - . :

openssl enc -aes-256-cbc -md sha1 -P

, , -md .

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