Sometimes I use this automagically from a script... Just toss in the -kfile
flag.
Decrypt:
#!/bin/bash
openssl enc -aes-256-cbc -d -kfile /path/to/passwd_in_file.txt -in $1 -out `echo $1 | sed s/.enc//`
Encrypt:
#!/bin/bash
openssl enc -aes-256-cbc -kfile /path/to/passwd_in_file.txt -in $1 -out $1.enc