[erlang-questions] crypto:md5/1 vs openssl md5

[Tony Rogvall]

Problem is newline!


Testing with string input:

Erlang-version:

[ lists:nth(X+1,"0123456789abcdef") || <<X:4>> <= crypto:md5("hello-world")].      
"2095312189753de6ad47dfe20cbe97ec"


Port with -n flag work!!

18> open_port({spawn,"echo -n hello-world | openssl md5"}, []).
#Port<0.1075>
19> flush().
Shell got {#Port<0.1075>,{data,"(stdin)= 2095312189753de6ad47dfe20cbe97ec\n"}}
ok

Without a -n flag you get a newline in input, does not match

20> open_port({spawn,"echo hello-world | openssl md5"}, []).   
#Port<0.1076>
21> flush().
Shell got {#Port<0.1076>,{data,"(stdin)= 8a8933dab8deebe52e30886da1ef6ee2\n"}}
ok

Same as above.

22> os:cmd("echo hello-world | openssl md5").                      
"(stdin)= 8a8933dab8deebe52e30886da1ef6ee2\n"

But this is truly strange :-)

24> os:cmd("echo -n hello-world | openssl md5").
"(stdin)= c298a9eb9b7697afa9b4b7bbd6b012b1\n"

Until you read os.erl and see that the command is mangled into the form:

os:cmd corresponds in doing the following commands:

40> Port = open_port({spawn, "/bin/sh -s unix:cmd 2>&1"}, [stream]).
41> erlang:port_command(Port, "(echo -n hello-world | openssl md5) < /dev/null; echo \"\^D\"\n").
true
42> flush().
Shell got {#Port<0.943>,{data,"(stdin)= c298a9eb9b7697afa9b4b7bbd6b012b1\n"}}
Shell got {#Port<0.943>,{data,[4,10]}}
ok

Testing a bit more yield:

64> Port = open_port({spawn, "/bin/sh -s unix:cmd 2>&1"}, [stream]).
65> erlang:port_command(Port, "(echo -n hello-world | cat) < /dev/null; echo \"\^D\"\n").
66> flush().
Shell got {#Port<0.1077>,{data,"-n hello-world\n"}}
Shell got {#Port<0.1077>,{data,[4,10]}}

so  -n is not accepted by /bin/sh version of echo!
verifying this:

[ lists:nth(X+1,"0123456789abcdef") || <<X:4>> <= crypto:md5("-n hello-world\n")].    
"c298a9eb9b7697afa9b4b7bbd6b012b1"

/Tony


On 10 feb 2012, at 06:26, CGS wrote:

> 
> Hi,
> 
> Just for my curiosity, does anybody know if crypto:md5/1 in R14B03 is intentionally different from openssl md5? (The sha matches perfectly.)
> 
> Just a short test (Erlang shell):
> 1> RB = crypto:rand_bytes(16).                                                 
> <<141,190,84,7,129,230,147,112,200,205,68,80,240,78,68,198>>                    
> 2> MD5 = crypto:md5(RB).                                                       
> <<97,59,0,195,229,254,195,237,238,126,156,14,33,142,206,183>>
> 3> lists:flatten(lists:map(fun([X,Y])->[case X>64 of true -> X+32; false-> X end,case Y>64 of true -> Y+32; false -> Y end];([X])->[$0,case X>64 of true -> X+32; false -> X end] end, lists:map(fun(X)->integer_to_list(X,16) end, binary_to_list(RB)))).                   
> "8dbe540781e69370c8cd4450f04e44c6"
> 4> lists:flatten(lists:map(fun([X,Y])->[case X>64 of true -> X+32; false-> X end,case Y>64 of true -> Y+32; false -> Y end];([X])->[$0,case X>64 of true -> X+32; false -> X end] end, lists:map(fun(X)->integer_to_list(X,16) end, binary_to_list(MD5)))).
> "613b00c3e5fec3edee7e9c0e218eceb7"
> 5> os:cmd("echo \"8dbe540781e69370c8cd4450f04e44c6\" | openssl md5").          
> "(stdin)= 6007d8f36b589078f3565b5c90cedffc\n"                                   
> 
> As you can see the same rand number, "8dbe540781e69370c8cd4450f04e44c6", gives in crypto:md5 "613b00c3e5fec3edee7e9c0e218eceb7" while in openssl md5 "6007d8f36b589078f3565b5c90cedffc". Please, let me know if I do something wrong.
> 
> CGS
> 
> _______________________________________________
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