Home / server / Questions / 486598
Accepted
enedebe
Asked: 2013-03-12 02:41:59 +0800 CST

Which is the maximum number of keys in authorized_keys file?

  • 772

I'm developing a solution which inserts a big number of SSH-keys into the authorized keys files of my SSH-server. Does anyone know the limit of keys that you can insert into that file? Are we talking about a hundred, thousand or tens of thousands? Any idea? And how is the performance affected when you have a large number of keys?

I suppose it is preferable to divide keys between various users, but I would like to know the limits of one user.

ssh-keys

2 Answers

  1. Best Answer

    There is no limit to the number of entries in the file. From the source code

    auth2-pubkey.c 
/* return 1 if user allows given key */
static int
user_key_allowed2(struct passwd *pw, Key *key, char *file)
{ ...

while (read_keyfile_line(f, file, line, sizeof(line), &linenum) != -1) {
    char *cp, *key_options = NULL;

    As you can see this simply loops over the file until read_keyfile_line returns -1.

    • 12

  2. There is no limit, but finding the correct key will be slow, like GREPing a large text file.

    • 2