crypto/ssh ParsePublicKey "short read" error

Question

In a program I am developing I need a way to add public keys into the authorized_keys file during development, so I am using command line arguments to do so.

I have omitted most of the code, but if you would like to view all of the code, here is the repository, with the problem line being located in main.go on line 20.

b, err := ioutil.ReadFile(os.Args[1])
if err != nil {
    log.Fatalf("Fatal error trying to read new public key file: %s", err)
}

newAuthorizedKey, err := ssh.ParsePublicKey(b)
if err != nil {
    log.Fatalf("Fatal error trying to parse new public key: %s", err)
}

The "short read" error comes from the ssh.ParsePublicKey function. The command line argument that I am passing in is the location of a public key to add to the authorized_keys file of this program (e.g. ~/.ssh/id_rsa.pub). I have ensured that the file is correctly being passed into the program.

I have looked at the source code in hopes of debugging this "short read" error, but I can't figure out what is going on. The location for source code of the ParsePublicKey function in crypto/ssh is located here, and the location of source code of the parseString function, which is what the ParsePublicKey function is using to generate the "short read" error, is located here, also in crypto/ssh.

Answer 1

I think some of the comments to the question lead at this, but the function ssh.ParseAuthorizedKey([]byte) is able to read interpret the file at ~/.ssh/id_rsa.pub.

https://godoc.org/golang.org/x/crypto/ssh#ParseAuthorizedKey

Your example should work like this:

b, err := ioutil.ReadFile(os.Args[1])
if err != nil {
    log.Fatalf("Fatal error trying to read new public key file: %s", err)
}

newAuthorizedKey, _, _, _, err := ssh.ParseAuthorizedKey(b)
if err != nil {
    log.Fatalf("Fatal error trying to parse new public key: %s", err)
}