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Is there a simple way to get a list of all fingerprints entered in the .ssh/authorized_keys || .ssh/authorized_keys2 file?

ssh-keygen -l -f .ssh/authorized_keys 

will only return fingerprint of first line / entry / publickey

hack with awk:

awk 'BEGIN { 
    while (getline < ".ssh/authorized_keys") {
        if ($1!~"ssh-(r|d)sa") {continue}
        print "Fingerprint for "$3
        system("echo " "\""$0"\"> /tmp/authorizedPublicKey.scan; \
            ssh-keygen -l -f /tmp/authorizedPublicKey.scan; \
            rm /tmp/authorizedPublicKey.scan"
        )
    }
}'

but is there an easier way or ssh command I didn't find?

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2 Answers 2

up vote 8 down vote accepted

Here's another hack using plain bash without temporary files:

while read l; do
  [[ -n $l && ${l###} = $l ]] && ssh-keygen -l -f /dev/stdin <<<$l;
done < .ssh/authorized_keys

You can easily make it a function in your .bashrc:

function fingerprints() {
  local file="$1"
  while read l; do
    [[ -n $l && ${l###} = $l ]] && ssh-keygen -l -f /dev/stdin <<<$l
  done < $file
}

and call it with:

$ fingerprints .ssh/authorized_keys
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1  
nice @Raphink , thank you. added code.childno.de/marcel/changeset/afdce0dd ;) One note: ssh-keygen -l -f /dev/stdin seems not to work on a mac.. nevertheless not relevant for servers but gnaa apple or is it a BSD "problem" getting /dev/stdin is not a public key file.?! –  childno.de Aug 1 '12 at 12:16
1  
Reading from /dev/stdin is not a great idea in general, it's better to use -, but for some reason ssh-keygen doesn't know about -... –  ℝaphink Aug 1 '12 at 12:34
    
Doesn't work on Mac? –  Will Jul 28 at 1:13

Here's a portable way to show all key fingerprints for a given file, tested on Mac and Linux:

#!/bin/bash

fingerprint_keys()
{
    if (( $# != 1 )); then
        echo "Usage: ${FUNCNAME} <authorized keys file>" >&2
        return 1
    fi

    local file="$1"
    if [ ! -r "$file" ]; then
        echo "${FUNCNAME}: File '${file}' does not exist or isn't readable." >&2
        return 1
    fi

    # Must be declared /before/ assignment, because of bash weirdness, in
    # order to get exit code in $?.
    local TMPFILE

    TEMPFILE=$(mktemp -q -t "$0.XXXXXXXXXX")
    if (( $? != 0 )); then
        echo "${FUNCNAME}: Can't create temporary file." >&2
        return 1
    fi

    while read line; do
        # Make sure lone isn't a comment or blank.
        if [[ -n "$line" ]] && [ "${line###}" == "$line" ]; then
            # Insert key into temporary file (ignoring noclobber).
            echo "$line" >| "$TEMPFILE"

            # Fingerprint time.
            ssh-keygen -l -f "$TEMPFILE"

            # OVerwrite the file ASAP (ignoring noclobber) to not leave keys
            # sitting in temp files.
            >| "$TEMPFILE"
        fi
    done < "$file"

    rm -f "$TEMPFILE"
    if (( $? != 0 )); then
        echo "${FUNCNAME}: Failed to remove temporary file." >&2
        return 1
    fi
}

Example Usage:

bash $ fingerprint_keys ~/.ssh/authorized_keys
2048 xx:xx:xx:xx:xx:xx:xx:xx:bb:xx:xx:xx:xx:xx:xx:xx  x@x.local (RSA)
bash $ 
share|improve this answer
    
sorry to say that but that's neither "simplier", nor "smaller" not even "smarter" and doesn't take another approach than listed above. just a script using more error handlers ;) –  childno.de Jul 29 at 5:40
    
Which makes it safer, right? You're welcome to make edits but why downvote? I didn't propose that it was any kind of better solution than yours... I feel a secure tempfile is better, and that more safety is needed for scripting purposes. Also, the version above is noclobber-safe. –  Will Aug 2 at 2:05

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