RSA(1)

NAME
dsagen, rsagen, rsafill, asn12dsa, asn12rsa, dsa2pub, rsa2csr, rsa2pub, dsa2ssh, rsa2ssh, rsa2x509 - generate and format dsa and rsa keys

SYNOPSIS

dsagen [ -t tag ]

rsagen [ -b nbits ] [ -t tag ]

rsafill [ file ]

asn12dsa [ -t tag ] [ file ]

asn12rsa [ -t tag ] [ file ]

dsa2pub [ file ]

rsa2pub [ file ]

dsa2ssh [ file ]

rsa2ssh [ -2 ] [ file ]

rsa2x509 [ -e expiretime ] certinfo [ file ]

rsa2csr certinfo [ file ]

DESCRIPTION
Plan 9 represents DSA and RSA keys as attribute-value pair lists prefixed with the string key; this is the generic key format used by factotum((4)). A full DSA private key has the following attributes:

proto
    must be dsa

p   prime public modulus

q   prime group order; divides p-1

alpha
    group generator

key alpha^!secret mod p

!secret
    the secret exponent

A full RSA private key has the following attributes:

proto
    must be rsa

size
    the number of significant bits in n

ek  the encryption exponent

n   the product of !p and !q

!dk the decryption exponent

!p  a large prime

!q  another large prime

!kp, !kq, !c2
    parameters derived from the other attributes, cached to speed decryption

All the numbers in both keys are in hexadecimal except RSA's size , which is decimal. A public key omits the attributes beginning with A key may have other attributes as well (for example, a service attribute identifying how this key is typically used), but to these utilities such attributes are merely comments.

For example, a very small (and thus insecure) private key and corresponding public key might be:

        key proto=rsa size=8 ek=7 n=8F !dk=67 !p=B !q=D !kp=3 !kq=7 !c2=6
        key proto=rsa size=8 ek=7 n=8F

Note that the order of the attributes does not matter.

Dsagen prints a randomly generated DSA private key using the NIST-recommended algorithm. If tag is specified, it is printed between key and proto=dsa; typically, tag is a sequence of attribute-value comments describing the key.

Rsagen prints a randomly generated RSA private key whose n has exactly nbits (default 1024) significant bits.

Rsafill reads a private key, recomputes the !kp, !kq, and !c2 attributes if they are missing, and prints a full key.

Asn12dsa reads an DSA private key stored as ASN.1 encoded in the binary Distinguished Encoding Rules (DER) and prints a Plan 9 DSA key, inserting tag exactly as dsagen does. ASN.1/DER is a popular key format on Unix and Windows; it is often encoded in text form using the Privacy Enhanced Mail (PEM) format in a section labeled as an ``DSA PRIVATE KEY.'' The command:

        pemdecode 'DSA PRIVATE KEY' | asn12dsa

extracts the key section from a textual ASN.1/DER/PEM key into binary ASN.1/DER format and then converts it to a Plan 9 DSA key.

Asn12rsa is similar but operates on RSA keys.

Dsa2pub reads a Plan 9 DSA public or private key, removes the private attributes, and prints the resulting public key. Comment attribtes are preserved.

Rsa2pub is similar but operates on RSA keys.

Dsa2ssh reads a Plan 9 DSA public or private key and prints the public portion in the format used by SSH version 2 (version 1 did not support DSA). If the key has a comment attribute, that comment is appended to the key.

Rsa2ssh is similar but operates on RSA keys. It decides whether to print in version 1 or version 2 format by inspecting the service attribute.

Dsa2ssh and rsa2ssh are useful for generating SSH's authorized_keys file.

Rsa2x509 reads a Plan 9 RSA private key and writes a self-signed X.509 certificate encoded in ASN.1/DER format to standard output. (Note that ASN.1/DER X.509 certificates are different from ASN.1/DER private keys). The certificate uses the current time as its start time and expires expiretime seconds (default 3 years) later. It contains the public half of the key and includes certinfo as the issuer/subject string (also known as a ``Distinguished Name''). This info is typically in the form:

        C=US ST=NJ L=07974 O=Lucent OU='Bell Labs' CN=G.R.Emlin

The X.509 ASN.1/DER format is often encoded in text using a PEM section labeled as a ``CERTIFICATE.'' The command:

        rsa2x509 'C=US OU=''Bell Labs''' file |
        pemencode CERTIFICATE

generates such a textual certificate. Applications that serve TLS-encrypted sessions typically expect certificates in ASN.1/DER/PEM format.

Rsa2csr is like rsa2x509 but writes an X.509 certificate request.

EXAMPLES
Generate a fresh key and use it to start the Plan 9 TLS-enabled web server:

        rsagen -t 'service=tls owner=*' >key
        rsa2x509 'C=US CN=*.cs.bell-labs.com' key |
        	pemencode CERTIFICATE >cert
        cat key >/mnt/factotum/ctl
        ip/httpd/httpd -c cert

Generate a fresh set of SSH keys (only one is necessary), load them into factotum, and configure a remote Unix system to allow those keys for logins:

        rsagen -t 'service=ssh role=decrypt' >rsa1
        rsagen -t 'service=ssh-rsa role=sign' >rsa2
        dsagen -t 'service=ssh-dss role=sign' >dsa2

Convert existing Unix SSH version 2 keys instead of generating new ones:

        cd $HOME/.ssh
        pemdecode 'DSA PRIVATE KEY' id_dsa | asn12dsa >dsa2
        pemdecode 'RSA PRIVATE KEY' id_rsa | asn12rsa >rsa2

Load those keys into factotum:

        cat rsa1 rsa2 dsa2 | 9p write -l factotum/ctl
    Allow use of those keys for logins on other systems:

        rsa2ssh rsa1 >auth.keys
        rsa2ssh rsa2 >>auth.keys
        dsa2ssh dsa2 >>auth.keys
        scp auth.keys unix:.ssh/authorized_keys

SOURCE
/src/cmd/auth

SEE ALSO
factotum((4)), pem((1)), ssh((1))

BUGS
There are too many key formats.

There is no program to convert SSH version 1 RSA private keys.