RSA(8)
NAME
rsagen, rsafill, asn12rsa, rsa2pub, rsa2ssh, rsa2x509 − generate and format rsa keys
SYNOPSIS
rsagen [ -b nbits ] [ -t tag ]
rsafill [ file ]
asn12rsa [ -t tag ] [ file ]
rsa2pub [ file ]
rsa2ssh [ file ]
rsa2x509 [ -e expiretime ] certinfo [ file ]
DESCRIPTION
Plan 9 represents an RSA key as an attribute-value pair list prefixed with the string key; this is the generic key format used by factotum(4). 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 are in hexadecimal except size , which is decimal. An RSA 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.
Rsagen prints a randomly generated RSA private key whose n has exactly nbits (default 1024) significant bits. If tag is specified, it is printed between key and proto=rsa; typically, tag is a sequence of attribute-value comments describing the key.
Rsafill reads a private key, recomputes the !kp, !kq, and !c2 attributes if they are missing, and prints a full key.
Asn12rsa reads an RSA private key stored as ASN.1 encoded in the binary Distinguished Encoding Rules (DER) and prints a Plan 9 RSA key, inserting tag exactly as rsagen 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 “RSA PRIVATE KEY.” The command:
auth/pemdecode ’RSA PRIVATE KEY’ | auth/asn12rsa
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 RSA key.
Rsa2pub reads a Plan 9 RSA public or private key, removes the private attributes, and prints the resulting public key. Comment attributes are preserved.
Rsa2ssh reads a Plan 9 RSA public or private key and prints the public portion in the format used by SSH: three space-separated decimal numbers size, ek, and n. For compatibility with external SSH implementations, the public keys in /sys/lib/ssh/keyring and $home/lib/keyring are stored in this format.
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:
auth/rsa2x509 ’C=US OU=”Bell Labs file |
auth/pemencode CERTIFICATE
generates such a textual certificate. Applications that serve TLS-encrypted sessions (for example, httpd(8), pop3(8), and tlssrv(8)) expect certificates in ASN.1/DER/PEM format.
EXAMPLES
Generate a fresh key and use it to start a TLS-enabled web server:
auth/rsagen -t ’service=tls owner=∗’ >key
auth/rsa2x509 ’C=US CN=∗.cs.bell-labs.com’ key |
auth/pemencode CERTIFICATE >cert
cat key >/mnt/factotum/ctl
ip/httpd/httpd -c cert
Generate a fresh key and configure a remote Unix system to allow use of that key for logins:
auth/rsagen -t ’service=ssh’ >key
auth/rsa2ssh key | ssh unix ’cat >>.ssh/authorized_keys’
cat key >/mnt/factotum/ctl
ssh unix
SOURCE
/sys/src/cmd/auth
SEE ALSO
BUGS
There are too many key formats.
Plan 9 — July 11, 2003