-
Notifications
You must be signed in to change notification settings - Fork 6
/
sshpubtorsa.py
69 lines (50 loc) · 2.18 KB
/
sshpubtorsa.py
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
#!/usr/bin/env python
# with help and inspiration from
# * ASN1_generate_nconf(3) (specifically the SubjectPublicKeyInfo structure)
# * http://www.sysmic.org/dotclear/index.php?post/2010/03/24/Convert-keys-betweens-GnuPG%2C-OpenSsh-and-OpenSSL
# * http://blog.oddbit.com/2011/05/converting-openssh-public-keys.html
import sys
import base64
import struct
from pyasn1.type import univ
from pyasn1.codec.der import encoder as der_encoder, decoder as der_decoder
if len(sys.argv) != 2:
sys.stderr.write("Usage: %s <public key file>\n" % sys.argv[0])
sys.exit(1)
keyfields = open(sys.argv[1]).read().split(None)
if len(keyfields) < 3:
# there might not be a comment, so pad it
keyfields.append("")
keytype, keydata, keycomment = keyfields
if keytype != 'ssh-rsa':
sys.stderr.write("%s: key type does not appear to be ssh-rsa\n")
sys.exit(1)
keydata = base64.b64decode(keydata)
parts = []
while keydata:
# read the length of the data
dlen = struct.unpack('>I', keydata[:4])[0]
# read in <length> bytes
data, keydata = keydata[4:dlen+4], keydata[4+dlen:]
parts.append(data)
e_val = eval('0x' + ''.join(['%02X' % struct.unpack('B', x)[0] for x in parts[1]]))
n_val = eval('0x' + ''.join(['%02X' % struct.unpack('B', x)[0] for x in parts[2]]))
bitstring = univ.Sequence()
bitstring.setComponentByPosition(0, univ.Integer(n_val))
bitstring.setComponentByPosition(1, univ.Integer(e_val))
bitstring = der_encoder.encode(bitstring)
bitstring = ''.join([('00000000'+bin(ord(x))[2:])[-8:] for x in list(bitstring)])
bitstring = univ.BitString("'%s'B" % bitstring)
pubkeyid = univ.Sequence()
pubkeyid.setComponentByPosition(0, univ.ObjectIdentifier('1.2.840.113549.1.1.1')) # == OID for rsaEncryption
pubkeyid.setComponentByPosition(1, univ.Null(''))
pubkey_seq = univ.Sequence()
pubkey_seq.setComponentByPosition(0, pubkeyid)
pubkey_seq.setComponentByPosition(1, bitstring)
print ("-----BEGIN PUBLIC KEY-----")
if keycomment:
print ("X-Comment: " + keycomment)
print
base64.MAXBINSIZE = (64//4)*3 # this actually doesn't matter, but it helped with comparing to openssl's output
print (base64.encodestring(der_encoder.encode(pubkey_seq)),)
print ('-----END PUBLIC KEY-----')