1 Topic by ravi.kumar (edited by ravi.kumar 2016-09-13 22:09:59)

  • Registered: 2016-09-10
  • Posts: 18

Topic: [SOLVED] Unable to load RSA private key

Hi all,

I am using cyassl-3.3.0 cypto library for our product. I had one certificate consisted of RSA private key, client certificate, one intermediate CA and root CA. Please check the attachment. When I am using example project given with cyassl-3.3.0 or our product, I am getting following error "yassl error: can't load server private key file, check file and run from CyaSSL home dir". I debugged further and found that private key loading is failing from the function GetInt() which is called by RsaPrivateKeyDecode() due to ASN_PARSE_E  (-140). I checked the private key through openssl utility of Linux 
"openssl rsa -in private_key.pem -text -noout" and found correct parsing with openssl version 1.0.1e-fips 11 Feb 2013.  I need help to resolve this issue. I downloaded the latest release wolfssl-3.9.8  from wolfssl site and got the same issue of loading private key failure.

See the out of "openssl rsa -in private_key.pem -text -noout" for the private_key.pem.

Private-Key: (2048 bit)
modulus:
    00:d0:17:98:a5:7d:41:9f:45:72:45:c0:d0:e6:9b:
    82:9e:02:74:c1:2f:d3:93:ea:83:6e:47:05:7d:88:
    23:4c:99:ba:75:88:3f:2b:71:0a:98:76:ad:d2:0f:
    82:b7:6a:07:01:72:03:12:f0:c5:be:29:78:f5:cf:
    d1:f7:ae:19:d8:03:12:4c:b4:02:31:f6:22:34:11:
    0e:10:37:39:4a:55:86:89:63:15:f4:5e:b2:3c:27:
    d2:0e:05:16:36:5e:e3:90:dc:4e:da:60:2a:5e:f3:
    aa:fe:76:d4:f7:f6:ab:ed:a3:13:6b:23:d3:b8:9d:
    cc:68:94:c3:60:cd:4f:73:9f:6b:4d:e3:71:08:8d:
    31:05:1e:c0:94:ac:18:f8:86:d1:29:df:55:91:ca:
    f3:4e:1d:9a:db:1b:79:15:76:1e:5f:af:98:d9:db:
    15:e5:d1:08:cc:9d:76:33:47:bb:f6:49:34:cc:3c:
    2f:30:79:84:4c:9f:fa:af:90:bc:30:c6:e4:e1:94:
    9d:e2:c6:8f:7e:57:54:1e:8a:86:c7:c1:0a:4e:de:
    34:98:13:97:f6:b6:de:a1:a1:1f:c8:71:6b:12:51:
    25:b4:fd:66:ca:9d:0e:0d:8a:13:6f:6b:a7:ee:f7:
    aa:b7:50:c7:a5:69:57:e4:ab:6b:94:ea:a7:05:59:
    13:d1
publicExponent: 65537 (0x10001)
privateExponent:
    64:52:bb:f9:2d:06:32:2f:5d:04:5c:0d:5a:e0:a6:
    7c:5f:5a:c2:b8:b8:1c:9b:f7:79:77:2c:22:75:3b:
    ef:76:3d:fa:e4:10:f0:74:b3:53:06:04:8f:3d:83:
    1b:c2:36:56:70:0d:23:58:89:3d:40:e9:5c:39:31:
    55:63:ce:79:e2:21:34:71:a4:8d:49:c8:fb:a9:2d:
    4a:8c:15:46:cd:2c:eb:97:a5:c2:06:d5:8f:42:f3:
    76:66:e5:6a:99:1c:c5:7e:31:55:fe:fe:ee:80:33:
    74:32:fe:41:fd:de:ad:d6:ed:49:be:20:18:e5:9a:
    e2:e0:b5:c1:39:ba:90:56:ef:da:bf:a7:cc:29:44:
    0e:8b:0b:e6:00:d8:81:73:8f:5f:ad:c8:0b:f4:10:
    6a:ec:aa:58:a5:9e:20:8d:9c:37:dd:de:9b:80:89:
    11:6c:63:d9:13:60:f8:4d:0d:40:ac:57:8f:7d:95:
    af:b7:ae:bd:01:61:82:27:34:7a:a9:27:e4:ae:42:
    0f:fc:ae:1f:39:d8:0b:a7:2f:64:f3:a8:3e:ea:b9:
    15:b1:b3:cf:18:a7:dd:78:cf:c8:1c:8f:07:4d:03:
    6e:3d:51:b7:72:56:48:1d:4e:df:b4:a9:5a:57:4b:
    8a:fb:11:eb:ea:e4:25:08:9c:98:6e:68:4f:7d:db:
    41
prime1:
    00:fe:87:76:33:44:5a:37:e1:ce:a3:d4:19:6e:60:
    cb:93:95:30:64:0d:83:f4:4a:b0:25:2b:bc:7c:fd:
    ee:97:dd:e7:81:a3:90:e1:df:87:b2:fc:4a:5b:d8:
    29:e8:fc:02:13:43:57:11:65:6d:85:f0:ec:1a:fa:
    67:0d:cc:c9:77:5a:a9:a7:67:5e:b1:0c:6c:fd:fb:
    e4:12:49:ac:56:be:eb:b3:d7:b9:c3:a9:a4:b6:b5:
    88:ca:23:59:6e:7b:a4:65:25:09:b0:03:b2:d9:9e:
    d8:c2:29:b0:1b:eb:e2:86:fb:4e:cb:fd:bc:4e:0c:
    8c:bb:51:76:eb:7f:83:9a:85
prime2:
    00:d1:4b:70:1a:e5:47:be:e6:74:ae:b6:f0:fd:37:
    ab:8c:3e:77:33:ae:a2:9d:25:59:e8:1c:75:e8:6f:
    32:c4:ea:40:78:7e:47:0e:0e:bb:c2:fd:05:eb:8f:
    47:64:7b:17:63:f1:46:8f:ab:1c:db:de:89:97:89:
    46:68:25:12:0d:41:c5:8a:58:cd:8d:42:c2:a4:21:
    d0:55:dd:5f:1a:68:7b:34:6c:a5:d9:59:b4:ec:56:
    43:12:74:06:01:ad:8e:2b:10:9c:3d:f3:0e:43:20:
    54:a2:ad:0e:89:c8:ad:0e:f9:5e:99:e2:7d:f2:8a:
    ea:45:0b:a6:cd:a8:12:a3:dd
exponent1:
    00:f2:e5:b7:09:29:bb:a7:04:98:bc:83:56:59:9d:
    89:e9:27:40:6c:da:f1:08:1a:96:8a:82:78:78:17:
    a4:af:cd:16:77:02:ee:ea:7e:f4:f2:fc:0c:c2:25:
    41:a9:93:85:2f:78:de:08:3d:f1:0d:17:63:5a:43:
    88:41:05:23:66:01:61:51:de:35:e1:63:e8:47:61:
    30:bf:bb:0a:fa:25:6c:ad:cd:ba:fb:5c:53:52:01:
    5f:ae:f7:99:0a:f4:77:68:06:b6:7e:00:a9:97:40:
    1d:be:fd:25:91:1f:c4:a7:e7:ff:c4:70:3a:59:89:
    64:6c:06:4c:24:65:25:e4:39
exponent2:
    78:b8:03:74:6f:f5:1f:06:3c:1d:1e:46:08:38:19:
    09:ae:6a:00:f4:64:b5:31:7b:17:27:7b:56:d2:f4:
    bc:a1:c5:07:fb:06:2e:f4:8e:96:5c:6d:12:be:b4:
    d6:1f:2d:91:a6:f4:25:1f:f4:68:59:86:91:52:4b:
    ba:fc:4e:da:38:aa:a1:2e:b1:79:1e:1d:b8:a0:0c:
    53:ca:78:f5:79:78:3e:f7:bf:fd:8b:01:91:23:fc:
    51:e3:7c:27:71:9c:c3:f8:33:b6:83:c0:21:35:bf:
    bb:89:08:0e:af:22:2a:b5:e9:3b:e7:68:f0:01:f2:
    38:5b:0d:1e:28:28:80:3d
coefficient:
    00:c4:95:c3:5e:63:fd:17:98:68:56:53:fd:f8:e3:
    99:28:40:f9:54:2d:03:52:e4:c9:2d:2c:93:65:bc:
    ec:94:5d:fd:bf:1b:b4:4a:4f:18:3b:56:e1:4d:6f:
    5c:20:81:64:df:74:7a:d6:e8:cb:cc:23:44:4d:00:
    76:3f:6c:29:ee:0c:5a:03:50:0c:34:13:4f:d8:03:
    a0:61:22:c4:dd:9f:6f:9f:b2:9b:38:e3:1c:9d:a2:
    f1:39:ea:33:bb:8c:52:fa:5e:6b:35:b4:83:a9:3f:
    4d:8e:e1:42:31:f7:10:52:43:45:b5:5a:22:b6:b7:
    07:fd:48:63:b2:61:84:d8:18

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  • From: Bozeman
  • Registered: 2014-05-09
  • Posts: 777

Re: [SOLVED] Unable to load RSA private key

Hi ravi.kumar,

The key is improperly formatted. I'm honestly surprised openssl is able to parse it. Just do this command and compare the outputs:

openssl rsa -inform pem -in private_key.pem -outform pem -out private_key_try2.pem

now diff the two files and you'll see they do not match in any way. If you do the same command on our existing ca-key.pem in the <wolfssl-root>/certs directory:

openssl rsa -inform pem -in ca-key.pem -outform pem -out ca-key_try2.pem

and diff those two files they remain identical in every way. Could you tell us where you got that RSA key you are using and how it was generated?


Fix for your issue is to use the resulting "private_key_try2.pem" from the command above. That is RFC compliant formatting and our libraries process it just fine.


Kind Regards,

Kaleb J. Himes's Website

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3 Reply by Kaleb J. Himes (edited by Kaleb J. Himes 2016-09-13 09:58:16)

  • From: Bozeman
  • Registered: 2014-05-09
  • Posts: 777

Re: [SOLVED] Unable to load RSA private key

Hi ravi.kumar,

Just as a followup I'll be discussing this with my colleagues and see if there is a fix we might introduce if the original format you sent is RFC compliant as well. We'll be doing some further investigation on this case for sure however testing multiple things and to fix the issue your currently facing it's easy enough to do as noted above and using the re-formatted "private_key_try2.pem".

openssl rsa -inform pem -in private_key.pem -outform pem -out private_key_try2.pem

I have verified the resulting "private_key_try2.pem" contains all the correct information, the modulus, privateExponent, prime1, prime2, exponent1, exponent2, and coefficient are all still the same, the only thing that changes is the hex representation of the key in the .pem file (the .pem format is the only thing that is modified).

We still look forward to hearing from you on how this key was generated / where it came from.

Kind Regards,

- Kaleb

Kaleb J. Himes's Website

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  • Registered: 2016-09-10
  • Posts: 18

Re: [SOLVED] Unable to load RSA private key

Hi Kaleb,

Thank you for your response. Finally I resolved the issue. Actually issue was with certificate. Whatever certificate we got from our customer is having private key in PKCS#8 format which has different ASN parsing code. If you see the input dump to RsaPrivateKeyDecode() function it is matching with the PKCS#8 ASN.1 parsing and it requires header and footer as "----BEGIN PRIVATE KEY---" and "---END PRIVATE KEY---" respectively. But customer is loading the private key as PKCS#1 format which has header and footer "---BEGIN RSA PRIVATE KEY---" and "---END RSA PRIVATE KEY----" respectively because of that Cyassl was throwing ASN parse error. If we  just change the header and footer of private key to the PKCS#8 format. it started working.

FYI:
1. PKCS#8 has following ASN.1 parsing (see the RFC 5208).
PrivateKeyInfo ::= SEQUENCE {
version Version,
privateKeyAlgorithm AlgorithmIdentifier PrivateKeyAlgorithms,
privateKey PrivateKey,
attributes [0] Attributes OPTIONAL }

Version ::= INTEGER
{v1(0)}

(v1,...)
PrivateKey ::= OCTET STRING

2. PKCS#1 has following ASN.1 parsing
RSAPrivateKey ::= SEQUENCE
{
  version Version,
  modulus INTEGER, -- n
  publicExponent INTEGER, -- e
  privateExponent INTEGER, -- d
  prime1 INTEGER, -- p
  prime2 INTEGER, -- q
  exponent1 INTEGER, -- d mod (p-1)
  exponent2 INTEGER, -- d mod (q-1)
  coefficient INTEGER, -- (inverse of q) mod p
  otherPrimeInfos OtherPrimeInfos OPTIONAL
}

Private key input was going as PKCS#8 format.
e.g.
0x30, 0x82, 0x4, 0xbe
0x2, 0x1, 0x0
0x30, 0xd, 0x6, 0x9, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0xd, 0x1, 0x1, 0x1, 0x5, 0x0 (failed at this point as PKCS#8 is expecting 0x2 INTEGER)
0x4, 0x82, 0x4, 0xa8, 0x30 ...

Thanks and Regards,
Ravi.

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