I am using mitmproxy on two different machines. The versions are
Mitmproxy: 4.0.4
Python: 3.8.2
OpenSSL: OpenSSL 1.1.1f 31 Mar 2020
Platform: Linux-5.4.0-33-generic-x86_64-with-glibc2.29
and
Mitmproxy: 5.1.1
Python: 3.8.2
OpenSSL: OpenSSL 1.1.1g 21 Apr 2020
Platform: macOS-10.15.4-x86_64-i386-64bit
One thing, that really puzzles me: How come that the ca-certificates have the same hash value? AFAIK, the key-pair of which the public one will go into the cert are created dynamically on installation or whenever someones deletes them in .mitmproxy. But interestingly, both have the same hash value:
> openssl x509 -in .mitmproxy/mitmproxy-ca-cert.pem -noout -hash
8bbe0e8d
This applies actually to a few more installations i did in order to investigate this behaviour. when I have a look at the modulus, all look different, so this seems to indicate that the keys are in fact different. But AFAIK the hash key is calculated over the key/modulus as well so I would like to know, why I find the same hash value 8bbe0e8d everywhere?
This leads to some interesting side effect: E.g. on linux the root ca certs are usually in /etc/ssl/certs. They are deployed there with a sensible name and in addition there is a a symlink pointing to that file. The name of the symlink ist the hash-value of the cert followed by a sequence number. This is generated by the c_rehash tool of openssl. Normally there are no hash collisions and all sequence numbers are 0.
But in the case of a linux system containing ca-certs of two different mitmproxy-instances we have something like this
# ls -l /etc/ssl/certs/ | grep mitm
lrwxrwxrwx 1 root root 21 Jun 1 21:45 8bbe0e8d.0 -> mitmproxy-systema-ca-cert.pem
-rw-r--r-- 1 root root 1318 Jun 1 21:44 mitmproxy-systema-ca-cert.pem
lrwxrwxrwx 1 root root 21 Jun 1 22:34 8bbe0e8d.1 -> mitmproxy-systemb-ca-cert.pem
-rw-r--r-- 1 root root 1318 Jun 1 22:34 mitmproxy-systemb-ca-cert.pem
So to repeat my question: Why is the hash value always 8bbe0e8d?
Thanks in advance
Please find the relevant openssl output below:
>> openssl x509 -in mitmproxy-systema-ca-cert.pem -text
Certificate:
Data:
Version: 3 (0x2)
Serial Number: 15904961119818 (0xe77298ec64a)
Signature Algorithm: sha256WithRSAEncryption
Issuer: CN=mitmproxy, O=mitmproxy
Validity
Not Before: May 24 12:28:31 2020 GMT
Not After : May 26 12:28:31 2023 GMT
Subject: CN=mitmproxy, O=mitmproxy
Subject Public Key Info:
Public Key Algorithm: rsaEncryption
Public-Key: (2048 bit)
Modulus:
00:d3:60:2a:3a:8b:bc:9a:2c:fb:da:90:33:fa:a1:
a9:7a:96:52:e4:73:56:c8:c8:7f:8b:f8:ab:4b:e0:
55:2e:05:75:5b:55:4d:6d:58:b0:82:56:23:ac:ee:
ba:d4:4e:b0:ab:8e:52:25:2c:12:ef:fe:23:3b:f5:
0d:26:9e:cd:1e:d5:7c:5a:7b:e0:c6:6b:af:b6:b0:
cd:d1:5b:8b:12:ea:a1:d4:15:78:37:84:f2:d1:48:
61:7b:9b:c6:ec:e3:2c:41:32:72:15:15:d1:5f:7b:
87:01:40:86:6a:cf:5f:2a:0f:19:71:c5:37:08:94:
8c:4d:18:af:5d:5d:80:89:46:e9:04:23:f4:e7:84:
4e:97:ee:81:91:07:c8:18:5e:eb:64:3a:47:9e:c1:
29:50:2c:27:c7:80:35:b9:d6:ec:61:91:de:23:af:
04:7d:0c:e8:43:32:52:09:c9:34:ba:fd:98:51:ef:
78:13:2c:83:4a:e9:31:6e:d8:53:6b:12:79:44:e9:
5b:70:7a:b5:79:2e:00:a9:9f:53:f3:2f:c6:75:b0:
90:1b:00:b4:50:21:5e:fe:b5:a3:36:18:c5:42:cd:
fc:d5:33:e4:1b:c1:26:12:04:05:95:e5:99:7c:23:
2a:ea:de:f3:45:7e:3b:9d:e9:56:a5:83:07:61:e9:
dd:19
Exponent: 65537 (0x10001)
X509v3 extensions:
X509v3 Basic Constraints: critical
CA:TRUE
Netscape Cert Type:
SSL CA
X509v3 Extended Key Usage:
TLS Web Server Authentication, TLS Web Client Authentication, E-mail Protection, Time Stamping, Microsoft Individual Code Signing, Microsoft Commercial Code Signing, Microsoft Trust List Signing, Microsoft Server Gated Crypto, Microsoft Encrypted File System, Netscape Server Gated Crypto
X509v3 Key Usage: critical
Certificate Sign, CRL Sign
X509v3 Subject Key Identifier:
03:9C:EC:D3:BD:2A:C4:A8:E8:23:04:F2:AD:69:C9:2E:CF:CE:85:85
Signature Algorithm: sha256WithRSAEncryption
6d:98:36:7e:e6:2f:54:7d:7f:0a:9b:85:d5:ef:e6:c3:c7:df:
c8:c4:1b:3e:78:51:ee:48:8c:c2:0c:ac:8f:89:67:06:22:3f:
fe:05:f4:17:2b:1c:23:0e:53:1f:0e:7b:23:e1:fe:ac:9c:52:
ac:13:11:06:be:00:55:13:36:1a:47:22:29:41:79:f8:ca:8e:
2b:5a:26:57:b6:26:80:da:7d:ac:10:5f:53:b9:00:e4:d9:ed:
51:04:52:af:d0:7c:33:ce:24:6f:eb:06:d0:49:c6:da:71:25:
64:fe:66:0b:29:90:99:7f:b7:c4:3d:f9:17:5b:24:21:ae:7c:
3f:b1:33:b5:af:64:e2:bc:44:d4:41:df:35:ca:45:8a:08:61:
7a:76:8b:4c:7c:23:80:1d:87:97:29:98:78:a3:38:bf:3c:8d:
5c:79:43:64:95:77:4d:50:cb:a2:17:fd:cf:f9:9f:42:b4:d5:
20:8a:2c:12:af:9d:cd:34:b4:be:53:ad:e4:d8:33:bb:fe:7d:
a1:57:e6:cf:b7:a6:30:a2:3d:f6:8f:4d:4b:f6:2b:cc:19:df:
d2:d5:6e:25:d2:92:13:db:60:f9:6c:e4:bc:09:56:07:5a:30:
6f:89:67:1a:e4:93:52:bd:f6:89:ab:1f:71:17:6b:78:97:69:
05:46:a6:2f
-----BEGIN CERTIFICATE-----
MIIDoTCCAomgAwIBAgIGDncpjsZKMA0GCSqGSIb3DQEBCwUAMCgxEjAQBgNVBAMM
CW1pdG1wcm94eTESMBAGA1UECgwJbWl0bXByb3h5MB4XDTIwMDUyNDEyMjgzMVoX
DTIzMDUyNjEyMjgzMVowKDESMBAGA1UEAwwJbWl0bXByb3h5MRIwEAYDVQQKDAlt
aXRtcHJveHkwggEiMA0GCSqGSIb3DQEBAQUAA4IBDwAwggEKAoIBAQDTYCo6i7ya
LPvakDP6oal6llLkc1bIyH+L+KtL4FUuBXVbVU1tWLCCViOs7rrUTrCrjlIlLBLv
/iM79Q0mns0e1Xxae+DGa6+2sM3RW4sS6qHUFXg3hPLRSGF7m8bs4yxBMnIVFdFf
e4cBQIZqz18qDxlxxTcIlIxNGK9dXYCJRukEI/TnhE6X7oGRB8gYXutkOkeewSlQ
LCfHgDW51uxhkd4jrwR9DOhDMlIJyTS6/ZhR73gTLINK6TFu2FNrEnlE6VtwerV5
LgCpn1PzL8Z1sJAbALRQIV7+taM2GMVCzfzVM+QbwSYSBAWV5Zl8Iyrq3vNFfjud
6Valgwdh6d0ZAgMBAAGjgdAwgc0wDwYDVR0TAQH/BAUwAwEB/zARBglghkgBhvhC
AQEEBAMCAgQweAYDVR0lBHEwbwYIKwYBBQUHAwEGCCsGAQUFBwMCBggrBgEFBQcD
BAYIKwYBBQUHAwgGCisGAQQBgjcCARUGCisGAQQBgjcCARYGCisGAQQBgjcKAwEG
CisGAQQBgjcKAwMGCisGAQQBgjcKAwQGCWCGSAGG+EIEATAOBgNVHQ8BAf8EBAMC
AQYwHQYDVR0OBBYEFAOc7NO9KsSo6CME8q1pyS7PzoWFMA0GCSqGSIb3DQEBCwUA
A4IBAQBtmDZ+5i9UfX8Km4XV7+bDx9/IxBs+eFHuSIzCDKyPiWcGIj/+BfQXKxwj
DlMfDnsj4f6snFKsExEGvgBVEzYaRyIpQXn4yo4rWiZXtiaA2n2sEF9TuQDk2e1R
BFKv0HwzziRv6wbQScbacSVk/mYLKZCZf7fEPfkXWyQhrnw/sTO1r2TivETUQd81
ykWKCGF6dotMfCOAHYeXKZh4ozi/PI1ceUNklXdNUMuiF/3P+Z9CtNUgiiwSr53N
NLS+U63k2DO7/n2hV+bPt6Ywoj32j01L9ivMGd/S1W4l0pIT22D5bOS8CVYHWjBv
iWca5JNSvfaJqx9xF2t4l2kFRqYv
-----END CERTIFICATE-----
>> openssl x509 -in mitmproxy-systemb-ca-cert.pem -text
Certificate:
Data:
Version: 3 (0x2)
Serial Number: 15891076851956 (0xe73edfda8f4)
Signature Algorithm: sha256WithRSAEncryption
Issuer: CN=mitmproxy, O=mitmproxy
Validity
Not Before: May 8 10:48:05 2020 GMT
Not After : May 10 10:48:05 2023 GMT
Subject: CN=mitmproxy, O=mitmproxy
Subject Public Key Info:
Public Key Algorithm: rsaEncryption
Public-Key: (2048 bit)
Modulus:
00:d4:27:ef:99:12:9b:84:9d:82:a7:d1:96:e6:fe:
14:cf:a5:1a:d5:95:f5:1f:b3:25:fc:10:df:1a:f1:
20:4a:a5:e9:e9:b9:20:ba:d3:c2:88:e9:cb:fe:66:
43:5e:4a:1d:9c:39:f4:a8:64:50:51:f6:18:0b:f2:
a2:b3:da:1d:a5:0d:01:c5:bd:c0:6c:b7:a7:25:cd:
6d:d7:21:2b:ba:a8:35:b6:a4:a3:33:0d:15:8d:44:
8e:bb:70:d6:1a:9b:c2:21:09:f9:70:fc:42:8c:d6:
a9:1b:d2:d1:0c:4b:03:f2:44:ca:c7:bf:8f:8b:e2:
fe:0c:ff:99:fe:61:f2:8f:6e:26:ae:ec:60:6c:ff:
ec:51:db:3e:3c:3e:a9:32:38:61:13:52:8e:40:15:
b0:8d:f7:7b:b8:d9:11:84:d6:dc:bd:9e:12:58:5c:
03:13:d6:73:6e:95:84:5f:8d:21:72:bb:17:27:a7:
19:b4:00:43:7b:bc:2e:f2:d9:8a:68:53:0d:de:bc:
03:6c:f8:78:c9:e6:43:1f:45:1e:b0:d0:7d:3b:a7:
cc:05:f2:cb:b1:5f:9c:5f:7f:ee:f3:4e:94:99:28:
33:6f:65:eb:24:a2:44:f1:22:13:a7:71:cd:88:15:
c3:14:77:a2:3c:dc:59:6c:10:81:0f:f1:89:ef:90:
1d:b5
Exponent: 65537 (0x10001)
X509v3 extensions:
X509v3 Basic Constraints: critical
CA:TRUE
Netscape Cert Type:
SSL CA
X509v3 Extended Key Usage:
TLS Web Server Authentication, TLS Web Client Authentication, E-mail Protection, Time Stamping, Microsoft Individual Code Signing, Microsoft Commercial Code Signing, Microsoft Trust List Signing, Microsoft Server Gated Crypto, Microsoft Encrypted File System, Netscape Server Gated Crypto
X509v3 Key Usage: critical
Certificate Sign, CRL Sign
X509v3 Subject Key Identifier:
FE:50:10:81:42:BA:C2:85:01:CB:D2:B4:2E:FF:F1:B3:CD:B2:63:16
Signature Algorithm: sha256WithRSAEncryption
00:d0:fe:58:df:07:90:b9:03:25:b9:0c:6d:37:e4:65:aa:0f:
f9:d4:ea:9a:42:b7:3e:0f:8f:d3:1e:c4:26:03:ff:57:5b:6f:
3d:36:fb:cd:61:4f:4a:5a:20:71:5e:96:25:b3:d2:31:4b:da:
ec:6c:6e:30:e9:0f:77:5b:fe:34:95:5d:31:2a:bf:53:b9:f4:
94:98:5c:fa:b9:c5:27:1a:7e:51:2e:dd:75:f5:c6:51:f7:8d:
69:66:77:9c:e6:0f:7c:79:1a:2f:ca:be:16:9e:45:3f:4b:ff:
49:d8:5d:37:5f:d5:2c:f4:cd:bd:06:fd:09:b0:7b:4b:2b:21:
99:40:24:0a:f6:5f:c3:9c:2f:58:f6:60:b6:b4:3c:b6:89:43:
a6:be:a0:4a:9b:d4:2d:06:b3:2c:b3:eb:c6:18:5a:e4:b1:2b:
f7:b3:7a:a6:41:96:1e:09:19:39:37:25:e0:2c:7a:31:aa:bf:
f8:1a:c2:76:9b:32:30:b7:20:28:ea:63:a9:f7:16:ba:4d:23:
a5:90:7c:0f:31:b9:cd:f8:77:64:8f:28:5f:b8:10:64:4d:08:
f8:6a:9c:45:6f:c7:28:2e:4c:2c:34:09:ef:57:ed:c6:0e:c3:
6d:db:a4:de:8c:72:30:2d:59:8d:c1:e1:2c:6d:29:89:d5:9d:
86:c3:fb:65
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----
For example on a freshly installed ubuntu 20.04 box or a fresh container,
issueing the following commands reproduces the issue not only for me:
apt update
apt install mitmproxy
mitmdump
<CTRL-C>
openssl x509 -in /root/.mitmproxy/mitmproxy-ca-cert.pem -hash -issuer_hash
8bbe0e8d
8bbe0e8d
Of course both hashes are the same, it is a self-signed root cert. But I find it surprising that I always get the hash value of 8bbe0e8d. Everywhere.
The answer to solve this riddle is documented in the OpenSSL man page:
-issuer_hash outputs the "hash" of the certificate issuer name.
And as you can see in the output of your certificate the issuer of the certificate is fixed and therefore the same on each and every system mitmproxy is installed: CN=mitmproxy, O=mitmproxy
A fixed input always outputs the same hash value of course.
One Root CA certificate can have multiple child certificates. Hence all those child certificates have the same issuer and therefore are all mapped to the same hash. Therefore it is nothing unusual that multiple certificates in /etc/ssl/certs/ are mapped to the same hash value. This seems to be some sort of grouping.
Using at that point the certificate fingerprint (or the issuer certificate fingerprint) does not make much sense, because when you use /etc/ssl/certs/ usually you want to find exactly the data of this certificate. If you would already know the certificate fingerprint you also have the certificate and hence doe not have to search for the certificate data.