iOS: Support for managing certificate authorities

[baltpeter]

We already have that on Android (tweaselORG/meta#18 (comment)), now we also need to be able to add and remove root CAs on iOS.

[baltpeter]

I've documented the manual install process here: tweaselORG/meta#20 (comment)

[baltpeter]

So, let's see how we can automate that. I would prefer to find a method that doesn't require Frida, but we'll see.

My first approach: How does macOS store the CAs? Maybe it's similar for iOS.

According to https://stackoverflow.com/a/24694579, macOS doesn't have a CA bundle like Linux.

https://support.apple.com/en-us/HT208127 mentions a file /System/Library/Security/Certificates.bundle/Contents/Resources/TrustStore.html. The folder for Certificates.bundle also exists on the iPhone:

root# ls -lh /System/Library/Security/Certificates.bundle
total 6.6M
-rw-r--r-- 1 root wheel  764 Sep  3  2022 AnalyticsSamplingRates.plist
-rw-r--r-- 1 root wheel  499 Sep  3  2022 AppleCertificateAuthorities.plist
-rw-r--r-- 1 root wheel  103 Sep  3  2022 AssetVersion.plist
-rw-r--r-- 1 root wheel  267 Sep  3  2022 Blocked.plist
-rw-r--r-- 1 root wheel  18K Sep  3  2022 CertificatePinning.plist
-rw-r--r-- 1 root wheel 5.5K Sep  3  2022 EVRoots.plist
-rw-r--r-- 1 root wheel  796 Sep  3  2022 Info.plist
-rw-r--r-- 1 root wheel  66K Sep  3  2022 TrustStore.html
-rw-r--r-- 1 root wheel 3.8K Sep  3  2022 TrustedCTLogs.plist
-rw-r--r-- 1 root wheel 3.8K Sep  3  2022 TrustedCTLogs_nonTLS.plist
-rw-r--r-- 1 root wheel   86 Sep  3  2022 ValidUpdate.plist
drwxr-xr-x 6 root wheel  192 Sep  3  2022 _CodeSignature/
-rw-r--r-- 1 root wheel 3.9K Sep  3  2022 certsIndex.data
-rw-r--r-- 1 root wheel 184K Sep  3  2022 certsTable.data
-rw-r--r-- 1 root wheel  362 Sep  3  2022 manifest.data
-rw-r--r-- 1 root wheel 6.3M Sep  3  2022 valid.sqlite3

[baltpeter]

I also checked how you would add a CA on macOS using the command line.

There is a security command for that (https://derflounder.wordpress.com/2011/03/13/adding-new-trusted-root-certificates-to-system-keychain/, https://apple.stackexchange.com/questions/80623/import-certificates-into-the-system-keychain-via-the-command-line). That unfortunately doesn't exist on iOS.

According to https://derflounder.wordpress.com/2011/03/13/adding-new-trusted-root-certificates-to-system-keychain/, the root CAs are stored in /Library/Keychains/System.keychain.

While there is no System.keychain on iOS, there is some stuff there:

root# ls -lh /Library/Keychains 
root wheel 24 Sep  3  2022 /Library/Keychains -> ../private/var/Keychains/
Vanessas-iPhone-2:~ root# ls -lh /private/var/Keychains/ 
total 6.9M
drwxrwxrwx 23 root       wheel  736 Jan 24 14:18 Analytics/
-rw-------  1 _securityd wheel    2 Jan 24 14:04 SOSAccountSettings.pb
-rw-r--r--  1 root       wheel 140K Jan 24 14:04 com.apple.security.keychain-defaultContext.TrustedPeersHelper.db
-rw-r--r--  1 root       wheel  32K Mar  9 13:56 com.apple.security.keychain-defaultContext.TrustedPeersHelper.db-shm
-rw-r--r--  1 root       wheel 149K Mar  9 14:00 com.apple.security.keychain-defaultContext.TrustedPeersHelper.db-wal
-rw-------  1 _securityd wheel 2.4M Mar  9 15:08 keychain-2.db
-rw-------  1 _securityd wheel  32K Mar  9 13:56 keychain-2.db-shm
-rw-------  1 _securityd wheel 2.3M Mar  9 15:34 keychain-2.db-wal
-r--------  1 root       wheel 346K Mar  9 14:27 keychain-ota-backup.plist

[baltpeter]

support.apple.com/en-us/HT208127 mentions a file /System/Library/Security/Certificates.bundle/Contents/Resources/TrustStore.html. The folder for Certificates.bundle also exists on the iPhone

Let's see whether there's anything that helps us there:

• CertificatePinning.plist is certainly interesting, but we don't care about certificate pinning here:

  

• certsTable.data looks like it may well contain the CAs, but I have no idea how to parse (and much less edit) that file:

  

  But it notably doesn't contain the string mitmproxy. These will be the CAs that come bundled with the system and the user-added ones will be somewhere else.

• TrustedCTLogs.plist is (unsurprisingly, given the name) about certificate transparency logs:

  

• TrustStore.html is a rendered table of the system CAs (again, no mitmproxy):

  

• valid.sqlite3 has a bunch of stuff that I don't really understand yet. These are the tables:

  

  admin and dates are boring:

  

  

  Some rows in groups have a blob in the data column:

  

  That is a zlib-ed plist, but I can't really make sense of its content (CyberChef link).

  And I don't know what the blobs in hashes, issuers, or serials are:

  

  

  

[baltpeter]

Next try: I've used an improved version of my SQLite grep script to check if any database on the system contains a string that might be our certificate:

# Adapted after: https://stackoverflow.com/a/53875499 and https://stackoverflow.com/a/29548123
NEEDLE="mitmproxy|begin certificate|MIIDoTCCAomg|IVCc6egf0T"

find / -name '*.db' -o -name '*.sqlite*' -print0 2>/dev/null | while IFS= read -r -d '' file; do
    for X in $(sqlite3 -readonly "$file" .tables 2>/dev/null);
        do sqlite3 -readonly "$file" "SELECT * FROM \"$X\";" 2>/dev/null | grep -iE >/dev/null $NEEDLE && echo "Found in file '$file', table '$X'";
    done
done

Result:

Found in file '/private/var/mobile/Media/PhotoData/Caches/search/psi.sqlite', table 'groups'
Found in file '/private/var/protected/trustd/private/TrustStore.sqlite3', table 'tsettings'

/private/var/mobile/Media/PhotoData/Caches/search/psi.sqlite is clearly a false positive. Seems like it put the name of the profile I downloaded into the photo search cache (for some reason…):

/private/var/protected/trustd/private/TrustStore.sqlite3 (download) is much more relevant:

Values of each column:

sha256:

00000000  e4 87 d9 63 6b 76 9d 45 82 f1 d5 f4 4c bf 23 e9  |ä.Ùckv.E.ñÕôL¿#é|
00000010  85 b6 98 cf 60 b1 41 7d 89 16 47 ff 74 ad 09 6d  |.¶.Ï`±A}..Gÿt..m|

subj:

00000000  31 12 30 10 06 03 55 04 03 0c 09 6d 69 74 6d 70  |1.0...U....mitmp|
00000010  72 6f 78 79 31 12 30 10 06 03 55 04 0a 0c 09 6d  |roxy1.0...U....m|
00000020  69 74 6d 70 72 6f 78 79                          |itmproxy|

tset:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<array/>
</plist>

data:

00000000  30 82 03 a1 30 82 02 89 a0 03 02 01 02 02 06 0e  |0..¡0... .......|
00000010  9a 89 8f 5f b9 30 0d 06 09 2a 86 48 86 f7 0d 01  |..._¹0...*.H.÷..|
00000020  01 0b 05 00 30 28 31 12 30 10 06 03 55 04 03 0c  |....0(1.0...U...|
00000030  09 6d 69 74 6d 70 72 6f 78 79 31 12 30 10 06 03  |.mitmproxy1.0...|
00000040  55 04 0a 0c 09 6d 69 74 6d 70 72 6f 78 79 30 1e  |U....mitmproxy0.|
00000050  17 0d 32 30 31 31 31 36 30 38 35 32 34 32 5a 17  |..201116085242Z.|
00000060  0d 32 33 31 31 31 38 30 38 35 32 34 32 5a 30 28  |.231118085242Z0(|
00000070  31 12 30 10 06 03 55 04 03 0c 09 6d 69 74 6d 70  |1.0...U....mitmp|
00000080  72 6f 78 79 31 12 30 10 06 03 55 04 0a 0c 09 6d  |roxy1.0...U....m|
00000090  69 74 6d 70 72 6f 78 79 30 82 01 22 30 0d 06 09  |itmproxy0.."0...|
000000a0  2a 86 48 86 f7 0d 01 01 01 05 00 03 82 01 0f 00  |*.H.÷...........|
000000b0  30 82 01 0a 02 82 01 01 00 9d 78 98 b9 35 e7 d5  |0.........x.¹5çÕ|
000000c0  79 b3 ba 03 83 e0 de 64 2f 8c ef e7 64 77 76 c0  |y³º..àÞd/.ïçdwvÀ|
000000d0  1b 6b 99 9b e9 d4 16 f9 35 13 64 77 1b 94 c0 8f  |.k..éÔ.ù5.dw..À.|
000000e0  67 0f 47 d2 d8 d8 9e e8 1d 0a e9 84 5f a3 02 28  |g.GÒØØ.è..é._£.(|
000000f0  d5 34 f7 1d 51 60 dc 7c ac 7a 22 e7 f7 7b 57 5f  |Õ4÷.Q`Ü|¬z"ç÷{W_|
00000100  b7 8a c7 bc 5b be fe f9 8d ab 09 5c 5d f4 7a 67  |·.Ǽ[¾þù.«.\]ôzg|
00000110  f4 55 97 45 00 ec 21 a3 fa 27 43 33 76 01 80 42  |ôU.E.ì!£ú'C3v..B|
00000120  2d 3f 62 37 69 be 9c b3 87 53 c1 47 d9 81 fd 42  |-?b7i¾.³.SÁGÙ.ýB|
00000130  db b3 a3 97 85 07 cc 04 72 a8 8b 4d c4 9a eb 7a  |Û³£...Ì.r¨.MÄ.ëz|
00000140  79 cd 40 1e 06 c6 4b b7 c5 77 8e a3 b3 f1 6c dc  |yÍ@..ÆK·Åw.£³ñlÜ|
00000150  f6 ad 70 37 c4 87 96 34 ff 3b d8 a4 23 81 fb 82  |ö.p7Ä..4ÿ;ؤ#.û.|
00000160  9a a7 d5 f9 48 50 4c 55 1e b2 e4 ea 82 58 ea 2c  |.§ÕùHPLU.²äê.Xê,|
00000170  b1 44 df 6b f8 dc 91 c9 4f e9 68 db f5 a8 53 74  |±DßkøÜ.ÉOéhÛõ¨St|
00000180  2c 88 11 b0 77 06 64 f9 1f 93 df b3 27 a9 cc 87  |,..°w.dù..ß³'©Ì.|
00000190  98 50 29 b0 95 8b b2 fb 4e 7d ea e7 96 e4 52 64  |.P)°..²ûN}êç.äRd|
000001a0  a1 37 a7 cc d9 c2 90 fa 56 43 86 21 e3 34 0a a5  |¡7§ÌÙÂ.úVC.!ã4.¥|
000001b0  03 41 8d d5 e6 47 a7 99 63 02 03 01 00 01 a3 81  |.A.ÕæG§.c.....£.|
000001c0  d0 30 81 cd 30 0f 06 03 55 1d 13 01 01 ff 04 05  |Ð0.Í0...U....ÿ..|
000001d0  30 03 01 01 ff 30 11 06 09 60 86 48 01 86 f8 42  |0...ÿ0...`.H..øB|
000001e0  01 01 04 04 03 02 02 04 30 78 06 03 55 1d 25 04  |........0x..U.%.|
000001f0  71 30 6f 06 08 2b 06 01 05 05 07 03 01 06 08 2b  |q0o..+.........+|
00000200  06 01 05 05 07 03 02 06 08 2b 06 01 05 05 07 03  |.........+......|
00000210  04 06 08 2b 06 01 05 05 07 03 08 06 0a 2b 06 01  |...+.........+..|
00000220  04 01 82 37 02 01 15 06 0a 2b 06 01 04 01 82 37  |...7.....+.....7|
00000230  02 01 16 06 0a 2b 06 01 04 01 82 37 0a 03 01 06  |.....+.....7....|
00000240  0a 2b 06 01 04 01 82 37 0a 03 03 06 0a 2b 06 01  |.+.....7.....+..|
00000250  04 01 82 37 0a 03 04 06 09 60 86 48 01 86 f8 42  |...7.....`.H..øB|
00000260  04 01 30 0e 06 03 55 1d 0f 01 01 ff 04 04 03 02  |..0...U....ÿ....|
00000270  01 06 30 1d 06 03 55 1d 0e 04 16 04 14 ad 34 c5  |..0...U.......4Å|
00000280  90 69 f7 55 52 0f d8 b8 5f 28 fa 21 43 ef 05 09  |.i÷UR.ظ_(ú!Cï..|
00000290  0f 30 0d 06 09 2a 86 48 86 f7 0d 01 01 0b 05 00  |.0...*.H.÷......|
000002a0  03 82 01 01 00 58 41 ca a0 3a 91 26 1e 43 02 90  |.....XAÊ :.&.C..|
000002b0  71 84 4d a3 c9 71 d6 e0 e6 67 e1 07 f9 5b 1e 83  |q.M£ÉqÖàægá.ù[..|
000002c0  41 06 e0 ac 68 e5 65 9d f3 e3 9a ec cf ab 24 08  |A.à¬håe.óã.ìÏ«$.|
000002d0  8e 43 61 02 19 6f 60 03 1e a9 3d e6 3c 15 6c 4e  |.Ca..o`..©=æ<.lN|
000002e0  01 b0 c1 fc fb 9e b7 4c 27 23 e4 34 7b 7f a6 03  |.°Áüû.·L'#ä4{.¦.|
000002f0  0d 89 9d c6 a1 b8 ad 7e f4 02 7b 52 23 b9 2c db  |...Æ¡¸.~ô.{R#¹,Û|
00000300  1d f8 6e 44 fc 87 45 f4 29 34 10 82 6d eb 13 9e  |.ønDü.Eô)4..më..|
00000310  35 71 cb 2b 99 c0 ad 18 f7 dc 15 5a 72 6a 12 88  |5qË+.À..÷Ü.Zrj..|
00000320  da 72 48 59 03 a5 d0 94 e9 b4 d0 04 b5 a2 2a f1  |ÚrHY.¥Ð.é´Ð.µ¢*ñ|
00000330  09 36 3e 08 0b 84 e2 52 94 f4 49 54 1b c5 c3 4f  |.6>...âR.ôIT.ÅÃO|
00000340  b5 23 73 1f 68 39 43 a3 0f a2 b2 3b 32 14 c0 df  |µ#s.h9C£.¢²;2.Àß|
00000350  89 0c b8 32 09 36 b7 6a 9f 3a 16 5c 98 2f b1 9a  |..¸2.6·j.:.\./±.|
00000360  24 0a 8b 55 68 a2 41 dc 85 26 c0 61 fa ad d6 4b  |$..Uh¢AÜ.&Àaú.ÖK|
00000370  ca ab c7 8f 69 7d f5 68 6b 4b dd ab f4 e6 b8 a1  |Ê«Ç.i}õhkKÝ«ô渡|
00000380  fd 6f 7c 6e 59 bf fb 35 bf 8a f3 34 f0 54 d7 bb  |ýo|nY¿û5¿.ó4ðT×»|
00000390  1c 22 3f bc e4 37 29 08 95 d0 a0 bc d3 f2 15 09  |."?¼ä7)..Р¼Óò..|
000003a0  ce 9e 81 fd 13                                   |Î..ý.|

[baltpeter]

CyberChef detected the data value as application/pkix-cert (cer,cat,p7b,p7c,p7m,p7s,swz,rsa,crl,crt,der)!

[baltpeter]

We can get that really easily using openssl:

openssl x509 -outform der -in ~/.mitmproxy/mitmproxy-ca-cert.pem -out mitmproxy-ca-cert.crt

[baltpeter]

sha256 is just the sha256 hash of the .crt:

❯ sha256sum mitmproxy-ca-cert.crt
e487d9636b769d4582f1d5f44cbf23e985b698cf60b1417d891647ff74ad096d  mitmproxy-ca-cert.crt

[baltpeter]

subj really shouldn't be hard either. Clearly, it's some version of the subject name of the certificate. And I'm pretty sure the exact bytes are already contained in the certificate. Now, I just need a way to extract them for an arbitrary cert.

[baltpeter]

Before I sink too much time into this, let's see whether I'm even on the right track (though I am pretty confident :D).

On the other iPhone, I have not yet installed the CA. Settings -> General -> About -> Certificate Trust Settings shows no user certificates. And indeed, the tsettings table of /private/var/protected/trustd/private/TrustStore.sqlite3 is empty there.

If I copy the database with the mitmproxy cert from the other phone, now the mitmproxy cert does show up but is not trusted:

So, I am definitely on the right track. \o/

[baltpeter]

Looks like somebody else already figured this out: https://github.com/ADVTOOLS/ADVTrustStore :( :D

[baltpeter]

Here's how they get the subj value:

https://github.com/ADVTOOLS/ADVTrustStore/blob/6a90c4f44a2fc02821a6340eb004fc56bf6205d2/iosCertTrustManager.py#L383-L424

Looks like there is no command in openssl that can do that natively (they do call openssl in other places).

[baltpeter]

I've found PKI.js.

As a reminder, we want:

00000000  31 12 30 10 06 03 55 04 03 0c 09 6d 69 74 6d 70  |1.0...U....mitmp|
00000010  72 6f 78 79 31 12 30 10 06 03 55 04 0a 0c 09 6d  |roxy1.0...U....m|
00000020  69 74 6d 70 72 6f 78 79                          |itmproxy|

With this, I'm almost there:

import { readFile } from 'fs/promises';
import * as pkijs from 'pkijs';

(async () => {
    const certDer = await readFile('mitmproxy-ca-cert.crt');

    const c = pkijs.Certificate.fromBER(certDer);
    console.log(c.subject.valueBeforeDecode);
})();

This outputs:

ArrayBuffer {
  [Uint8Contents]: <30 28 31 12 30 10 06 03 55 04 03 0c 09 6d 69 74 6d 70 72 6f 78 79 31 12 30 10 06 03 55 04 0a 0c 09 6d 69 74 6d 70 72 6f 78 79>,
  byteLength: 42
}

There's just two extra bytes at the beginning.