From c9343bec83e2c2a14b564b8a13998806eab1ae9f Mon Sep 17 00:00:00 2001
From: Werner Koch <wk@gnupg.org>
Date: Mon, 15 Nov 2021 17:51:01 +0100
Subject: [PATCH] sm: Detect circular chains in --list-chain.

* sm/keylist.c (list_cert_chain): Break loop for a too long chain.
--

This avoids endless loops in case of circular chain definitions.  We
use such a limit at other palces as well.  Example for such a chain is

# ------------------------ >8 ------------------------
           ID: 0xBE231B05
          S/N: 51260A931CE27F9CC3A55F79E072AE82
        (dec): 107864989418777835411218143713715990146
       Issuer: CN=UTN - DATACorp SGC,OU=http://www.usertrust.com,O=The USERTRUST Network,L=Salt Lake City,ST=UT,C=US
      Subject: CN=AddTrust External CA Root,OU=AddTrust External TTP Network,O=AddTrust AB,C=SE
     sha2_fpr: 92:5E:4B:37:2B:A3:2E:5E:87:30:22:84:B2:D7:C9:DF:BF:82:00:FF:CB:A0:D1:66:03:A1:A0:6F:F7:6C:D3:53
     sha1_fpr: 31:93:78:6A:48:BD:F2:D4:D2:0B:8F:C6:50:1F:4D:E8:BE:23:1B:05
      md5_fpr: AC:F3:10:0D:1A:96:A9:2E:B8:8B:9B:F8:7E:09:FA:E6
      pgp_fpr: E8D2CA1449A80D784FB1532C06B1611DB06A1678
       certid: 610C27E9D37835A8962EA5B8368D3FBED1A8A15D.51260A931CE27F9CC3A55F79E072AE82
      keygrip: CFCA58448222ECAAF77EEF8CC45F0D6DB4E412C9
    notBefore: 2005-06-07 08:09:10
     notAfter: 2019-06-24 19:06:30
     hashAlgo: 1.2.840.113549.1.1.5 (sha1WithRSAEncryption)
      keyType: rsa2048
    subjKeyId: ADBD987A34B426F7FAC42654EF03BDE024CB541A
    authKeyId: [none]
 authKeyId.ki: 5332D1B3CF7FFAE0F1A05D854E92D29E451DB44F
[...]

Certified by
           ID: 0xCE2E4C63
          S/N: 46EAF096054CC5E3FA65EA6E9F42C664
        (dec): 94265836834010752231943569188608722532
       Issuer: CN=AddTrust External CA Root,OU=AddTrust External TTP Network,O=AddTrust AB,C=SE
      Subject: CN=UTN - DATACorp SGC,OU=http://www.usertrust.com,O=The USERTRUST Network,L=Salt Lake City,ST=UT,C=US
     sha2_fpr: 21:3F:AD:03:B1:C5:23:47:E9:A8:0F:29:9A:F0:89:9B:CA:FF:3F:62:B3:4E:B0:60:66:F4:D7:EE:A5:EE:1A:73
     sha1_fpr: 9E:99:81:7D:12:28:0C:96:77:67:44:30:49:2E:DA:1D:CE:2E:4C:63
      md5_fpr: 55:07:0F:1F:9A:E5:EA:21:61:F3:72:2B:8B:41:7F:27
      pgp_fpr: 922A6D0A1C0027E75038F8A1503DA72CF2C53840
       certid: 14673DA5792E145E9FA1425F9EF3BFC1C4B4957C.46EAF096054CC5E3FA65EA6E9F42C664
      keygrip: 10678FB5A458D99B7692851E49849F507688B847
    notBefore: 2005-06-07 08:09:10
     notAfter: 2020-05-30 10:48:38
     hashAlgo: 1.2.840.113549.1.1.5 (sha1WithRSAEncryption)
      keyType: rsa2048
    subjKeyId: 5332D1B3CF7FFAE0F1A05D854E92D29E451DB44F
    authKeyId: [none]
 authKeyId.ki: ADBD987A34B426F7FAC42654EF03BDE024CB541A
     keyUsage: certSign crlSign
[...]

Which has a circular dependency on subKeyId/authkeyId.ki.
---
 sm/keylist.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/sm/keylist.c b/sm/keylist.c
index e0b681f3d..4f2d009fd 100644
--- a/sm/keylist.c
+++ b/sm/keylist.c
@@ -1363,6 +1363,7 @@ list_cert_chain (ctrl_t ctrl, KEYDB_HANDLE hd,
                  estream_t fp, int with_validation)
 {
   ksba_cert_t next = NULL;
+  int depth = 0;
 
   if (raw_mode)
     list_cert_raw (ctrl, hd, cert, fp, 0, with_validation);
@@ -1371,8 +1372,13 @@ list_cert_chain (ctrl_t ctrl, KEYDB_HANDLE hd,
   ksba_cert_ref (cert);
   while (!gpgsm_walk_cert_chain (ctrl, cert, &next))
     {
-      ksba_cert_release (cert);
       es_fputs ("Certified by\n", fp);
+      if (++depth > 50)
+        {
+          es_fputs (_("certificate chain too long\n"), fp);
+          break;
+        }
+      ksba_cert_release (cert);
       if (raw_mode)
         list_cert_raw (ctrl, hd, next, fp, 0, with_validation);
       else