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0001-gpg-Fix-double-free-with-anonymous-recipients.patch
werner (Werner Koch)
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Nov 29 2019, 5:47 PM
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0001-gpg-Fix-double-free-with-anonymous-recipients.patch
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From 9ac182f376abf910a7b737b0e1ebd447eaa582f1 Mon Sep 17 00:00:00 2001
From: Werner Koch <wk@gnupg.org>
Date: Fri, 29 Nov 2019 17:44:12 +0100
Subject: [PATCH GnuPG] gpg: Fix double free with anonymous recipients.
* g10/pubkey-enc.c (get_session_key): Do not release SK.
--
Bug is in 2.2.18 only.
The semantics of the enum_secret_keys function changed in master.
When back porting this for 2.2.18 I missed this change and thus we ran
into a double free. The patches fixes the regression but is it clumsy.
We need to change the enum_secret_keys interface to avoid such a
surprising behaviour; this needs to be done in master first.
Regression-due-to: 9a317557c58d2bdcc504b70c366b77f4cac71df7
GnuPG-bug-id: 4762
Signed-off-by: Werner Koch <wk@gnupg.org>
---
g10/pubkey-enc.c | 8 ++++++--
g10/skclist.c | 7 +++++--
2 files changed, 11 insertions(+), 4 deletions(-)
diff --git a/g10/pubkey-enc.c b/g10/pubkey-enc.c
index 71a48cc41..4e6f893f3 100644
--- a/g10/pubkey-enc.c
+++ b/g10/pubkey-enc.c
@@ -114,11 +114,11 @@ get_session_key (ctrl_t ctrl, PKT_pubkey_enc * k, DEK * dek)
for (;;)
{
- free_public_key (sk);
sk = xmalloc_clear (sizeof *sk);
rc = enum_secret_keys (ctrl, &enum_context, sk);
if (rc)
{
+ sk = NULL; /* enum_secret_keys turns SK into a shallow copy! */
rc = GPG_ERR_NO_SECKEY;
break;
}
@@ -148,10 +148,14 @@ get_session_key (ctrl_t ctrl, PKT_pubkey_enc * k, DEK * dek)
{
if (!opt.quiet)
log_info (_("okay, we are the anonymous recipient.\n"));
+ sk = NULL;
break;
}
else if (gpg_err_code (rc) == GPG_ERR_FULLY_CANCELED)
- break; /* Don't try any more secret keys. */
+ {
+ sk = NULL;
+ break; /* Don't try any more secret keys. */
+ }
}
enum_secret_keys (ctrl, &enum_context, NULL); /* free context */
}
diff --git a/g10/skclist.c b/g10/skclist.c
index 8817ee904..5a32b6a17 100644
--- a/g10/skclist.c
+++ b/g10/skclist.c
@@ -292,14 +292,17 @@ build_sk_list (ctrl_t ctrl,
* --default-key and --try-secret-key). Use the following procedure:
*
* 1) Initialize a void pointer to NULL
- * 2) Pass a reference to this pointer to this function (content)
- * and provide space for the secret key (sk)
+ * 2) Pass a reference to this pointer to this function (CONTEXT)
+ * and provide space for the secret key (SK)
* 3) Call this function as long as it does not return an error (or
* until you are done). The error code GPG_ERR_EOF indicates the
* end of the listing.
* 4) Call this function a last time with SK set to NULL,
* so that can free it's context.
*
+ * TAKE CARE: When the function returns SK belongs to CONTEXT and may
+ * not be freed by the caller; neither on success nor on error.
+ *
* In pseudo-code:
*
* void *ctx = NULL;
--
2.11.0

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