101 lines
3.4 KiB
Diff
101 lines
3.4 KiB
Diff
commit b99de751dd35360c0fccac74a40f4a60dbf1ceea
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Author: Greg Hudson <ghudson@mit.edu>
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Date: Mon Oct 17 20:25:11 2022 -0400
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Fix integer overflows in PAC parsing
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In krb5_parse_pac(), check for buffer counts large enough to threaten
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integer overflow in the header length and memory length calculations.
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Avoid potential integer overflows when checking the length of each
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buffer. Credit to OSS-Fuzz for discovering one of the issues.
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CVE-2022-42898:
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In MIT krb5 releases 1.8 and later, an authenticated attacker may be
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able to cause a KDC or kadmind process to crash by reading beyond the
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bounds of allocated memory, creating a denial of service. A
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privileged attacker may similarly be able to cause a Kerberos or GSS
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application service to crash. On 32-bit platforms, an attacker can
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also cause insufficient memory to be allocated for the result,
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potentially leading to remote code execution in a KDC, kadmind, or GSS
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or Kerberos application server process. An attacker with the
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privileges of a cross-realm KDC may be able to extract secrets from a
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KDC process's memory by having them copied into the PAC of a new
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ticket.
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(cherry picked from commit ea92d2f0fcceb54a70910fa32e9a0d7a5afc3583)
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ticket: 9074
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version_fixed: 1.20.1
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diff --git a/src/lib/krb5/krb/pac.c b/src/lib/krb5/krb/pac.c
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index 2f1df8d42b..f6c4373de0 100644
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--- a/src/lib/krb5/krb/pac.c
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+++ b/lib/krb5/krb/pac.c
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@@ -28,6 +28,8 @@
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#include "int-proto.h"
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#include "authdata.h"
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+#define MAX_BUFFERS 4096
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+
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/* draft-brezak-win2k-krb-authz-00 */
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/*
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@@ -317,6 +319,9 @@ krb5_pac_parse(krb5_context context,
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if (version != 0)
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return EINVAL;
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+ if (cbuffers < 1 || cbuffers > MAX_BUFFERS)
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+ return ERANGE;
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+
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header_len = PACTYPE_LENGTH + (cbuffers * PAC_INFO_BUFFER_LENGTH);
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if (len < header_len)
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return ERANGE;
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@@ -349,8 +354,8 @@ krb5_pac_parse(krb5_context context,
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krb5_pac_free(context, pac);
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return EINVAL;
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}
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- if (buffer->Offset < header_len ||
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- buffer->Offset + buffer->cbBufferSize > len) {
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+ if (buffer->Offset < header_len || buffer->Offset > len ||
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+ buffer->cbBufferSize > len - buffer->Offset) {
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krb5_pac_free(context, pac);
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return ERANGE;
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}
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diff --git a/src/lib/krb5/krb/t_pac.c b/src/lib/krb5/krb/t_pac.c
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index 0b1b1f0564..173bde7bab 100644
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--- a/src/lib/krb5/krb/t_pac.c
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+++ b/lib/krb5/krb/t_pac.c
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@@ -431,6 +431,16 @@ static const unsigned char s4u_pac_ent_xrealm[] = {
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0x8a, 0x81, 0x9c, 0x9c, 0x00, 0x00, 0x00, 0x00
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};
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+static const unsigned char fuzz1[] = {
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+ 0x00, 0x00, 0x00, 0x10, 0x00, 0x00, 0x00, 0x00,
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+ 0x06, 0xff, 0xff, 0xff, 0x00, 0x00, 0xf5
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+};
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+
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+static const unsigned char fuzz2[] = {
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+ 0x00, 0x00, 0x00, 0x20, 0x00, 0x00, 0x00, 0x00,
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+ 0x20, 0x20
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+};
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+
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static const char *s4u_principal = "w2k8u@ACME.COM";
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static const char *s4u_enterprise = "w2k8u@abc@ACME.COM";
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@@ -828,6 +838,14 @@ main(int argc, char **argv)
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krb5_free_principal(context, sep);
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}
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+ /* Check problematic PACs found by fuzzing. */
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+ ret = krb5_pac_parse(context, fuzz1, sizeof(fuzz1), &pac);
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+ if (!ret)
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+ err(context, ret, "krb5_pac_parse should have failed");
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+ ret = krb5_pac_parse(context, fuzz2, sizeof(fuzz2), &pac);
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+ if (!ret)
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+ err(context, ret, "krb5_pac_parse should have failed");
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+
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/*
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* Test empty free
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*/
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