--- /dev/null
+From 889894461aa958da4604299acc161c29e2aa603c Mon Sep 17 00:00:00 2001
+From: Jeremy Harris <jgh146exb@wizmail.org>
+Date: Sun, 5 Sep 2021 11:32:09 +0100
+Subject: [PATCH] Fix validation of domain-literals in Message_ID: headers.
+ Bug 2805
+
+---
+ src/src/parse.c | 34 +++++++++++++++++++++-------------
+ src/src/receive.c | 3 ++-
+ 5 files changed, 43 insertions(+), 20 deletions(-)
+
+diff --git a/src/src/parse.c b/src/src/parse.c
+index 58f8941..42f1234 100644
+--- a/src/src/parse.c
++++ b/src/src/parse.c
+@@ -224,16 +224,20 @@ If allow_domain_literals is TRUE, a "domain" may also be an IP address enclosed
+ in []. Make sure the output is set to the null string if there is a syntax
+ error as well as if there is no domain at all.
+
++Optionally, msg_id domain literals ( printable-ascii enclosed in [] )
++are permitted.
++
+ Arguments:
+ s current character pointer
+ t where to put the domain
++ msg_id_literals flag for relaxed domain-literal processing
+ errorptr put error message here on failure (*t will be 0 on exit)
+
+ Returns: new character pointer
+ */
+
+ static const uschar *
+-read_domain(const uschar *s, uschar *t, uschar **errorptr)
++read_domain(const uschar *s, uschar *t, BOOL msg_id_literals, uschar **errorptr)
+ {
+ uschar *tt = t;
+ s = skip_comment(s);
+@@ -259,7 +263,11 @@ if (*s == '[')
+ t += 5;
+ s += 5;
+ }
+- while (*s == '.' || *s == ':' || isxdigit(*s)) *t++ = *s++;
++
++ if (msg_id_literals)
++ while (*s >= 33 && *s <= 90 || *s >= 94 && *s <= 126) *t++ = *s++;
++ else
++ while (*s == '.' || *s == ':' || isxdigit(*s)) *t++ = *s++;
+
+ if (*s == ']') *t++ = *s++; else
+ {
+@@ -267,7 +275,7 @@ if (*s == '[')
+ *tt = 0;
+ }
+
+- if (!allow_domain_literals)
++ if (!allow_domain_literals && !msg_id_literals)
+ {
+ *errorptr = US"domain literals not allowed";
+ *tt = 0;
+@@ -500,7 +508,7 @@ BOOL commas = FALSE;
+ while (*s == '@')
+ {
+ *t++ = '@';
+- s = read_domain(s+1, t, errorptr);
++ s = read_domain(s+1, t, FALSE, errorptr);
+ if (*t == 0) return s;
+ t += Ustrlen((const uschar *)t);
+ if (*s != ',') break;
+@@ -559,7 +567,7 @@ if (*errorptr == NULL)
+ t += Ustrlen((const uschar *)t);
+ *t++ = *s++;
+ *domainptr = t;
+- s = read_domain(s, t, errorptr);
++ s = read_domain(s, t, FALSE, errorptr);
+ }
+ return s;
+ }
+@@ -649,7 +657,7 @@ if (*s != '@' && *s != '<')
+ {
+ if (*s == 0 || *s == ';')
+ {
+- if (*t == 0) FAILED(US"empty address");
++ if (!*t) FAILED(US"empty address");
+ endptr = last_comment_position;
+ goto PARSE_SUCCEEDED; /* Bare local part */
+ }
+@@ -740,7 +748,7 @@ if (*s == '<')
+ }
+
+ endptr = s;
+- if (*errorptr != NULL) goto PARSE_FAILED;
++ if (*errorptr) goto PARSE_FAILED;
+ while (bracket_count-- > 0) if (*s++ != '>')
+ {
+ *errorptr = s[-1] == 0
+@@ -759,14 +767,14 @@ should be the domain. However, for flexibility we allow for a route-address
+ not enclosed in <> as well, which is indicated by an empty first local
+ part preceding '@'. The source routing is, however, ignored. */
+
+-else if (*t == 0)
++else if (!*t)
+ {
+ uschar *domainptr = yield;
+ s = read_route(s, t, errorptr);
+- if (*errorptr != NULL) goto PARSE_FAILED;
++ if (*errorptr) goto PARSE_FAILED;
+ *t = 0; /* Ensure route is ignored - probably overkill */
+ s = read_addr_spec(s, t, 0, errorptr, &domainptr);
+- if (*errorptr != NULL) goto PARSE_FAILED;
++ if (*errorptr) goto PARSE_FAILED;
+ *domain = domainptr - yield;
+ endptr = last_comment_position;
+ if (*domain == 0) FAILED(US"domain missing in source-routed address");
+@@ -779,8 +787,8 @@ else
+ t += Ustrlen((const uschar *)t);
+ *t++ = *s++;
+ *domain = t - yield;
+- s = read_domain(s, t, errorptr);
+- if (*t == 0) goto PARSE_FAILED;
++ s = read_domain(s, t, TRUE, errorptr);
++ if (!*t) goto PARSE_FAILED;
+ endptr = last_comment_position;
+ }
+
+@@ -789,7 +797,7 @@ through for other cases. Endptr may have been moved over whitespace, so
+ move it back past white space if necessary. */
+
+ PARSE_SUCCEEDED:
+-if (*s != 0)
++if (*s)
+ {
+ if (f.parse_found_group && *s == ';')
+ {
+diff --git a/src/src/receive.c b/src/src/receive.c
+index c2b313c..5471aa7 100644
+--- a/src/src/receive.c
++++ b/src/src/receive.c
+@@ -1663,7 +1663,6 @@ int process_info_len = Ustrlen(process_info);
+ int error_rc = error_handling == ERRORS_SENDER
+ ? errors_sender_rc : EXIT_FAILURE;
+ int header_size = 256;
+-int start, end, domain;
+ int id_resolution = 0;
+ int had_zero = 0;
+ int prevlines_length = 0;
+@@ -4084,6 +4083,8 @@ if ( LOGGING(msg_id) && msgid_header
+ uschar * old_id;
+ BOOL save_allow_domain_literals = allow_domain_literals;
+ allow_domain_literals = TRUE;
++ int start, end, domain;
++
+ old_id = parse_extract_address(Ustrchr(msgid_header->text, ':') + 1,
+ &errmsg, &start, &end, &domain, FALSE);
+ allow_domain_literals = save_allow_domain_literals;
+