fix two parsing bugs in imapserver

these could cause the parser to reject correct commands.

the first bug is about the allowed chars for an "atom", we were accepting too
many. this probably isn't easily triggered in practice.

the second bug is about how numbers (digits) are parsed. when gathering digits
to parse as number, we didn't consider only the directly upcoming digits that
make up the number, but continued looking for digits later on in the command.
then we tried to parse a string that was too long as a number, which would fail
because of additional characters. this could have been triggered with commands
containing two numbers. this is possible with e.g. "tag search or larger 123
smaller 123", the "or" takes two search keys again, each with a number. not too
common, but can happen.

found while writing tests for upcoming condstore/qresync implementation.

imapserver/parse.go

@@ -12,12 +12,13 @@ import (
 )
 
 var (
-	listWildcards = "%*"
-	char          = charRange('\x01', '\x7f')
-	ctl           = charRange('\x01', '\x19')
-	atomChar      = charRemove(char, "(){ "+listWildcards+ctl)
-	respSpecials  = atomChar + "]"
-	astringChar   = atomChar + respSpecials
+	listWildcards  = "%*"
+	char           = charRange('\x01', '\x7f')
+	ctl            = charRange('\x01', '\x19')
+	quotedSpecials = `"\`
+	respSpecials   = "]"
+	atomChar       = charRemove(char, "(){ "+ctl+listWildcards+quotedSpecials+respSpecials)
+	astringChar    = atomChar + respSpecials
 )
 
 func charRange(first, last rune) string {
@@ -122,7 +123,7 @@ func (p *parser) take(s string) bool {
 
 func (p *parser) xtake(s string) {
 	if !p.take(s) {
-		p.xerrorf("expected %q", s)
+		p.xerrorf("expected %s", s)
 	}
 }
 
@@ -201,9 +202,10 @@ func (p *parser) xspace() {
 func (p *parser) digits() string {
 	var n int
 	for _, c := range p.upper[p.o:] {
-		if c >= '0' && c <= '9' {
-			n++
+		if c < '0' || c > '9' {
+			break
 		}
+		n++
 	}
 	if n == 0 {
 		return ""

imapserver/search_test.go

@@ -212,6 +212,9 @@ func TestSearch(t *testing.T) {
 	tc.transactf("ok", `search uid 5`)
 	tc.xsearch(1)
 
+	tc.transactf("ok", `search or larger 1000000 smaller 1`)
+	tc.xsearch()
+
 	tc.transactf("ok", `search undraft`)
 	tc.xsearch(1, 2)
 

imapserver/server_test.go

@@ -191,6 +191,7 @@ func (tc *testconn) xcodeArg(v any) {
 }
 
 func (tc *testconn) xuntagged(exps ...any) {
+	tc.t.Helper()
 	tc.xuntaggedCheck(true, exps...)
 }