imap-send: increase command size limit

nfvasprintf() has a 8KB limit, but it's not relevant, as its result is
combined with other strings and added to a 1KB buffer by its caller.
That 1KB limit is not mentioned in RFC 9051, which specifies IMAP.

While 1KB is plenty for user names, passwords and mailbox names,
there's no point in limiting our commands like that.  Call xstrvfmt()
instead of open-coding it and use strbuf to format the command to
send, as we need its length.  Fail hard if it exceeds INT_MAX, because
socket_write() can't take more than that.

Suggested-by: Jeff King <peff@peff.net>
Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/imap-send.c b/imap-send.c
index 4caa8668e6ccb410ebf7eabd4245c00ac7fff0aa..0afd088d8a4d3ed1a5da3f469922bbbb0ef3005d 100644 (file)
--- a/imap-send.c
+++ b/imap-send.c
@@ -68,20 +68,6 @@ static void imap_warn(const char *, ...);
 
 static char *next_arg(char **);
 
-static int nfvasprintf(char **strp, const char *fmt, va_list ap)
-{
-       int len;
-       char tmp[8192];
-
-       len = vsnprintf(tmp, sizeof(tmp), fmt, ap);
-       if (len < 0)
-               die("Fatal: Out of memory");
-       if (len >= sizeof(tmp))
-               die("imap command overflow!");
-       *strp = xmemdupz(tmp, len);
-       return len;
-}
-
 struct imap_server_conf {
        const char *name;
        const char *tunnel;
@@ -503,11 +489,11 @@ static struct imap_cmd *issue_imap_cmd(struct imap_store *ctx,
 {
        struct imap *imap = ctx->imap;
        struct imap_cmd *cmd;
-       int n, bufl;
-       char buf[1024];
+       int n;
+       struct strbuf buf = STRBUF_INIT;
 
        cmd = xmalloc(sizeof(struct imap_cmd));
-       nfvasprintf(&cmd->cmd, fmt, ap);
+       cmd->cmd = xstrvfmt(fmt, ap);
        cmd->tag = ++imap->nexttag;
 
        if (cb)
@@ -519,27 +505,30 @@ static struct imap_cmd *issue_imap_cmd(struct imap_store *ctx,
                get_cmd_result(ctx, NULL);
 
        if (!cmd->cb.data)
-               bufl = xsnprintf(buf, sizeof(buf), "%d %s\r\n", cmd->tag, cmd->cmd);
+               strbuf_addf(&buf, "%d %s\r\n", cmd->tag, cmd->cmd);
        else
-               bufl = xsnprintf(buf, sizeof(buf), "%d %s{%d%s}\r\n",
-                                cmd->tag, cmd->cmd, cmd->cb.dlen,
-                                CAP(LITERALPLUS) ? "+" : "");
+               strbuf_addf(&buf, "%d %s{%d%s}\r\n", cmd->tag, cmd->cmd,
+                           cmd->cb.dlen, CAP(LITERALPLUS) ? "+" : "");
+       if (buf.len > INT_MAX)
+               die("imap command overflow!");
 
        if (0 < verbosity) {
                if (imap->num_in_progress)
                        printf("(%d in progress) ", imap->num_in_progress);
                if (!starts_with(cmd->cmd, "LOGIN"))
-                       printf(">>> %s", buf);
+                       printf(">>> %s", buf.buf);
                else
                        printf(">>> %d LOGIN <user> <pass>\n", cmd->tag);
        }
-       if (socket_write(&imap->buf.sock, buf, bufl) != bufl) {
+       if (socket_write(&imap->buf.sock, buf.buf, buf.len) != buf.len) {
                free(cmd->cmd);
                free(cmd);
                if (cb)
                        free(cb->data);
+               strbuf_release(&buf);
                return NULL;
        }
+       strbuf_release(&buf);
        if (cmd->cb.data) {
                if (CAP(LITERALPLUS)) {
                        n = socket_write(&imap->buf.sock, cmd->cb.data, cmd->cb.dlen);