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net_imap: Allow APPEND to remote servers.
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Previously, the APPEND command could only be used locally,
and attempts to use it remotely would be rejected.
It is now compatible with the transparent client proxy
functionality.
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@InterLinked1
InterLinked1 committed Apr 26, 2024
1 parent c0b8add commit 71b2cd8
Showing 1 changed file with 129 additions and 57 deletions.
186 changes: 129 additions & 57 deletions nets/net_imap.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2379,12 +2379,14 @@ static int handle_append(struct imap_session *imap, char *s)

SHIFT_OPTIONALLY_QUOTED_ARG(mailbox, s);
STRIP_QUOTES(mailbox);
if (imap_translate_dir(imap, mailbox, appenddir, sizeof(appenddir), &destacl)) { /* Destination directory doesn't exist. */
imap_reply(imap, "NO [TRYCREATE] No such mailbox");
return 0;
}

IMAP_REQUIRE_ACL(destacl, IMAP_ACL_INSERT);
if (!imap->client) {
if (imap_translate_dir(imap, mailbox, appenddir, sizeof(appenddir), &destacl)) { /* Destination directory doesn't exist. */
imap_reply(imap, "NO [TRYCREATE] No such mailbox");
return 0;
}
IMAP_REQUIRE_ACL(destacl, IMAP_ACL_INSERT);
}

/* APPEND will clobber the readline buffer, so save off the tag */
safe_strncpy(tag, imap->tag, sizeof(tag));
Expand All @@ -2394,7 +2396,7 @@ static int handle_append(struct imap_session *imap, char *s)
unsigned long quotaleft;
int appendsize, appendfile, appendflags = 0;
ssize_t res;
char *flags, *sizestr;
char *flags = NULL, *sizestr;
char *appenddate = NULL;
int synchronizing;
char appendtmp[260]; /* APPEND tmp name */
Expand All @@ -2415,6 +2417,10 @@ static int handle_append(struct imap_session *imap, char *s)
return -1;
}
s = imap->rldata->buf;
if (imap->client && !(imap->client->virtcapabilities & IMAP_CAPABILITY_MULTIAPPEND)) {
bbs_warning("Client attempting to use MULTIAPPEND but remote server doesn't support it!\n");
break;
}
}

sizestr = strchr(s, '{');
Expand All @@ -2424,6 +2430,7 @@ static int handle_append(struct imap_session *imap, char *s)
}
*sizestr++ = '\0';
synchronizing = strchr(sizestr, '+') ? 0 : 1;
appendsize = atoi(sizestr); /* Read this many bytes */

/* To properly handle the case without flags or date,
* e.g. APPEND "INBOX" {1290}
Expand Down Expand Up @@ -2468,61 +2475,108 @@ static int handle_append(struct imap_session *imap, char *s)
}
}

quotaleft = mailbox_quota_remaining(imap->mbox); /* Calculate current quota remaining to determine acceptance. */
appendsize = atoi(sizestr); /* Read this many bytes */
if (appendsize <= 0) {
imap_reply(imap, "NO [CLIENTBUG] Invalid message literal size");
goto cleanup2;
} else if ((unsigned int) appendsize >= max_append_size) {
if (!synchronizing) {
/* Read and ignore this many bytes, so we don't interpret all those bytes as potential commands afterwards.
* This is to avoid leaving the message in the buffer and trying to parse it all as IMAP commands,
* which would result in spamming the logs, and also present a security risk if any of the lines in the message
* is a potentially valid IMAP command. */
bbs_readline_discard_n(imap->node->rfd, imap->rldata, SEC_MS(10), (size_t) (appendsize + 2)); /* Read the bytes + trailing CR LF and throw them away */
bbs_debug(5, "Discarded %d bytes\n", appendsize);
/* This is obviously wasteful of bandwidth. Client should've supported the APPENDLIMIT extension, though,
* so I'm not sympathetic. Get with the program already, know your limits! */
/* The reason for not sending the NO until afterwards is to guarantee the client won't stop sending
* the message before we receive all of it. Even though that would save bandwidth, that would
* confuse our ability to parse the message properly and be certain of the client's state. */
imap_reply(imap, "NO [LIMIT] Message too large"); /* [TOOBIG] could also be appropriate */
continue; /* Don't disconnect the client, otherwise Thunderbird won't display the [NO] message. For MULTIAPPEND, repeat for all. */
} else {
imap_reply(imap, "NO [LIMIT] Message too large");
goto cleanup;
if (imap->client) {
char remote_cmd[256];
int remote_cmd_len;

/* APPEND to remote IMAP server */

int replacecount = imap_substitute_remote_command(imap->client, mailbox);
if (replacecount != 1) {
/* Shouldn't happen */
imap_reply(imap, "NO Can't append to remote server");
return 0;
}
} else if ((unsigned long) appendsize >= quotaleft) {
if (!synchronizing) {
bbs_readline_discard_n(imap->node->rfd, imap->rldata, SEC_MS(10), (size_t) (appendsize + 2));
bbs_debug(5, "Discarded %d bytes\n", appendsize + 2);
imap_reply(imap, "NO [OVERQUOTA] Insufficient quota remaining");
continue;
} else {
imap_reply(imap, "NO [OVERQUOTA] Insufficient quota remaining");
goto cleanup;

/* Send APPEND to remote server and get response to synchronizing literal, if needed */
remote_cmd_len = snprintf(remote_cmd, sizeof(remote_cmd), "%s APPEND \"%s\" %s%s%s%s%s {%d%s}\r\n",
tag, mailbox,
flags ? "(" : "", S_IF(flags), flags ? ")" : "",
!strlen_zero(appenddate) ? " " : "", S_IF(appenddate),
appendsize,
synchronizing || !(imap->client->virtcapabilities & IMAP_CAPABILITY_LITERAL_PLUS) ? "" : "+");
imap_debug(6, "==> %s", remote_cmd); /* Already includes CR LF */
if (bbs_write(imap->client->client.wfd, remote_cmd, (size_t) remote_cmd_len) < 0) {
return -1;
}
if (synchronizing || !(imap->client->virtcapabilities & IMAP_CAPABILITY_LITERAL_PLUS)) {
res = bbs_readline(imap->client->client.rfd, &imap->client->client.rldata, "\r\n", SEC_MS(1));
if (res < 0) {
/* No need to clean up, since for remote server,
* we're not appending seqnos/UIDs to a uintlist */
return -1;
}
if (strncmp(imap->client->client.buf, "+", 1)) {
bbs_warning("Unexpected response to APPEND: %s\n", imap->client->client.buf);
return -1;
}
if (synchronizing) {
_imap_reply(imap, "+ Ready for literal data\r\n"); /* Synchronizing literal response */
}
}
}

appendfile = maildir_mktemp(appenddir, appendtmp, sizeof(appendtmp), appendnew);
if (appendfile < 0) {
goto cleanup2;
}
/* Ready to receive message from client and proxy it to the remote server */
res = bbs_readline_getn(imap->node->rfd, imap->client->client.wfd, imap->rldata, 5000, (size_t) appendsize);
if (res != appendsize) {
bbs_warning("Client wanted to append %d bytes, but sent %lu?\n", appendsize, res);
return -1; /* Disconnect if we failed to receive the upload properly, since we're probably all screwed up now */
}
} else {
quotaleft = mailbox_quota_remaining(imap->mbox); /* Calculate current quota remaining to determine acceptance. */
if (appendsize <= 0) {
imap_reply(imap, "NO [CLIENTBUG] Invalid message literal size");
goto cleanup2;
} else if ((unsigned int) appendsize >= max_append_size) {
if (!synchronizing) {
/* Read and ignore this many bytes, so we don't interpret all those bytes as potential commands afterwards.
* This is to avoid leaving the message in the buffer and trying to parse it all as IMAP commands,
* which would result in spamming the logs, and also present a security risk if any of the lines in the message
* is a potentially valid IMAP command. */
bbs_readline_discard_n(imap->node->rfd, imap->rldata, SEC_MS(10), (size_t) (appendsize + 2)); /* Read the bytes + trailing CR LF and throw them away */
bbs_debug(5, "Discarded %d bytes\n", appendsize);
/* This is obviously wasteful of bandwidth. Client should've supported the APPENDLIMIT extension, though,
* so I'm not sympathetic. Get with the program already, know your limits! */
/* The reason for not sending the NO until afterwards is to guarantee the client won't stop sending
* the message before we receive all of it. Even though that would save bandwidth, that would
* confuse our ability to parse the message properly and be certain of the client's state. */
imap_reply(imap, "NO [LIMIT] Message too large"); /* [TOOBIG] could also be appropriate */
continue; /* Don't disconnect the client, otherwise Thunderbird won't display the [NO] message. For MULTIAPPEND, repeat for all. */
} else {
imap_reply(imap, "NO [LIMIT] Message too large");
goto cleanup;
}
} else if ((unsigned long) appendsize >= quotaleft) {
if (!synchronizing) {
bbs_readline_discard_n(imap->node->rfd, imap->rldata, SEC_MS(10), (size_t) (appendsize + 2));
bbs_debug(5, "Discarded %d bytes\n", appendsize + 2);
imap_reply(imap, "NO [OVERQUOTA] Insufficient quota remaining");
continue;
} else {
imap_reply(imap, "NO [OVERQUOTA] Insufficient quota remaining");
goto cleanup;
}
}

if (synchronizing) {
_imap_reply(imap, "+ Ready for literal data\r\n"); /* Synchronizing literal response */
}
res = bbs_readline_getn(imap->node->rfd, appendfile, imap->rldata, 5000, (size_t) appendsize);
if (res != appendsize) {
bbs_warning("Client wanted to append %d bytes, but sent %lu?\n", appendsize, res);
appendfile = maildir_mktemp(appenddir, appendtmp, sizeof(appendtmp), appendnew);
if (appendfile < 0) {
goto cleanup2;
}

if (synchronizing) {
_imap_reply(imap, "+ Ready for literal data\r\n"); /* Synchronizing literal response */
}
res = bbs_readline_getn(imap->node->rfd, appendfile, imap->rldata, 5000, (size_t) appendsize);
if (res != appendsize) {
bbs_warning("Client wanted to append %d bytes, but sent %lu?\n", appendsize, res);
close(appendfile);
unlink(appendnew);
goto cleanup2; /* Disconnect if we failed to receive the upload properly, since we're probably all screwed up now */
}
close(appendfile);
unlink(appendnew);
goto cleanup2; /* Disconnect if we failed to receive the upload properly, since we're probably all screwed up now */
}
close(appendfile);
if (process_append(imap, appenddir, appendtmp, appendnew, appenddate, appendflags, &uidvalidity, &uidnext, &a, &lengths, &allocsizes)) {
imap_reply(imap, "NO [SERVERBUG] Append failed");
goto cleanup;
if (process_append(imap, appenddir, appendtmp, appendnew, appenddate, appendflags, &uidvalidity, &uidnext, &a, &lengths, &allocsizes)) {
imap_reply(imap, "NO [SERVERBUG] Append failed");
goto cleanup;
}
}

/* XXX RFC 3502 says MULTIAPPEND should be atomic, but this is not.
Expand All @@ -2533,6 +2587,24 @@ static int handle_append(struct imap_session *imap, char *s)
* that isn't the spirit of an "atomic" operation... */
}

if (imap->client) {
/* Send empty line to denote end of APPEND/MULTIAPPEND */
ssize_t res = bbs_write(imap->client->client.wfd, "\r\n", 2);
if (res < 0) {
return -1;
}
/* Relay response from remote, and no need to clean up */
res = bbs_readline(imap->client->client.rfd, &imap->client->client.rldata, "\r\n", SEC_MS(5));
if (res < 0) {
/* No need to clean up, since for remote server,
* we're not appending seqnos/UIDs to a uintlist */
bbs_warning("APPEND tagged response not received from remote server?\n");
return -1;
}
_imap_reply(imap, "%s\r\n", imap->client->client.buf);
return 0;
}

append_response(imap, imap->acl, a, appends, uidvalidity, uidnext);

cleanup:
Expand Down Expand Up @@ -4409,7 +4481,7 @@ static int imap_process(struct imap_session *imap, char *s)
}
} else if (!strcasecmp(command, "APPEND")) {
REQUIRE_ARGS(s);
res = handle_append(imap, s);
res = handle_append(imap, s); /* Both local and remote */
} else if (allow_idle && !strcasecmp(command, "IDLE")) {
return handle_idle(imap); /* No need to check for updates right after an IDLE */
} else if (!strcasecmp(command, "NOTIFY")) {
Expand Down

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