[patch] Fix for returning NULL values in SQL dict lookups

[NederHost/Sebastiaan Hoogeveen]

Hi,

I noticed a bug doing dict lookups on an SQLite database which had NULL values in its columns; a segmentation fault occurred, probably due to a null pointer dereference in str_tabescape. The problem is that sqlite3_column_text returns a null pointer for column values which are (SQL) NULL. It seems the other database drivers do something similar. The following patch makes the dict server check for null pointers and return a 'not found' reply in those cases (I changed the order around in the decision tree to avoid having to repeat return values):

diff -Naur dovecot-2.2.24/src/dict/dict-commands.c dovecot-2.2.24-patched/src/dict/dict-commands.c
--- dovecot-2.2.24/src/dict/dict-commands.c     2016-04-26 15:01:20.000000000 +0200
+++ dovecot-2.2.24-patched/src/dict/dict-commands.c     2016-05-11 22:04:06.000000000 +0200
@@ -83,14 +83,14 @@
 {
        struct dict_connection_cmd *cmd = context;
 
-       if (result->ret > 0) {
+       if (result->ret > 0 && result->value) {
                cmd->reply = i_strdup_printf("%c%s\n",
                        DICT_PROTOCOL_REPLY_OK, str_tabescape(result->value));
-       } else if (result->ret == 0) {
-               cmd->reply = i_strdup_printf("%c\n", DICT_PROTOCOL_REPLY_NOTFOUND);
-       } else {
+       } else if (result->ret < 0) {
                i_error("%s", result->error);
                cmd->reply = i_strdup_printf("%c\n", DICT_PROTOCOL_REPLY_FAIL);
+       } else {
+               cmd->reply = i_strdup_printf("%c\n", DICT_PROTOCOL_REPLY_NOTFOUND);
        }
        dict_connection_cmds_flush(cmd->conn);
 }


Kind regards,

-- 
Sebastiaan Hoogeveen

NederHost
https://www.nederhost.nl/
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