Eliminate fixed token-length limit in hba.c.

Historically, hba.c limited tokens in the authentication configuration
files (pg_hba.conf and pg_ident.conf) to less than 256 bytes.  We have
seen a few reports of this limit causing problems; notably, for
moderately-complex LDAP configurations.  Let's get rid of the fixed
limit by using a StringInfo instead of a fixed-size buffer.
This actually takes less code than before, since we can get rid of
a nontrivial error recovery stanza.  It's doubtless a hair slower,
but parsing the content of the HBA files should in no way be
performance-critical.

Although this is a pretty straightforward patch, it doesn't seem
worth the risk to back-patch given the small number of complaints
to date.  In released branches, we'll just raise MAX_TOKEN to
ameliorate the problem.

Discussion: https://postgr.es/m/1588937.1690221208@sss.pgh.pa.us

diff --git a/src/backend/libpq/hba.c b/src/backend/libpq/hba.c
index f89f138f3c01e56c4c9e4870cddfa13fc118f3f5..75fd2a88939bb18881782b826f34d5c2ee646744 100644 (file)
--- a/src/backend/libpq/hba.c
+++ b/src/backend/libpq/hba.c
@@ -56,8 +56,6 @@
 #endif
 
 
-#define MAX_TOKEN      256
-
 /* callback data for check_network_callback */
 typedef struct check_network_data
 {
@@ -161,8 +159,8 @@ pg_isblank(const char c)
  * commas, beginning of line, and end of line.  Blank means space or tab.
  *
  * Tokens can be delimited by double quotes (this allows the inclusion of
- * blanks or '#', but not newlines).  As in SQL, write two double-quotes
- * to represent a double quote.
+ * commas, blanks, and '#', but not newlines).  As in SQL, write two
+ * double-quotes to represent a double quote.
  *
  * Comments (started by an unquoted '#') are skipped, i.e. the remainder
  * of the line is ignored.
@@ -171,8 +169,8 @@ pg_isblank(const char c)
  * Thus, if a continuation occurs within quoted text or a comment, the
  * quoted text or comment is considered to continue to the next line.)
  *
- * The token, if any, is returned at *buf (a buffer of size bufsz), and
- * *lineptr is advanced past the token.
+ * The token, if any, is returned into buf (replacing any previous
+ * contents), and *lineptr is advanced past the token.
  *
  * Also, we set *initial_quote to indicate whether there was quoting before
  * the first character.  (We use that to prevent "@x" from being treated
@@ -180,30 +178,25 @@ pg_isblank(const char c)
  * we want to allow that to support embedded spaces in file paths.)
  *
  * We set *terminating_comma to indicate whether the token is terminated by a
- * comma (which is not returned).
+ * comma (which is not returned, nor advanced over).
  *
- * In event of an error, log a message at ereport level elevel, and also
- * set *err_msg to a string describing the error.  Currently the only
- * possible error is token too long for buf.
+ * The only possible error condition is lack of terminating quote, but we
+ * currently do not detect that, but just return the rest of the line.
  *
- * If successful: store null-terminated token at *buf and return true.
- * If no more tokens on line: set *buf = '\0' and return false.
- * If error: fill buf with truncated or misformatted token and return false.
+ * If successful: store dequoted token in buf and return true.
+ * If no more tokens on line: set buf to empty and return false.
  */
 static bool
-next_token(char **lineptr, char *buf, int bufsz,
-                  bool *initial_quote, bool *terminating_comma,
-                  int elevel, char **err_msg)
+next_token(char **lineptr, StringInfo buf,
+                  bool *initial_quote, bool *terminating_comma)
 {
        int                     c;
-       char       *start_buf = buf;
-       char       *end_buf = buf + (bufsz - 1);
        bool            in_quote = false;
        bool            was_quote = false;
        bool            saw_quote = false;
 
-       Assert(end_buf > start_buf);
-
+       /* Initialize output parameters */
+       resetStringInfo(buf);
        *initial_quote = false;
        *terminating_comma = false;
 
@@ -226,22 +219,6 @@ next_token(char **lineptr, char *buf, int bufsz,
                        break;
                }
 
-               if (buf >= end_buf)
-               {
-                       *buf = '\0';
-                       ereport(elevel,
-                                       (errcode(ERRCODE_CONFIG_FILE_ERROR),
-                                        errmsg("authentication file token too long, skipping: \"%s\"",
-                                                       start_buf)));
-                       *err_msg = "authentication file token too long";
-                       /* Discard remainder of line */
-                       while ((c = (*(*lineptr)++)) != '\0')
-                               ;
-                       /* Un-eat the '\0', in case we're called again */
-                       (*lineptr)--;
-                       return false;
-               }
-
                /* we do not pass back a terminating comma in the token */
                if (c == ',' && !in_quote)
                {
@@ -250,7 +227,7 @@ next_token(char **lineptr, char *buf, int bufsz,
                }
 
                if (c != '"' || was_quote)
-                       *buf++ = c;
+                       appendStringInfoChar(buf, c);
 
                /* Literal double-quote is two double-quotes */
                if (in_quote && c == '"')
@@ -262,7 +239,7 @@ next_token(char **lineptr, char *buf, int bufsz,
                {
                        in_quote = !in_quote;
                        saw_quote = true;
-                       if (buf == start_buf)
+                       if (buf->len == 0)
                                *initial_quote = true;
                }
 
@@ -275,9 +252,7 @@ next_token(char **lineptr, char *buf, int bufsz,
         */
        (*lineptr)--;
 
-       *buf = '\0';
-
-       return (saw_quote || buf > start_buf);
+       return (saw_quote || buf->len > 0);
 }
 
 /*
@@ -409,21 +384,22 @@ static List *
 next_field_expand(const char *filename, char **lineptr,
                                  int elevel, int depth, char **err_msg)
 {
-       char            buf[MAX_TOKEN];
+       StringInfoData buf;
        bool            trailing_comma;
        bool            initial_quote;
        List       *tokens = NIL;
 
+       initStringInfo(&buf);
+
        do
        {
-               if (!next_token(lineptr, buf, sizeof(buf),
-                                               &initial_quote, &trailing_comma,
-                                               elevel, err_msg))
+               if (!next_token(lineptr, &buf,
+                                               &initial_quote, &trailing_comma))
                        break;
 
                /* Is this referencing a file? */
-               if (!initial_quote && buf[0] == '@' && buf[1] != '\0')
-                       tokens = tokenize_expand_file(tokens, filename, buf + 1,
+               if (!initial_quote && buf.len > 1 && buf.data[0] == '@')
+                       tokens = tokenize_expand_file(tokens, filename, buf.data + 1,
                                                                                  elevel, depth + 1, err_msg);
                else
                {
@@ -434,11 +410,13 @@ next_field_expand(const char *filename, char **lineptr,
                         * for the list of tokens.
                         */
                        oldcxt = MemoryContextSwitchTo(tokenize_context);
-                       tokens = lappend(tokens, make_auth_token(buf, initial_quote));
+                       tokens = lappend(tokens, make_auth_token(buf.data, initial_quote));
                        MemoryContextSwitchTo(oldcxt);
                }
        } while (trailing_comma && (*err_msg == NULL));
 
+       pfree(buf.data);
+
        return tokens;
 }