Remove undesirable libpq dependency on stringinfo.c.

tglsfdc · tglsfdc · commit 8ec00dc5cd70 · 2021-06-26T14:20:17.000-04:00
Commit c0cb87f unwisely introduced a dependency on the StringInfo machinery in fe-connect.c. We must not use that in libpq, because it will do a summary exit(1) if it hits OOM, and that is not appropriate behavior for a general-purpose library. The goal of allowing arbitrary line lengths in service files doesn't seem like it's worth a lot of effort, so revert back to the previous method of using a stack-allocated buffer and failing on buffer overflow. This isn't an exact revert though. I kept that patch's refactoring to have a single exit path, as that seems cleaner than having each error path know what to do to clean up. Also, I made the fixed-size buffer 1024 bytes not 256, just to push off the need for an expandable buffer some more. There is more to do here; in particular the lack of any mechanical check for this type of mistake now seems pretty hazardous. But this fix gets us back to the level of robustness we had in v13, anyway. Discussion: https://postgr.es/m/daeb22ec6ca8ef61e94d766a9b35fb03cabed38e.camel@vmware.com
diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
@@ -28,7 +28,6 @@
 #include "fe-auth.h"
 #include "libpq-fe.h"
 #include "libpq-int.h"
-#include "lib/stringinfo.h"
 #include "mb/pg_wchar.h"
 #include "pg_config_paths.h"
 #include "port/pg_bswap.h"
@@ -5163,7 +5162,7 @@ parseServiceFile(const char *serviceFile,
 				i;
 	FILE	   *f;
 	char	   *line;
-	StringInfoData linebuf;
+	char		buf[1024];
 
 	*group_found = false;
 
@@ -5175,18 +5174,26 @@ parseServiceFile(const char *serviceFile,
 		return 1;
 	}
 
-	initStringInfo(&linebuf);
-
-	while (pg_get_line_buf(f, &linebuf))
+	while ((line = fgets(buf, sizeof(buf), f)) != NULL)
 	{
+		int			len;
+
 		linenr++;
 
-		/* ignore whitespace at end of line, especially the newline */
-		while (linebuf.len > 0 &&
-			   isspace((unsigned char) linebuf.data[linebuf.len - 1]))
-			linebuf.data[--linebuf.len] = '\0';
+		if (strlen(line) >= sizeof(buf) - 1)
+		{
+			appendPQExpBuffer(errorMessage,
+							  libpq_gettext("line %d too long in service file \"%s\"\n"),
+							  linenr,
+							  serviceFile);
+			result = 2;
+			goto exit;
+		}
 
-		line = linebuf.data;
+		/* ignore whitespace at end of line, especially the newline */
+		len = strlen(line);
+		while (len > 0 && isspace((unsigned char) line[len - 1]))
+			line[--len] = '\0';
 
 		/* ignore leading whitespace too */
 		while (*line && isspace((unsigned char) line[0]))
@@ -5303,7 +5310,6 @@ parseServiceFile(const char *serviceFile,
 
 exit:
 	fclose(f);
-	pfree(linebuf.data);
 
 	return result;
 }
