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BUILD: ssl: work around bogus warning in gcc 12's -Wformat-truncation

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As was first reported by Ilya in issue #1513, Gcc 12 incorrectly reports
a possible overflow from the concatenation of two strings whose size was
previously checked to fit:

  src/ssl_crtlist.c: In function 'crtlist_parse_file':
  src/ssl_crtlist.c:545:58: error: '%s' directive output may be truncated writing up to 4095 bytes into a region of size between 1 and 4096 [-Werror=format-truncation=]
    545 |                         snprintf(path, sizeof(path), "%s/%s",  global_ssl.crt_base, crt_path);
        |                                                          ^~
  src/ssl_crtlist.c:545:25: note: 'snprintf' output between 2 and 8192 bytes into a destination of size 4097
    545 |                         snprintf(path, sizeof(path), "%s/%s",  global_ssl.crt_base, crt_path);
        |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

It would be a bit concerning to disable -Wformat-truncation because it
might detect real programming mistakes at other places. The solution
adopted in this patch is absolutely ugly and error-prone, but it works,
it consists in integrating the snprintf() call in the error condition
and to test the result again. Let's hope a smarter compiler will not
warn that this test is absurd since guaranteed by the first condition...

This may have to be backported for those suffering from a compiler upgrade.
This commit is contained in:
Willy Tarreau 2022-05-09 10:31:28 +02:00
parent ecab71fbac
commit 393e42ae5f
2 changed files with 6 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
src/cfgparse-ssl.c
View File

@ -659,11 +659,11 @@ static int bind_parse_crt(char **args, int cur_arg, struct proxy *px, struct bin
}
if ((*args[cur_arg + 1] != '/' ) && global_ssl.crt_base) {
if ((strlen(global_ssl.crt_base) + 1 + strlen(args[cur_arg + 1]) + 1) > MAXPATHLEN) {
if ((strlen(global_ssl.crt_base) + 1 + strlen(args[cur_arg + 1]) + 1) > sizeof(path) ||
snprintf(path, sizeof(path), "%s/%s", global_ssl.crt_base, args[cur_arg + 1]) > sizeof(path)) {
memprintf(err, "'%s' : path too long", args[cur_arg]);
return ERR_ALERT | ERR_FATAL;
}
snprintf(path, sizeof(path), "%s/%s", global_ssl.crt_base, args[cur_arg + 1]);
return ssl_sock_load_cert(path, conf, err);
}

8
src/ssl_crtlist.c
View File

@ -536,13 +536,13 @@ int crtlist_parse_file(char *file, struct bind_conf *bind_conf, struct proxy *cu
}
if (*crt_path != '/' && global_ssl.crt_base) {
if ((strlen(global_ssl.crt_base) + 1 + strlen(crt_path)) > MAXPATHLEN) {
if ((strlen(global_ssl.crt_base) + 1 + strlen(crt_path)) > sizeof(path) ||
snprintf(path, sizeof(path), "%s/%s", global_ssl.crt_base, crt_path)) {
memprintf(err, "parsing [%s:%d]: '%s' : path too long",
file, linenum, crt_path);
cfgerr |= ERR_ALERT | ERR_FATAL;
goto error;
}
snprintf(path, sizeof(path), "%s/%s", global_ssl.crt_base, crt_path);
crt_path = path;
}
@ -1270,12 +1270,12 @@ static int cli_parse_add_crtlist(char **args, char *payload, struct appctx *appc
}
if (*cert_path != '/' && global_ssl.crt_base) {
if ((strlen(global_ssl.crt_base) + 1 + strlen(cert_path)) > MAXPATHLEN) {
if ((strlen(global_ssl.crt_base) + 1 + strlen(cert_path)) > sizeof(path) ||
snprintf(path, sizeof(path), "%s/%s", global_ssl.crt_base, cert_path) > sizeof(path)) {
memprintf(&err, "'%s' : path too long", cert_path);
cfgerr |= ERR_ALERT | ERR_FATAL;
goto error;
}
snprintf(path, sizeof(path), "%s/%s", global_ssl.crt_base, cert_path);
cert_path = path;
}