asn_mime: Harden strip_eol()

Signed-off-by: Joshua Rogers <MegaManSec@users.noreply.github.com>
Reviewed-by: Saša Nedvědický <sashan@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/28881)

diff --git a/crypto/asn1/asn_mime.c b/crypto/asn1/asn_mime.c
index c2aceffc1cf7b05ed02ed0b44778af3aadcf7fb7..c9bdfd98c848f24f56cfee81c3ac4fde31af676e 100644 (file)
--- a/crypto/asn1/asn_mime.c
+++ b/crypto/asn1/asn_mime.c
@@ -1048,6 +1048,11 @@ static int strip_eol(char *linebuf, int *plen, int flags)
     char *p, c;
     int is_eol = 0;
 
+    if (len <= 0) {
+        *plen = 0;
+        return 0;
+    }
+
 #ifndef OPENSSL_NO_CMS
     if ((flags & CMS_BINARY) != 0) {
         if (len <= 0 || linebuf[len - 1] != '\n')