Fixes segfault occurrence in PEM_write()

Checks if header is NULL or not before calling strlen().

CLA: trivial

Fixes #18825

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Ben Kaduk <kaduk@mit.edu>
Reviewed-by: Paul Dale <pauli@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/18865)

(cherry picked from commit 205957405d08ef199e6ab654e333a627bbca9ccc)

diff --git a/crypto/pem/pem_lib.c b/crypto/pem/pem_lib.c
index 2de093595d0d2e45962a78adf23ece83ee188f1d..c2cf407931d21308baee3b743522b70a75228319 100644 (file)
--- a/crypto/pem/pem_lib.c
+++ b/crypto/pem/pem_lib.c
@@ -621,7 +621,7 @@ int PEM_write_bio(BIO *bp, const char *name, const char *header,
         (BIO_write(bp, "-----\n", 6) != 6))
         goto err;
 
-    i = strlen(header);
+    i = header != NULL ? strlen(header) : 0;
     if (i > 0) {
         if ((BIO_write(bp, header, i) != i) || (BIO_write(bp, "\n", 1) != 1))
             goto err;