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[71.206.142.238]) by smtp.gmail.com with ESMTPSA id f13-20020ac8134d000000b00410ac0068d0sm1167159qtj.91.2023.09.15.07.13.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 15 Sep 2023 07:13:05 -0700 (PDT) From: Joe Simmons-Talbott To: libc-alpha@sourceware.org Cc: Joe Simmons-Talbott Subject: [PATCH] crypt: Get rid of alloca usage in __md5_crypt_r Date: Fri, 15 Sep 2023 10:12:57 -0400 Message-ID: <20230915141302.2093730-1-josimmon@redhat.com> X-Mailer: git-send-email 2.41.0 MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com X-Spam-Status: No, score=-12.6 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H3, RCVD_IN_MSPIKE_WL, SPF_HELO_NONE, SPF_NONE, TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.30 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: libc-alpha-bounces+incoming=patchwork.ozlabs.org@sourceware.org Replace alloca usage with scratch_buffers to avoid potential stack overflow. --- crypt/md5-crypt.c | 35 +++++++++++++++++++++++------------ 1 file changed, 23 insertions(+), 12 deletions(-) diff --git a/crypt/md5-crypt.c b/crypt/md5-crypt.c index 4e4760545a..891bfedf88 100644 --- a/crypt/md5-crypt.c +++ b/crypt/md5-crypt.c @@ -19,6 +19,7 @@ #include #include +#include #include #include #include @@ -99,7 +100,10 @@ __md5_crypt_r (const char *key, const char *salt, char *buffer, int buflen) char *copied_key = NULL; char *copied_salt = NULL; char *free_key = NULL; - size_t alloca_used = 0; + struct scratch_buffer sbuf; + scratch_buffer_init (&sbuf); + struct scratch_buffer saltbuf; + scratch_buffer_init (&saltfuf); /* Find beginning of salt string. The prefix should normally always be present. Just in case it is not. */ @@ -114,14 +118,11 @@ __md5_crypt_r (const char *key, const char *salt, char *buffer, int buflen) { char *tmp; - if (__libc_use_alloca (alloca_used + key_len + __alignof__ (md5_uint32))) - tmp = (char *) alloca (key_len + __alignof__ (md5_uint32)); - else - { - free_key = tmp = (char *) malloc (key_len + __alignof__ (md5_uint32)); - if (tmp == NULL) - return NULL; - } + if (!scratch_buffer_set_array_size ( + &sbuf, 1, key_len + __alignof__ (md5_unint32)) + return NULL; + + tmp = sbuf.data; key = copied_key = memcpy (tmp + __alignof__ (md5_uint32) @@ -132,7 +133,15 @@ __md5_crypt_r (const char *key, const char *salt, char *buffer, int buflen) if (((uintptr_t) salt) % __alignof__ (md5_uint32) != 0) { - char *tmp = (char *) alloca (salt_len + __alignof__ (md5_uint32)); + if (!scratch_buffer_set_array_size ( + &saltbuf, salt_len * __alignof__ (md5_uint32))) + { + scratch_buffer_free (&sbuf); + return NULL; + } + + char *tmp = saltbuf.data; + salt = copied_salt = memcpy (tmp + __alignof__ (md5_uint32) - ((uintptr_t) tmp) % __alignof__ (md5_uint32), @@ -145,7 +154,8 @@ __md5_crypt_r (const char *key, const char *salt, char *buffer, int buflen) NSSLOWInitContext *nss_ictx = NSSLOW_Init (); if (nss_ictx == NULL) { - free (free_key); + scratch_buffer_free (&sbuf); + scratch_buffer_free (&saltbuf); return NULL; } NSSLOWHASHContext *nss_ctx = NULL; @@ -295,7 +305,8 @@ __md5_crypt_r (const char *key, const char *salt, char *buffer, int buflen) if (copied_salt != NULL) explicit_bzero (copied_salt, salt_len); - free (free_key); + scratch_buffer_free (&sbuf); + scratch_buffer_free (&saltbuf); return buffer; }