Revert "Give BIO_s_mem() the ability to support datagrams"

This reverts commit 5a4ba72f00f9b336a4d65abff822699ceb9617c6.

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Hugo Landau <hlandau@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/20012)

crypto/bio/bss_mem.c

@@ -18,7 +18,6 @@ static int mem_puts(BIO *h, const char *str);
 static int mem_gets(BIO *h, char *str, int size);
 static long mem_ctrl(BIO *h, int cmd, long arg1, void *arg2);
 static int mem_new(BIO *h);
-static int dgram_mem_new(BIO *h);
 static int secmem_new(BIO *h);
 static int mem_free(BIO *data);
 static int mem_buf_free(BIO *data);
@@ -39,21 +38,6 @@ static const BIO_METHOD mem_method = {
     NULL,                      /* mem_callback_ctrl */
 };
 
-static const BIO_METHOD dgram_mem_method = {
-    BIO_TYPE_MEM,
-    "datagram memory buffer",
-    bwrite_conv,
-    mem_write,
-    bread_conv,
-    mem_read,
-    mem_puts,
-    mem_gets,
-    mem_ctrl,
-    dgram_mem_new,
-    mem_free,
-    NULL,                      /* mem_callback_ctrl */
-};
-
 static const BIO_METHOD secmem_method = {
     BIO_TYPE_MEM,
     "secure memory buffer",
@@ -69,12 +53,6 @@ static const BIO_METHOD secmem_method = {
     NULL,                      /* mem_callback_ctrl */
 };
 
-struct buf_mem_dgram_st {
-    char *dgram;  /* Pointer into the buffer for where the dgram starts */
-    size_t dgramlen;  /* Length of the dgram */
-    struct buf_mem_dgram_st *next; /* Next dgram to read */
-};
-
 /*
  * BIO memory stores buffer and read pointer
  * however the roles are different for read only BIOs.
@@ -84,9 +62,6 @@ struct buf_mem_dgram_st {
 typedef struct bio_buf_mem_st {
     struct buf_mem_st *buf;   /* allocated buffer */
     struct buf_mem_st *readp; /* read pointer */
-    struct buf_mem_dgram_st *dgrams; /* linked list of dgram data */
-    struct buf_mem_dgram_st *last; /* last dgram in the linked list */
-    int use_dgrams;
 } BIO_BUF_MEM;
 
 /*
@@ -99,11 +74,6 @@ const BIO_METHOD *BIO_s_mem(void)
     return &mem_method;
 }
 
-const BIO_METHOD *BIO_s_dgram_mem(void)
-{
-    return &dgram_mem_method;
-}
-
 const BIO_METHOD *BIO_s_secmem(void)
 {
     return(&secmem_method);
@@ -164,39 +134,11 @@ static int mem_new(BIO *bi)
     return mem_init(bi, 0L);
 }
 
-static int dgram_mem_new(BIO *bi)
-{
-    BIO_BUF_MEM *bbm;
-
-    if (!mem_init(bi, 0L))
-        return 0;
-
-    bbm = (BIO_BUF_MEM *)bi->ptr;
-
-    bbm->use_dgrams = 1;
-    bi->num = -1;
-
-    return 1;
-}
-
 static int secmem_new(BIO *bi)
 {
     return mem_init(bi, BUF_MEM_FLAG_SECURE);
 }
 
-static void clear_all_dgrams(BIO_BUF_MEM *bbm)
-{
-    struct buf_mem_dgram_st *dgrams = bbm->dgrams;
-
-    while (dgrams != NULL) {
-        struct buf_mem_dgram_st *tmp = dgrams;
-
-        dgrams = dgrams->next;
-        OPENSSL_free(tmp);
-    }
-    bbm->dgrams = NULL;
-}
-
 static int mem_free(BIO *a)
 {
     BIO_BUF_MEM *bb;
@@ -208,7 +150,6 @@ static int mem_free(BIO *a)
     if (!mem_buf_free(a))
         return 0;
     OPENSSL_free(bb->readp);
-    clear_all_dgrams(bb);
     OPENSSL_free(bb);
     return 1;
 }
@@ -252,43 +193,17 @@ static int mem_read(BIO *b, char *out, int outl)
     int ret = -1;
     BIO_BUF_MEM *bbm = (BIO_BUF_MEM *)b->ptr;
     BUF_MEM *bm = bbm->readp;
-    size_t maxreadlen = 0;
-    int eof = 0;
 
     if (b->flags & BIO_FLAGS_MEM_RDONLY)
         bm = bbm->buf;
     BIO_clear_retry_flags(b);
-    if (bbm->use_dgrams) {
-        if (bbm->dgrams != NULL) {
-            maxreadlen = bbm->dgrams->dgramlen;
-            if (!ossl_assert(maxreadlen <= bm->length))
-                return 0;
-        } else {
-            eof = 1;
-        }
-    } else {
-        maxreadlen = bm->length;
-        eof = (maxreadlen == 0);
-    }
-    ret = (outl >= 0 && (size_t)outl > maxreadlen) ? (int)maxreadlen : outl;
+    ret = (outl >= 0 && (size_t)outl > bm->length) ? (int)bm->length : outl;
     if ((out != NULL) && (ret > 0)) {
-        size_t flushlen;
-
         memcpy(out, bm->data, ret);
-        flushlen = bbm->use_dgrams ? maxreadlen : (size_t)ret;
-            
-        bm->length -= flushlen;
-        bm->max -= flushlen;
-        bm->data += flushlen;
-        if (bbm->use_dgrams) {
-            struct buf_mem_dgram_st *tmp = bbm->dgrams;
-
-            bbm->dgrams = tmp->next;
-            OPENSSL_free(tmp);
-            if (bbm->dgrams == NULL)
-                bbm->last = NULL;
-        }
-    } else if (eof) {
+        bm->length -= ret;
+        bm->max -= ret;
+        bm->data += ret;
+    } else if (bm->length == 0) {
         ret = b->num;
         if (ret != 0)
             BIO_set_retry_read(b);
@@ -307,10 +222,8 @@ static int mem_write(BIO *b, const char *in, int inl)
         goto end;
     }
     BIO_clear_retry_flags(b);
-
     if (inl == 0)
         return 0;
-
     if (in == NULL) {
         ERR_raise(ERR_LIB_BIO, ERR_R_PASSED_NULL_PARAMETER);
         goto end;
@@ -319,26 +232,8 @@ static int mem_write(BIO *b, const char *in, int inl)
     mem_buf_sync(b);
     if (BUF_MEM_grow_clean(bbm->buf, blen + inl) == 0)
         goto end;
-
     memcpy(bbm->buf->data + blen, in, inl);
     *bbm->readp = *bbm->buf;
-
-    if (bbm->use_dgrams) {
-        struct buf_mem_dgram_st *dgram = OPENSSL_malloc(sizeof(*dgram));
-
-        if (dgram == NULL)
-            goto end;
-
-        dgram->dgram = bbm->buf->data + blen;
-        dgram->dgramlen = inl;
-        dgram->next = NULL;
-        if (bbm->dgrams == NULL)
-            bbm->dgrams = dgram;
-        else
-            bbm->last->next = dgram;
-        bbm->last = dgram;
-    }
-
     ret = inl;
  end:
     return ret;
@@ -377,7 +272,6 @@ static long mem_ctrl(BIO *b, int cmd, long num, void *ptr)
                 *bbm->buf = *bbm->readp;
             }
         }
-        clear_all_dgrams(bbm);
         break;
     case BIO_C_FILE_SEEK:
         if (num < 0 || num > off + remain)
@@ -392,13 +286,10 @@ static long mem_ctrl(BIO *b, int cmd, long num, void *ptr)
         ret = off;
         break;
     case BIO_CTRL_EOF:
-        ret = (long)(bm->length == 0 && bbm->use_dgrams == 0);
+        ret = (long)(bm->length == 0);
         break;
     case BIO_C_SET_BUF_MEM_EOF_RETURN:
-        if (!bbm->use_dgrams)
-            b->num = (int)num;
-        else
-            ret = -1;
+        b->num = (int)num;
         break;
     case BIO_CTRL_INFO:
         ret = (long)bm->length;
@@ -458,8 +349,7 @@ static int mem_gets(BIO *bp, char *buf, int size)
     if (bp->flags & BIO_FLAGS_MEM_RDONLY)
         bm = bbm->buf;
     BIO_clear_retry_flags(bp);
-    j = (!bbm->use_dgrams || bbm->dgrams == NULL) ? bm->length
-                                                  : bbm->dgrams->dgramlen;
+    j = bm->length;
     if ((size - 1) < j)
         j = size - 1;
     if (j <= 0) {