https://bugs.gentoo.org/948106

Backport provided by Red Hat on the VINCE case.
diff --git a/io.c b/io.c
index a99ac0e..bb60eec 100644
--- a/io.c
+++ b/io.c
@@ -55,6 +55,7 @@ extern int read_batch;
 extern int compat_flags;
 extern int protect_args;
 extern int checksum_seed;
+extern int xfer_sum_len;
 extern int daemon_connection;
 extern int protocol_version;
 extern int remove_source_files;
@@ -1977,7 +1978,7 @@ void read_sum_head(int f, struct sum_struct *sum)
 		exit_cleanup(RERR_PROTOCOL);
 	}
 	sum->s2length = protocol_version < 27 ? csum_length : (int)read_int(f);
-	if (sum->s2length < 0 || sum->s2length > MAX_DIGEST_LEN) {
+	if (sum->s2length < 0 || sum->s2length > xfer_sum_len) {
 		rprintf(FERROR, "Invalid checksum length %d [%s]\n",
 			sum->s2length, who_am_i());
 		exit_cleanup(RERR_PROTOCOL);
diff --git a/match.c b/match.c
index cdb30a1..36e78ed 100644
--- a/match.c
+++ b/match.c
@@ -232,7 +232,7 @@ static void hash_search(int f,struct sum_struct *s,
 				done_csum2 = 1;
 			}
 
-			if (memcmp(sum2,s->sums[i].sum2,s->s2length) != 0) {
+			if (memcmp(sum2, sum2_at(s, i), s->s2length) != 0) {
 				false_alarms++;
 				continue;
 			}
@@ -252,7 +252,7 @@ static void hash_search(int f,struct sum_struct *s,
 					if (i != aligned_i) {
 						if (sum != s->sums[aligned_i].sum1
 						 || l != s->sums[aligned_i].len
-						 || memcmp(sum2, s->sums[aligned_i].sum2, s->s2length) != 0)
+						 || memcmp(sum2, sum2_at(s, aligned_i), s->s2length) != 0)
 							goto check_want_i;
 						i = aligned_i;
 					}
@@ -271,7 +271,7 @@ static void hash_search(int f,struct sum_struct *s,
 						if (sum != s->sums[i].sum1)
 							goto check_want_i;
 						get_checksum2((char *)map, l, sum2);
-						if (memcmp(sum2, s->sums[i].sum2, s->s2length) != 0)
+						if (memcmp(sum2, sum2_at(s, i), s->s2length) != 0)
 							goto check_want_i;
 						/* OK, we have a re-alignment match.  Bump the offset
 						 * forward to the new match point. */
@@ -290,7 +290,7 @@ static void hash_search(int f,struct sum_struct *s,
 			 && (!updating_basis_file || s->sums[want_i].offset >= offset
 			  || s->sums[want_i].flags & SUMFLG_SAME_OFFSET)
 			 && sum == s->sums[want_i].sum1
-			 && memcmp(sum2, s->sums[want_i].sum2, s->s2length) == 0) {
+			 && memcmp(sum2, sum2_at(s, want_i), s->s2length) == 0) {
 				/* we've found an adjacent match - the RLL coder
 				 * will be happy */
 				i = want_i;
diff --git a/rsync.c b/rsync.c
index cd288f5..b130aba 100644
--- a/rsync.c
+++ b/rsync.c
@@ -437,7 +437,10 @@ int read_ndx_and_attrs(int f_in, int f_out, int *iflag_ptr, uchar *type_ptr, cha
   */
 void free_sums(struct sum_struct *s)
 {
-	if (s->sums) free(s->sums);
+	if (s->sums) {
+		free(s->sums);
+		free(s->sum2_array);
+	}
 	free(s);
 }
 
diff --git a/rsync.h b/rsync.h
index d3709fe..0f9e277 100644
--- a/rsync.h
+++ b/rsync.h
@@ -958,12 +958,12 @@ struct sum_buf {
 	uint32 sum1;	        /**< simple checksum */
 	int32 chain;		/**< next hash-table collision */
 	short flags;		/**< flag bits */
-	char sum2[SUM_LENGTH];	/**< checksum  */
 };
 
 struct sum_struct {
 	OFF_T flength;		/**< total file length */
 	struct sum_buf *sums;	/**< points to info for each chunk */
+	char *sum2_array;	/**< checksums of length xfer_sum_len */
 	int32 count;		/**< how many chunks */
 	int32 blength;		/**< block_length */
 	int32 remainder;	/**< flength % block_length */
@@ -982,6 +982,8 @@ struct map_struct {
 	int status;		/* first errno from read errors		*/
 };
 
+#define sum2_at(s, i)	((s)->sum2_array + ((size_t)(i) * xfer_sum_len))
+
 #define NAME_IS_FILE		(0)    /* filter name as a file */
 #define NAME_IS_DIR		(1<<0) /* filter name as a dir */
 #define NAME_IS_XATTR		(1<<2) /* filter name as an xattr */
diff --git a/sender.c b/sender.c
index 3d4f052..2bbff2f 100644
--- a/sender.c
+++ b/sender.c
@@ -31,6 +31,7 @@ extern int log_before_transfer;
 extern int stdout_format_has_i;
 extern int logfile_format_has_i;
 extern int want_xattr_optim;
+extern int xfer_sum_len;
 extern int csum_length;
 extern int append_mode;
 extern int copy_links;
@@ -94,10 +95,11 @@ static struct sum_struct *receive_sums(int f)
 		return(s);
 
 	s->sums = new_array(struct sum_buf, s->count);
+	s->sum2_array = new_array(char, (size_t)s->count * xfer_sum_len);
 
 	for (i = 0; i < s->count; i++) {
 		s->sums[i].sum1 = read_int(f);
-		read_buf(f, s->sums[i].sum2, s->s2length);
+		read_buf(f, sum2_at(s, i), s->s2length);
 
 		s->sums[i].offset = offset;
 		s->sums[i].flags = 0;