Avoid integer overflows in SETRANGE and SORT (CVE-2022-35977)

Authenticated users issuing specially crafted SETRANGE and SORT(_RO)
commands can trigger an integer overflow, resulting with Redis attempting
to allocate impossible amounts of memory and abort with an OOM panic.

src/server.h

@@ -83,6 +83,12 @@ typedef long long ustime_t; /* microsecond time type. */
 #include "endianconv.h"
 #include "crc64.h"
 
+/* min/max */
+#undef min
+#undef max
+#define min(a, b) ((a) < (b) ? (a) : (b))
+#define max(a, b) ((a) > (b) ? (a) : (b))
+
 /* Error codes */
 #define C_OK                    0
 #define C_ERR                   -1

src/sort.c

@@ -320,8 +320,10 @@ void sortCommand(client *c) {
     default: vectorlen = 0; serverPanic("Bad SORT type"); /* Avoid GCC warning */
     }
 
-    /* Perform LIMIT start,count sanity checking. */
+    /* Perform LIMIT start,count sanity checking.
-    start = (limit_start < 0) ? 0 : limit_start;
+     * And avoid integer overflow by limiting inputs to object sizes. */
+    start = min(max(limit_start, 0), vectorlen);
+    limit_count = min(max(limit_count, -1), vectorlen);
     end = (limit_count < 0) ? vectorlen-1 : start+limit_count-1;
     if (start >= vectorlen) {
         start = vectorlen-1;

src/t_string.c

@@ -34,8 +34,14 @@
  * String Commands
  *----------------------------------------------------------------------------*/
 
-static int checkStringLength(client *c, long long size) {
+static int checkStringLength(client *c, long long size, long long append) {
-    if (!(c->flags & CLIENT_MASTER) && size > server.proto_max_bulk_len) {
+    if (c->flags & CLIENT_MASTER)
+        return C_OK;
+    /* 'uint64_t' cast is there just to prevent undefined behavior on overflow */
+    long long total = (uint64_t)size + append;
+    /* Test configured max-bulk-len represending a limit of the biggest string object,
+     * and also test for overflow. */
+    if (total > server.proto_max_bulk_len || total < size || total < append) {
         addReplyError(c,"string exceeds maximum allowed size (proto-max-bulk-len)");
         return C_ERR;
     }
@@ -210,7 +216,7 @@ void setrangeCommand(client *c) {
         }
 
         /* Return when the resulting string exceeds allowed size */
-        if (checkStringLength(c,offset+sdslen(value)) != C_OK)
+        if (checkStringLength(c,offset,sdslen(value)) != C_OK)
             return;
 
         o = createObject(OBJ_STRING,sdsnewlen(NULL, offset+sdslen(value)));
@@ -230,7 +236,7 @@ void setrangeCommand(client *c) {
         }
 
         /* Return when the resulting string exceeds allowed size */
-        if (checkStringLength(c,offset+sdslen(value)) != C_OK)
+        if (checkStringLength(c,offset,sdslen(value)) != C_OK)
             return;
 
         /* Create a copy when the object is shared or encoded. */
@@ -458,8 +464,7 @@ void appendCommand(client *c) {
 
         /* "append" is an argument, so always an sds */
         append = c->argv[2];
-        totlen = stringObjectLen(o)+sdslen(append->ptr);
+        if (checkStringLength(c,stringObjectLen(o),sdslen(append->ptr)) != C_OK)
-        if (checkStringLength(c,totlen) != C_OK)
             return;
 
         /* Append the value */

tests/support/test.tcl

@@ -31,6 +31,12 @@ proc assert_match {pattern value} {
     }
 }
 
+proc assert_not_equal {value expected {detail ""}} {
+    if {!($expected ne $value)} {
+        assert_failed "Expected '$value' not equal to '$expected'" $detail
+    }
+}
+
 proc assert_equal {value expected {detail ""}} {
     if {$expected ne $value} {
         if {$detail ne ""} {

tests/unit/sort.tcl

@@ -315,4 +315,15 @@ start_server {
             }
         }
     }
+
+    test {SETRANGE with huge offset} {
+        r lpush L 2 1 0
+        # expecting a different outcome on 32 and 64 bit systems
+        foreach value {9223372036854775807 2147483647} {
+            catch {[r sort_ro L by a limit 2 $value]} res
+            if {![string match "2" $res] && ![string match "*out of range*" $res]} {
+                assert_not_equal $res "expecting an error or 2"
+            }
+        }
+    }
 }

tests/unit/type/string.tcl

@@ -449,4 +449,14 @@ start_server {tags {"string"}} {
     test {LCS indexes with match len and minimum match len} {
         dict get [r STRALGO LCS IDX KEYS virus1 virus2 WITHMATCHLEN MINMATCHLEN 5] matches
     } {{{1 222} {13 234} 222}}
+
+    test {SETRANGE with huge offset} {
+        foreach value {9223372036854775807 2147483647} {
+            catch {[r setrange K $value A]} res
+            # expecting a different error on 32 and 64 bit systems
+            if {![string match "*string exceeds maximum allowed size*" $res] && ![string match "*out of range*" $res]} {
+                assert_equal $res "expecting an error"
+           }
+        }
+    }
 }