feat(commands/hexdump): Add configurable size limit (#2803)

* feat(commands/hexdump): Add configurable size limit check

* feat(commands/hexdump): Add configurable size limit check

* test(commands/hexdump): Add tests for hexdump size limit

pwndbg/commands/hexdump.py

@@ -10,6 +10,7 @@ import pwndbg.commands
 import pwndbg.hexdump
 from pwndbg.color import message
 from pwndbg.commands import CommandCategory
+from pwndbg.lib.config import PARAM_ZUINTEGER
 
 pwndbg.config.add_param("hexdump-width", 16, "line width of hexdump command")
 pwndbg.config.add_param("hexdump-bytes", 64, "number of bytes printed by hexdump command")
@@ -25,6 +26,16 @@ pwndbg.config.add_param(
     help_docstring="When `on`, use big-endian within each group of bytes. Only applies to raw bytes, not the ASCII part. "
     "See also hexdump-highlight-group-lsb.",
 )
+pwndbg.config.add_param(
+    "hexdump-limit-mb",
+    10,
+    "the maximum size in megabytes (MB) `hexdump` will read",
+    help_docstring="""Set the maximum size in megabytes (MB) that the `hexdump` command will attempt to read at once.
+    Prevents GDB crashes due to excessive memory allocation requests.
+    Set to 0 for unlimited (use with caution).""",
+    param_class=PARAM_ZUINTEGER,
+    scope="memory",
+)
 
 
 def address_or_module_name(s) -> int:
@@ -76,6 +87,20 @@ def hexdump(address, count=pwndbg.config.hexdump_bytes) -> None:
         address = new_address
 
     count = max(int(count), 0)
+
+    # Get the configured limit in MB
+    limit_mb = int(pwndbg.config.hexdump_limit_mb)
+
+    # Check if the limit is enabled (non-zero) and if the request count exceeds it
+    if limit_mb > 0:
+        limit_bytes = limit_mb * 1024 * 1024
+        if count > limit_bytes:
+            # Raise an error with the informative message
+            raise ValueError(
+                f"Hexdump count ({count}) exceeds the current limit of {limit_mb} MB.\n"
+                f"Use 'set hexdump-limit-mb <new_limit_in_mb>' to increase the limit (or set to 0 for unlimited)."
+            )
+
     width = int(pwndbg.config.hexdump_width)
 
     group_width = int(pwndbg.config.hexdump_group_width)

tests/gdb-tests/tests/test_hexdump.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import gdb
+import pytest
 from pwnlib.util.cyclic import cyclic
 
 import pwndbg
@@ -103,3 +104,56 @@ def test_hexdump_saved_address_and_offset(start_binary):
     assert out1 == out2
     assert pwndbg.commands.hexdump.hexdump.last_address == sp + SIZE
     assert pwndbg.commands.hexdump.hexdump.offset == SIZE
+
+
+def test_hexdump_limit_check(start_binary):
+    """
+    Tests that the hexdump command respects the hexdump-limit-mb settings.
+    """
+    start_binary(BINARY)
+    sp = pwndbg.aglib.regs.rsp
+
+    # Default limit is 10 MB
+    default_limit_mb = 10
+    limit_bytes = default_limit_mb * 1024 * 1024
+    count_over_limit = limit_bytes + 1
+    count_within_limit = limit_bytes // 2  # Using a value clearly within the limit
+
+    # 1. Test that count over the default limit raises PwndbgError
+    print(f"Testing count over default limit ({count_over_limit} bytes)")
+    with pytest.raises(gdb.error, match="exceeds the current limit"):
+        gdb.execute(f"hexdump {sp} {count_over_limit}", to_string=True)
+    print(" -> Correctly raised error.")
+
+    # 2. Test that count within the default limit works
+    print(f"Testing count within default limit ({count_within_limit} bytes)")
+    # We don't expect an error here. Just executing it is the test.
+    # We could assert on the output, but simply not crashing/erroring is the main goal.
+    try:
+        gdb.execute(f"hexdump {sp} {count_within_limit}", to_string=True)
+    except Exception as e:
+        pytest.fail(f"Hexdump failed unexpectedly with count within limit: {e}")
+    print(" -> Correctly executed.")
+
+    # 3. Test increasing the limit allows larger dumps
+    new_limit_mb = 15
+    count_over_default_under_new = (default_limit_mb + 1) * 1024 * 1024
+    print(f"Setting limit to {new_limit_mb} MB and testing count {count_over_default_under_new}")
+    gdb.execute(f"set hexdump-limit-mb {new_limit_mb}")
+    try:
+        gdb.execute(f"hexdump {sp} {count_over_default_under_new}", to_string=True)
+    except Exception as e:
+        pytest.fail(f"Hexdump failed unexpectedly after increasing limit: {e}")
+    print(" -> Correctly executed after increasing limit.")
+
+    # 4. Test disabling the limit (set to 0) allows larger dumps
+    print(f"Setting limit to 0 and testing count {count_over_default_under_new}")
+    gdb.execute("set hexdump-limit-mb 0")
+    try:
+        gdb.execute(f"hexdump {sp} {count_over_default_under_new}", to_string=True)
+    except Exception as e:
+        pytest.fail(f"Hexdump failed unexpectedly after disabling limit: {e}")
+    print(" -> Correctly executed after disabling limit.")
+
+    # Reset to default for subsequent tests if any
+    gdb.execute(f"set hexdump-limit-mb {default_limit_mb}")