From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-qv1-f66.google.com (mail-qv1-f66.google.com [209.85.219.66]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AA5FA3112B3 for ; Fri, 16 Jan 2026 22:26:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.219.66 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768602384; cv=none; b=UPcFn/mJJEmCufby7wLk+oUVxyQ0r2DtW+R/BGXZbkH54IywQ8ReUt7enhA0r57xBRGOiLLQpJfCatKHrYb8vUCJc6DI+kjwa6VTHfirb4sdS59Jd64ory4IsM+UASDqP/xyBX9q1/BRhccVQwrWIK3Zh4n2Psuv5uE1NT0uf0M= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768602384; c=relaxed/simple; bh=i4hAx7jO6qMY2u2oFQunwlH2FEPU5FKviGB0WIQ9oDs=; h=Message-Id:In-Reply-To:References:From:Date:Subject:Content-Type: MIME-Version:To:Cc; b=nZnBR/pZaXHbSGWDtIdJyiW+7Luw4BHhbYXPIJW3rArrcmo37o1dldKHFplP2Sygd/epNw4ByA5VrgORqqabMfNYHFa3zgyGGcfTKaTNkH20s8zluhiZwGc221aVCWXwX+TU48ZYhU9u3K0ZKRrZZqhbkCKUFy+aKTozsqqAHvU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=AACc14An; arc=none smtp.client-ip=209.85.219.66 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="AACc14An" Received: by mail-qv1-f66.google.com with SMTP id 6a1803df08f44-88ffcb14e11so32450896d6.0 for ; Fri, 16 Jan 2026 14:26:22 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1768602381; x=1769207181; darn=vger.kernel.org; h=cc:to:mime-version:content-transfer-encoding:fcc:subject:date:from :references:in-reply-to:message-id:from:to:cc:subject:date :message-id:reply-to; bh=AU95jvPU4QC0PrPwv6HoETsmYVbMHAn2/lNUyKEaMmc=; b=AACc14An0B+z8eZQshp6X0F8lUCHDOvuiQI3M/5Dpd9YP+5+qHttlLa7AZp75BhsXY DGoTJM2f1j4se3Myy9D3bpqK2n8pkUjfQmvkYpVcHgllEzxZtFNRj0oGMq7/RUKKQHMI RW5R8AtgDzGtM5G8PPQUAJRC2h3o1U3pBwPgPUyuWonGqkrOPXUDxdu0e9seEp1EFTJR udB6+LBccGX3BPQmx8SFyQ9qbdEVY+ztcZipP8Y+NlQKkSw3ahf8swQKO2i9PDL0BhCg y2aHcx8sp7UoLmbQZ+5TGaq0uwS//R8FkqruOeoRl8hwWG+uR9BVG8OTB18gHwqBcjTD DIwQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1768602381; x=1769207181; h=cc:to:mime-version:content-transfer-encoding:fcc:subject:date:from :references:in-reply-to:message-id:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to; bh=AU95jvPU4QC0PrPwv6HoETsmYVbMHAn2/lNUyKEaMmc=; b=GWsZq6fG2QZ60oMbrX4j/A1mQM9p0kkw48MS6IrgOmhPZmT9IoQWUbNKZW1Jl5NBmQ rMap4yWgwMQVWHLbh7N9/WJt3a/n0JOZ8bUsmfW+vLdUT3C8hTBxAeusCDsaFgObUeHu /9LfdO070l8NIiigQ3wMRt4LAzFN18khibxQG7JYQflPVYMMMg+ixUjxE8bywuC6Xyun y1COo/JENpFQipMwrh/ZQ++07PhbBxCVbcL4k5tukhwNEspdNbjWbznfeJTbndtd3Pgt /3HDoQKHmen+zhKyLhkTnnnqkDyklplNstw2vtxBnXJmih5hzrwIOk+gL83Zc8Bzu1+7 G+zg== X-Gm-Message-State: AOJu0YzGi94Xg9XXT5GuPkIaUoj8SOqmFd3C7RysvOM35luaHnKXGcdc bc1pUKWAr6WNIOqQmUqgA8MWRnK4kj2qD8pzVWgLLaSigoTPE60dJtyU7vN3HiB2 X-Gm-Gg: AY/fxX56xqshALudQbHcIYObyzOxt8DfVh6oi3a96uHVo0xIcT0lRYd+th+oSt8Ro0u ZVYrDcdGYorGIqGjb6UVe7yatqa40wrDp7Z0yx0+TRf298E2W3lyPGeQk1Ceh+0+yg1fa7VhK2S IfXdA3/CiIE6A3hou6gQ34rMXSLrzFCcOridz4XWASaPZr4Wj+QfvV26cudsPqk6YDHnKXLm8a4 M76dAkuQPKmQpohddzinhS2ThVUcRhVkGLuz+pfVKVSdtKMoJc9x+2hpOdGzlFcA5DmtgdBT0EM +BxX9Mt0q1Y3np2MKB1+pZVnA/VTGbCnBX8r2UB1asbr6VuzFWWwII5ihvEVEro/D/095n65rMA qkinQqREglLxx0QkiIhK/UqF8ZplYq3yO78Bm1Ss5+CivS9bGad/DeLUTrM/VOIgE3bPcQAkrEy /alMwRT7RivQ6xZw== X-Received: by 2002:a05:622a:d5:b0:4ee:7ee:df70 with SMTP id d75a77b69052e-502a17af27amr66065881cf.80.1768602381169; Fri, 16 Jan 2026 14:26:21 -0800 (PST) Received: from [127.0.0.1] ([64.236.153.100]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-8942e6049d9sm32455986d6.23.2026.01.16.14.26.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 16 Jan 2026 14:26:20 -0800 (PST) Message-Id: In-Reply-To: References: From: "Johannes Schindelin via GitGitGadget" Date: Fri, 16 Jan 2026 22:26:12 +0000 Subject: [PATCH v3 4/5] sideband: add options to allow more control sequences to be passed through Fcc: Sent Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk X-Mailing-List: git@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 To: git@vger.kernel.org Cc: "brian m. carlson" , Phillip Wood , Andreas Schwab , Ondrej Pohorelsky , Patrick Steinhardt , Jeff King , Johannes Schindelin , Johannes Schindelin From: Johannes Schindelin Even though control sequences that erase characters are quite juicy for attack scenarios, where attackers are eager to hide traces of suspicious activities, during the review of the side band sanitizing patch series concerns were raised that there might be some legimitate scenarios where Git server's `pre-receive` hooks use those sequences in a benign way. Control sequences to move the cursor can likewise be used to hide tracks by overwriting characters, and have been equally pointed out as having legitimate users. Let's add options to let users opt into passing through those ANSI Escape sequences: `sideband.allowControlCharacters` now supports also `cursor` and `erase`, and it parses the value as a comma-separated list. Signed-off-by: Johannes Schindelin --- Documentation/config/sideband.txt | 9 ++- sideband.c | 91 ++++++++++++++++++++++++----- t/t5409-colorize-remote-messages.sh | 38 ++++++++++++ 3 files changed, 123 insertions(+), 15 deletions(-) diff --git a/Documentation/config/sideband.txt b/Documentation/config/sideband.txt index b55c73726f..2bf0426284 100644 --- a/Documentation/config/sideband.txt +++ b/Documentation/config/sideband.txt @@ -2,13 +2,20 @@ sideband.allowControlCharacters:: By default, control characters that are delivered via the sideband are masked, except ANSI color sequences. This prevents potentially unwanted ANSI escape sequences from being sent to the terminal. Use - this config setting to override this behavior: + this config setting to override this behavior (the value can be + a comma-separated list of the following keywords): + -- `default`:: `color`:: Allow ANSI color sequences, line feeds and horizontal tabs, but mask all other control characters. This is the default. + `cursor:`: + Allow control sequences that move the cursor. This is + disabled by default. + `erase`:: + Allow control sequences that erase charactrs. This is + disabled by default. `false`:: Mask all control characters other than line feeds and horizontal tabs. diff --git a/sideband.c b/sideband.c index f4bcdcaf9b..a8568b8b64 100644 --- a/sideband.c +++ b/sideband.c @@ -28,9 +28,43 @@ static struct keyword_entry keywords[] = { static enum { ALLOW_NO_CONTROL_CHARACTERS = 0, ALLOW_ANSI_COLOR_SEQUENCES = 1<<0, + ALLOW_ANSI_CURSOR_MOVEMENTS = 1<<1, + ALLOW_ANSI_ERASE = 1<<2, ALLOW_DEFAULT_ANSI_SEQUENCES = ALLOW_ANSI_COLOR_SEQUENCES, - ALLOW_ALL_CONTROL_CHARACTERS = 1<<1, -} allow_control_characters = ALLOW_ANSI_COLOR_SEQUENCES; + ALLOW_ALL_CONTROL_CHARACTERS = 1<<3, +} allow_control_characters = ALLOW_DEFAULT_ANSI_SEQUENCES; + +static inline int skip_prefix_in_csv(const char *value, const char *prefix, + const char **out) +{ + if (!skip_prefix(value, prefix, &value) || + (*value && *value != ',')) + return 0; + *out = value + !!*value; + return 1; +} + +static void parse_allow_control_characters(const char *value) +{ + allow_control_characters = ALLOW_NO_CONTROL_CHARACTERS; + while (*value) { + if (skip_prefix_in_csv(value, "default", &value)) + allow_control_characters |= ALLOW_DEFAULT_ANSI_SEQUENCES; + else if (skip_prefix_in_csv(value, "color", &value)) + allow_control_characters |= ALLOW_ANSI_COLOR_SEQUENCES; + else if (skip_prefix_in_csv(value, "cursor", &value)) + allow_control_characters |= ALLOW_ANSI_CURSOR_MOVEMENTS; + else if (skip_prefix_in_csv(value, "erase", &value)) + allow_control_characters |= ALLOW_ANSI_ERASE; + else if (skip_prefix_in_csv(value, "true", &value)) + allow_control_characters = ALLOW_ALL_CONTROL_CHARACTERS; + else if (skip_prefix_in_csv(value, "false", &value)) + allow_control_characters = ALLOW_NO_CONTROL_CHARACTERS; + else + warning(_("unrecognized value for `sideband." + "allowControlCharacters`: '%s'"), value); + } +} /* Returns a color setting (GIT_COLOR_NEVER, etc). */ static int use_sideband_colors(void) @@ -54,13 +88,8 @@ static int use_sideband_colors(void) if (git_config_get_string_tmp("sideband.allowcontrolcharacters", &value)) ; /* huh? `get_maybe_bool()` returned -1 */ - else if (!strcmp(value, "default")) - allow_control_characters = ALLOW_DEFAULT_ANSI_SEQUENCES; - else if (!strcmp(value, "color")) - allow_control_characters = ALLOW_ANSI_COLOR_SEQUENCES; else - warning(_("unrecognized value for `sideband." - "allowControlCharacters`: '%s'"), value); + parse_allow_control_characters(value); break; default: break; /* not configured */ @@ -93,7 +122,7 @@ void list_config_color_sideband_slots(struct string_list *list, const char *pref list_config_item(list, prefix, keywords[i].keyword); } -static int handle_ansi_color_sequence(struct strbuf *dest, const char *src, int n) +static int handle_ansi_sequence(struct strbuf *dest, const char *src, int n) { int i; @@ -105,14 +134,47 @@ static int handle_ansi_color_sequence(struct strbuf *dest, const char *src, int * These are part of the Select Graphic Rendition sequences which * contain more than just color sequences, for more details see * https://en.wikipedia.org/wiki/ANSI_escape_code#SGR. + * + * The cursor movement sequences are: + * + * ESC [ n A - Cursor up n lines (CUU) + * ESC [ n B - Cursor down n lines (CUD) + * ESC [ n C - Cursor forward n columns (CUF) + * ESC [ n D - Cursor back n columns (CUB) + * ESC [ n E - Cursor next line, beginning (CNL) + * ESC [ n F - Cursor previous line, beginning (CPL) + * ESC [ n G - Cursor to column n (CHA) + * ESC [ n ; m H - Cursor position (row n, col m) (CUP) + * ESC [ n ; m f - Same as H (HVP) + * + * The sequences to erase characters are: + * + * + * ESC [ 0 J - Clear from cursor to end of screen (ED) + * ESC [ 1 J - Clear from cursor to beginning of screen (ED) + * ESC [ 2 J - Clear entire screen (ED) + * ESC [ 3 J - Clear entire screen + scrollback (ED) - xterm extension + * ESC [ 0 K - Clear from cursor to end of line (EL) + * ESC [ 1 K - Clear from cursor to beginning of line (EL) + * ESC [ 2 K - Clear entire line (EL) + * ESC [ n M - Delete n lines (DL) + * ESC [ n P - Delete n characters (DCH) + * ESC [ n X - Erase n characters (ECH) + * + * For a comprehensive list of common ANSI Escape sequences, see + * https://www.xfree86.org/current/ctlseqs.html */ - if (allow_control_characters != ALLOW_ANSI_COLOR_SEQUENCES || - n < 3 || src[0] != '\x1b' || src[1] != '[') + if (n < 3 || src[0] != '\x1b' || src[1] != '[') return 0; for (i = 2; i < n; i++) { - if (src[i] == 'm') { + if (((allow_control_characters & ALLOW_ANSI_COLOR_SEQUENCES) && + src[i] == 'm') || + ((allow_control_characters & ALLOW_ANSI_CURSOR_MOVEMENTS) && + strchr("ABCDEFGHf", src[i])) || + ((allow_control_characters & ALLOW_ANSI_ERASE) && + strchr("JKMPX", src[i]))) { strbuf_add(dest, src, i + 1); return i; } @@ -127,7 +189,7 @@ static void strbuf_add_sanitized(struct strbuf *dest, const char *src, int n) { int i; - if (allow_control_characters == ALLOW_ALL_CONTROL_CHARACTERS) { + if ((allow_control_characters & ALLOW_ALL_CONTROL_CHARACTERS)) { strbuf_add(dest, src, n); return; } @@ -136,7 +198,8 @@ static void strbuf_add_sanitized(struct strbuf *dest, const char *src, int n) for (; n && *src; src++, n--) { if (!iscntrl(*src) || *src == '\t' || *src == '\n') { strbuf_addch(dest, *src); - } else if ((i = handle_ansi_color_sequence(dest, src, n))) { + } else if (allow_control_characters != ALLOW_NO_CONTROL_CHARACTERS && + (i = handle_ansi_sequence(dest, src, n))) { src += i; n -= i; } else { diff --git a/t/t5409-colorize-remote-messages.sh b/t/t5409-colorize-remote-messages.sh index f34977b332..c3e4e14362 100755 --- a/t/t5409-colorize-remote-messages.sh +++ b/t/t5409-colorize-remote-messages.sh @@ -129,4 +129,42 @@ test_expect_success 'disallow (color) control sequences in sideband' ' test_file_not_empty actual ' +test_decode_csi() { + awk '{ + while (match($0, /\033/) != 0) { + printf "%sCSI ", substr($0, 1, RSTART-1); + $0 = substr($0, RSTART + RLENGTH, length($0) - RSTART - RLENGTH + 1); + } + print + }' +} + +test_expect_success 'control sequences in sideband allowed by default' ' + write_script .git/color-me-surprised <<-\EOF && + printf "error: \\033[31mcolor\\033[m\\033[Goverwrite\\033[Gerase\\033[K\\033?25l\\n" >&2 + exec "$@" + EOF + test_config_global uploadPack.packObjectsHook ./color-me-surprised && + test_commit need-at-least-one-commit-at-least && + + rm -rf throw-away && + git clone --no-local . throw-away 2>stderr && + test_decode_color color-decoded && + test_decode_csi decoded && + test_grep ! "CSI \\[K" decoded && + test_grep ! "CSI \\[G" decoded && + test_grep "\\^\\[?25l" decoded && + + rm -rf throw-away && + git -c sideband.allowControlCharacters=erase,cursor,color \ + clone --no-local . throw-away 2>stderr && + test_decode_color color-decoded && + test_decode_csi decoded && + test_grep "RED" decoded && + test_grep "CSI \\[K" decoded && + test_grep "CSI \\[G" decoded && + test_grep ! "\\^\\[\\[K" decoded && + test_grep ! "\\^\\[\\[G" decoded +' + test_done -- gitgitgadget