ptyfwd: optionally, change ANSI background color of forwarded terminals
As the bytes flow through our terminal forwarder we can color the background of the terminal with a color of our choices, if that's desired. This will later allow us to color the background of the uid0 tool when running as root with a slightly alarming red color. This does two things: 1. When an ANSI sequence is seen that resets the background color, it is extended to immediately set the color to our choice. 2. When a newline is seen it is immeidately extended to set the background color again and clear the current line till the end. Net effect: all lines written while we forward the ttys will be shown with the background color of choice.
This commit is contained in:
Lennart Poettering
+274
-5
@@ -18,15 +18,26 @@
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#include "alloc-util.h"
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#include "errno-util.h"
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#include "extract-word.h"
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#include "fd-util.h"
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#include "io-util.h"
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#include "log.h"
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#include "macro.h"
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#include "ptyfwd.h"
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#include "stat-util.h"
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#include "strv.h"
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#include "terminal-util.h"
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#include "time-util.h"
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typedef enum AnsiColorState {
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ANSI_COLOR_STATE_TEXT,
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ANSI_COLOR_STATE_ESC,
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ANSI_COLOR_STATE_CSI_SEQUENCE,
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ANSI_COLOR_STATE_NEWLINE,
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_ANSI_COLOR_STATE_MAX,
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_ANSI_COLOR_STATE_INVALID = -EINVAL,
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} AnsiColorState;
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struct PTYForward {
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sd_event *event;
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@@ -67,7 +78,8 @@ struct PTYForward {
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bool last_char_set:1;
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char last_char;
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char in_buffer[LINE_MAX], out_buffer[LINE_MAX];
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char in_buffer[LINE_MAX], *out_buffer;
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size_t out_buffer_size;
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size_t in_buffer_full, out_buffer_full;
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usec_t escape_timestamp;
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@@ -75,6 +87,10 @@ struct PTYForward {
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PTYForwardHandler handler;
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void *userdata;
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char *background_color;
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AnsiColorState ansi_color_state;
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char *csi_sequence;
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};
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#define ESCAPE_USEC (1*USEC_PER_SEC)
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@@ -115,6 +131,14 @@ static void pty_forward_disconnect(PTYForward *f) {
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}
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f->saved_stdout = f->saved_stdin = false;
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f->out_buffer = mfree(f->out_buffer);
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f->out_buffer_size = 0;
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f->out_buffer_full = 0;
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f->in_buffer_full = 0;
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f->csi_sequence = mfree(f->csi_sequence);
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f->ansi_color_state = _ANSI_COLOR_STATE_INVALID;
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}
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static int pty_forward_done(PTYForward *f, int rcode) {
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@@ -202,10 +226,243 @@ static bool drained(PTYForward *f) {
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return true;
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}
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static int shovel(PTYForward *f) {
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ssize_t k;
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static char *background_color_sequence(PTYForward *f) {
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assert(f);
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assert(f->background_color);
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/* This sets the background color to the desired one, and erase the rest of the line with it */
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return strjoin("\x1B[", f->background_color, "m", ANSI_ERASE_TO_END_OF_LINE);
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}
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static int insert_string(PTYForward *f, size_t offset, const char *s) {
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assert(f);
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assert(offset <= f->out_buffer_full);
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assert(s);
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size_t l = strlen(s);
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assert(l <= INT_MAX); /* Make sure we can still return this */
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void *p = realloc(f->out_buffer, MAX(f->out_buffer_full + l, (size_t) LINE_MAX));
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if (!p)
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return -ENOMEM;
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f->out_buffer = p;
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f->out_buffer_size = MALLOC_SIZEOF_SAFE(f->out_buffer);
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memmove(f->out_buffer + offset + l, f->out_buffer + offset, f->out_buffer_full - offset);
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memcpy(f->out_buffer + offset, s, l);
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f->out_buffer_full += l;
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return (int) l;
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}
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static int insert_erase_newline(PTYForward *f, size_t offset) {
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_cleanup_free_ char *s = NULL;
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assert(f);
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assert(f->background_color);
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s = background_color_sequence(f);
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if (!s)
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return -ENOMEM;
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return insert_string(f, offset, s);
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}
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static int is_csi_background_reset_sequence(const char *seq) {
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enum {
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COLOR_TOKEN_NO,
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COLOR_TOKEN_START,
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COLOR_TOKEN_8BIT,
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COLOR_TOKEN_24BIT_R,
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COLOR_TOKEN_24BIT_G,
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COLOR_TOKEN_24BIT_B,
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} token_state = COLOR_TOKEN_NO;
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bool b = false;
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int r;
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assert(seq);
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/* This parses CSI "m" sequences, and determines if they reset the background color. If so returns
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* 1. This can then be used to insert another sequence that sets the color to the desired
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* replacement. */
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for (;;) {
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_cleanup_free_ char *token = NULL;
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r = extract_first_word(&seq, &token, ";", EXTRACT_RELAX|EXTRACT_DONT_COALESCE_SEPARATORS|EXTRACT_RETAIN_ESCAPE);
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if (r < 0)
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return r;
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if (r == 0)
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break;
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switch (token_state) {
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case COLOR_TOKEN_NO:
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if (STR_IN_SET(token, "", "0", "00", "49"))
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b = true; /* These tokens set the background back to normal */
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else if (STR_IN_SET(token, "40", "41", "42", "43", "44", "45", "46", "47", "48"))
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b = false; /* And these tokens set them to something other than normal */
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if (STR_IN_SET(token, "38", "48", "58"))
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token_state = COLOR_TOKEN_START; /* These tokens mean an 8bit or 24bit color will follow */
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break;
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case COLOR_TOKEN_START:
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if (STR_IN_SET(token, "5", "05"))
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token_state = COLOR_TOKEN_8BIT; /* 8bit color */
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else if (STR_IN_SET(token, "2", "02"))
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token_state = COLOR_TOKEN_24BIT_R; /* 24bit color */
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else
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token_state = COLOR_TOKEN_NO; /* something weird? */
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break;
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case COLOR_TOKEN_24BIT_R:
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token_state = COLOR_TOKEN_24BIT_G;
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break;
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case COLOR_TOKEN_24BIT_G:
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token_state = COLOR_TOKEN_24BIT_B;
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break;
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case COLOR_TOKEN_8BIT:
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case COLOR_TOKEN_24BIT_B:
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token_state = COLOR_TOKEN_NO;
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break;
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}
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}
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return b;
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}
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static int insert_background_fix(PTYForward *f, size_t offset) {
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assert(f);
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assert(f->background_color);
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if (!is_csi_background_reset_sequence(strempty(f->csi_sequence)))
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return 0;
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_cleanup_free_ char *s = NULL;
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s = strjoin(";", f->background_color);
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if (!s)
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return -ENOMEM;
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return insert_string(f, offset, s);
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}
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static int pty_forward_ansi_process(PTYForward *f, size_t offset) {
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int r;
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assert(f);
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assert(offset <= f->out_buffer_full);
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if (!f->background_color)
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return 0;
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for (size_t i = offset; i < f->out_buffer_full; i++) {
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char c = f->out_buffer[i];
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switch (f->ansi_color_state) {
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case ANSI_COLOR_STATE_TEXT:
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if (c == '\n')
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f->ansi_color_state = ANSI_COLOR_STATE_NEWLINE;
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if (c == 0x1B) /* ESC */
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f->ansi_color_state = ANSI_COLOR_STATE_ESC;
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break;
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case ANSI_COLOR_STATE_NEWLINE: {
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/* Immediately after a newline insert an ANSI sequence to erase the line with a background color */
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r = insert_erase_newline(f, i);
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if (r < 0)
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return r;
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i += r;
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f->ansi_color_state = ANSI_COLOR_STATE_TEXT;
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break;
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}
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case ANSI_COLOR_STATE_ESC: {
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if (c == '[')
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f->ansi_color_state = ANSI_COLOR_STATE_CSI_SEQUENCE;
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else
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f->ansi_color_state = ANSI_COLOR_STATE_TEXT;
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break;
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}
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case ANSI_COLOR_STATE_CSI_SEQUENCE: {
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if (c >= 0x20 && c <= 0x3F) {
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/* If this is a "parameter" or "intermediary" byte (i.e. ranges 0x20…0x2F and
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* 0x30…0x3F) then we are still in the CSI sequence */
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if (strlen_ptr(f->csi_sequence) >= 64) {
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/* Safety check: lets not accept unbounded CSI sequences */
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f->csi_sequence = mfree(f->csi_sequence);
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f->ansi_color_state = ANSI_COLOR_STATE_TEXT;
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} else if (!strextend(&f->csi_sequence, CHAR_TO_STR(c)))
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return -ENOMEM;
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} else {
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/* Otherwise, the CSI sequence is over */
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if (c == 'm') {
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/* This is an "SGR" (Select Graphic Rendition) sequence. Patch in our background color. */
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r = insert_background_fix(f, i);
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if (r < 0)
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return r;
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i += r;
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}
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f->csi_sequence = mfree(f->csi_sequence);
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f->ansi_color_state = ANSI_COLOR_STATE_TEXT;
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}
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break;
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}
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default:
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assert_not_reached();
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}
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}
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return 0;
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}
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static int shovel(PTYForward *f) {
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ssize_t k;
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int r;
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assert(f);
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if (f->out_buffer_size == 0 && f->background_color) {
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/* Erase the first line when we start */
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f->out_buffer = background_color_sequence(f);
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if (!f->out_buffer)
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return pty_forward_done(f, log_oom());
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f->out_buffer_full = strlen(f->out_buffer);
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f->out_buffer_size = MALLOC_SIZEOF_SAFE(f->out_buffer);
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}
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if (f->out_buffer_size < LINE_MAX) {
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/* Make sure we always have room for at least one "line" */
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void *p = realloc(f->out_buffer, LINE_MAX);
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if (!p)
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return pty_forward_done(f, log_oom());
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f->out_buffer = p;
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f->out_buffer_size = MALLOC_SIZEOF_SAFE(p);
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}
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while ((f->stdin_readable && f->in_buffer_full <= 0) ||
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(f->master_writable && f->in_buffer_full > 0) ||
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@@ -267,9 +524,9 @@ static int shovel(PTYForward *f) {
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}
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}
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if (f->master_readable && f->out_buffer_full < LINE_MAX) {
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if (f->master_readable && f->out_buffer_full < MIN(f->out_buffer_size, (size_t) LINE_MAX)) {
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k = read(f->master, f->out_buffer + f->out_buffer_full, LINE_MAX - f->out_buffer_full);
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k = read(f->master, f->out_buffer + f->out_buffer_full, f->out_buffer_size - f->out_buffer_full);
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if (k < 0) {
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/* Note that EIO on the master device might be caused by vhangup() or
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@@ -289,7 +546,12 @@ static int shovel(PTYForward *f) {
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}
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} else {
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f->read_from_master = true;
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size_t scan_index = f->out_buffer_full;
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f->out_buffer_full += (size_t) k;
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r = pty_forward_ansi_process(f, scan_index);
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if (r < 0)
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return pty_forward_done(f, log_error_errno(r, "Failed to scan for ANSI sequences: %m"));
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}
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}
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@@ -555,6 +817,7 @@ PTYForward *pty_forward_free(PTYForward *f) {
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if (!f)
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return NULL;
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pty_forward_disconnect(f);
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free(f->background_color);
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return mfree(f);
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}
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@@ -689,3 +952,9 @@ int pty_forward_set_width_height(PTYForward *f, unsigned width, unsigned height)
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return 0;
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}
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int pty_forward_set_background_color(PTYForward *f, const char *color) {
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assert(f);
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return free_and_strdup(&f->background_color, color);
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}
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@@ -39,4 +39,6 @@ int pty_forward_set_priority(PTYForward *f, int64_t priority);
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int pty_forward_set_width_height(PTYForward *f, unsigned width, unsigned height);
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int pty_forward_set_background_color(PTYForward *f, const char *color);
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DEFINE_TRIVIAL_CLEANUP_FUNC(PTYForward*, pty_forward_free);
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