util: split out escaping code into escape.[ch]

This really deserves its own file, given how much code this is now.

1 files changed, 480 insertions, 0 deletions

diff --git a/src/basic/escape.c b/src/basic/escape.c
new file mode 100644
index 0000000000..cf05ce10ef
--- /dev/null
+++ b/src/basic/escape.c
@@ -0,0 +1,480 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright 2010 Lennart Poettering
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include "utf8.h"
+#include "util.h"
+
+#include "escape.h"
+
+size_t cescape_char(char c, char *buf) {
+        char * buf_old = buf;
+
+        switch (c) {
+
+                case '\a':
+                        *(buf++) = '\\';
+                        *(buf++) = 'a';
+                        break;
+                case '\b':
+                        *(buf++) = '\\';
+                        *(buf++) = 'b';
+                        break;
+                case '\f':
+                        *(buf++) = '\\';
+                        *(buf++) = 'f';
+                        break;
+                case '\n':
+                        *(buf++) = '\\';
+                        *(buf++) = 'n';
+                        break;
+                case '\r':
+                        *(buf++) = '\\';
+                        *(buf++) = 'r';
+                        break;
+                case '\t':
+                        *(buf++) = '\\';
+                        *(buf++) = 't';
+                        break;
+                case '\v':
+                        *(buf++) = '\\';
+                        *(buf++) = 'v';
+                        break;
+                case '\\':
+                        *(buf++) = '\\';
+                        *(buf++) = '\\';
+                        break;
+                case '"':
+                        *(buf++) = '\\';
+                        *(buf++) = '"';
+                        break;
+                case '\'':
+                        *(buf++) = '\\';
+                        *(buf++) = '\'';
+                        break;
+
+                default:
+                        /* For special chars we prefer octal over
+                         * hexadecimal encoding, simply because glib's
+                         * g_strescape() does the same */
+                        if ((c < ' ') || (c >= 127)) {
+                                *(buf++) = '\\';
+                                *(buf++) = octchar((unsigned char) c >> 6);
+                                *(buf++) = octchar((unsigned char) c >> 3);
+                                *(buf++) = octchar((unsigned char) c);
+                        } else
+                                *(buf++) = c;
+                        break;
+        }
+
+        return buf - buf_old;
+}
+
+char *cescape(const char *s) {
+        char *r, *t;
+        const char *f;
+
+        assert(s);
+
+        /* Does C style string escaping. May be reversed with
+         * cunescape(). */
+
+        r = new(char, strlen(s)*4 + 1);
+        if (!r)
+                return NULL;
+
+        for (f = s, t = r; *f; f++)
+                t += cescape_char(*f, t);
+
+        *t = 0;
+
+        return r;
+}
+
+int cunescape_one(const char *p, size_t length, char *ret, uint32_t *ret_unicode) {
+        int r = 1;
+
+        assert(p);
+        assert(*p);
+        assert(ret);
+
+        /* Unescapes C style. Returns the unescaped character in ret,
+         * unless we encountered a \u sequence in which case the full
+         * unicode character is returned in ret_unicode, instead. */
+
+        if (length != (size_t) -1 && length < 1)
+                return -EINVAL;
+
+        switch (p[0]) {
+
+        case 'a':
+                *ret = '\a';
+                break;
+        case 'b':
+                *ret = '\b';
+                break;
+        case 'f':
+                *ret = '\f';
+                break;
+        case 'n':
+                *ret = '\n';
+                break;
+        case 'r':
+                *ret = '\r';
+                break;
+        case 't':
+                *ret = '\t';
+                break;
+        case 'v':
+                *ret = '\v';
+                break;
+        case '\\':
+                *ret = '\\';
+                break;
+        case '"':
+                *ret = '"';
+                break;
+        case '\'':
+                *ret = '\'';
+                break;
+
+        case 's':
+                /* This is an extension of the XDG syntax files */
+                *ret = ' ';
+                break;
+
+        case 'x': {
+                /* hexadecimal encoding */
+                int a, b;
+
+                if (length != (size_t) -1 && length < 3)
+                        return -EINVAL;
+
+                a = unhexchar(p[1]);
+                if (a < 0)
+                        return -EINVAL;
+
+                b = unhexchar(p[2]);
+                if (b < 0)
+                        return -EINVAL;
+
+                /* Don't allow NUL bytes */
+                if (a == 0 && b == 0)
+                        return -EINVAL;
+
+                *ret = (char) ((a << 4U) | b);
+                r = 3;
+                break;
+        }
+
+        case 'u': {
+                /* C++11 style 16bit unicode */
+
+                int a[4];
+                unsigned i;
+                uint32_t c;
+
+                if (length != (size_t) -1 && length < 5)
+                        return -EINVAL;
+
+                for (i = 0; i < 4; i++) {
+                        a[i] = unhexchar(p[1 + i]);
+                        if (a[i] < 0)
+                                return a[i];
+                }
+
+                c = ((uint32_t) a[0] << 12U) | ((uint32_t) a[1] << 8U) | ((uint32_t) a[2] << 4U) | (uint32_t) a[3];
+
+                /* Don't allow 0 chars */
+                if (c == 0)
+                        return -EINVAL;
+
+                if (c < 128)
+                        *ret = c;
+                else {
+                        if (!ret_unicode)
+                                return -EINVAL;
+
+                        *ret = 0;
+                        *ret_unicode = c;
+                }
+
+                r = 5;
+                break;
+        }
+
+        case 'U': {
+                /* C++11 style 32bit unicode */
+
+                int a[8];
+                unsigned i;
+                uint32_t c;
+
+                if (length != (size_t) -1 && length < 9)
+                        return -EINVAL;
+
+                for (i = 0; i < 8; i++) {
+                        a[i] = unhexchar(p[1 + i]);
+                        if (a[i] < 0)
+                                return a[i];
+                }
+
+                c = ((uint32_t) a[0] << 28U) | ((uint32_t) a[1] << 24U) | ((uint32_t) a[2] << 20U) | ((uint32_t) a[3] << 16U) |
+                    ((uint32_t) a[4] << 12U) | ((uint32_t) a[5] <<  8U) | ((uint32_t) a[6] <<  4U) |  (uint32_t) a[7];
+
+                /* Don't allow 0 chars */
+                if (c == 0)
+                        return -EINVAL;
+
+                /* Don't allow invalid code points */
+                if (!unichar_is_valid(c))
+                        return -EINVAL;
+
+                if (c < 128)
+                        *ret = c;
+                else {
+                        if (!ret_unicode)
+                                return -EINVAL;
+
+                        *ret = 0;
+                        *ret_unicode = c;
+                }
+
+                r = 9;
+                break;
+        }
+
+        case '0':
+        case '1':
+        case '2':
+        case '3':
+        case '4':
+        case '5':
+        case '6':
+        case '7': {
+                /* octal encoding */
+                int a, b, c;
+                uint32_t m;
+
+                if (length != (size_t) -1 && length < 3)
+                        return -EINVAL;
+
+                a = unoctchar(p[0]);
+                if (a < 0)
+                        return -EINVAL;
+
+                b = unoctchar(p[1]);
+                if (b < 0)
+                        return -EINVAL;
+
+                c = unoctchar(p[2]);
+                if (c < 0)
+                        return -EINVAL;
+
+                /* don't allow NUL bytes */
+                if (a == 0 && b == 0 && c == 0)
+                        return -EINVAL;
+
+                /* Don't allow bytes above 255 */
+                m = ((uint32_t) a << 6U) | ((uint32_t) b << 3U) | (uint32_t) c;
+                if (m > 255)
+                        return -EINVAL;
+
+                *ret = m;
+                r = 3;
+                break;
+        }
+
+        default:
+                return -EINVAL;
+        }
+
+        return r;
+}
+
+int cunescape_length_with_prefix(const char *s, size_t length, const char *prefix, UnescapeFlags flags, char **ret) {
+        char *r, *t;
+        const char *f;
+        size_t pl;
+
+        assert(s);
+        assert(ret);
+
+        /* Undoes C style string escaping, and optionally prefixes it. */
+
+        pl = prefix ? strlen(prefix) : 0;
+
+        r = new(char, pl+length+1);
+        if (!r)
+                return -ENOMEM;
+
+        if (prefix)
+                memcpy(r, prefix, pl);
+
+        for (f = s, t = r + pl; f < s + length; f++) {
+                size_t remaining;
+                uint32_t u;
+                char c;
+                int k;
+
+                remaining = s + length - f;
+                assert(remaining > 0);
+
+                if (*f != '\\') {
+                        /* A literal literal, copy verbatim */
+                        *(t++) = *f;
+                        continue;
+                }
+
+                if (remaining == 1) {
+                        if (flags & UNESCAPE_RELAX) {
+                                /* A trailing backslash, copy verbatim */
+                                *(t++) = *f;
+                                continue;
+                        }
+
+                        free(r);
+                        return -EINVAL;
+                }
+
+                k = cunescape_one(f + 1, remaining - 1, &c, &u);
+                if (k < 0) {
+                        if (flags & UNESCAPE_RELAX) {
+                                /* Invalid escape code, let's take it literal then */
+                                *(t++) = '\\';
+                                continue;
+                        }
+
+                        free(r);
+                        return k;
+                }
+
+                if (c != 0)
+                        /* Non-Unicode? Let's encode this directly */
+                        *(t++) = c;
+                else
+                        /* Unicode? Then let's encode this in UTF-8 */
+                        t += utf8_encode_unichar(t, u);
+
+                f += k;
+        }
+
+        *t = 0;
+
+        *ret = r;
+        return t - r;
+}
+
+int cunescape_length(const char *s, size_t length, UnescapeFlags flags, char **ret) {
+        return cunescape_length_with_prefix(s, length, NULL, flags, ret);
+}
+
+int cunescape(const char *s, UnescapeFlags flags, char **ret) {
+        return cunescape_length(s, strlen(s), flags, ret);
+}
+
+char *xescape(const char *s, const char *bad) {
+        char *r, *t;
+        const char *f;
+
+        /* Escapes all chars in bad, in addition to \ and all special
+         * chars, in \xFF style escaping. May be reversed with
+         * cunescape(). */
+
+        r = new(char, strlen(s) * 4 + 1);
+        if (!r)
+                return NULL;
+
+        for (f = s, t = r; *f; f++) {
+
+                if ((*f < ' ') || (*f >= 127) ||
+                    (*f == '\\') || strchr(bad, *f)) {
+                        *(t++) = '\\';
+                        *(t++) = 'x';
+                        *(t++) = hexchar(*f >> 4);
+                        *(t++) = hexchar(*f);
+                } else
+                        *(t++) = *f;
+        }
+
+        *t = 0;
+
+        return r;
+}
+
+static char *strcpy_backslash_escaped(char *t, const char *s, const char *bad) {
+        assert(bad);
+
+        for (; *s; s++) {
+                if (*s == '\\' || strchr(bad, *s))
+                        *(t++) = '\\';
+
+                *(t++) = *s;
+        }
+
+        return t;
+}
+
+char *shell_escape(const char *s, const char *bad) {
+        char *r, *t;
+
+        r = new(char, strlen(s)*2+1);
+        if (!r)
+                return NULL;
+
+        t = strcpy_backslash_escaped(r, s, bad);
+        *t = 0;
+
+        return r;
+}
+
+char *shell_maybe_quote(const char *s) {
+        const char *p;
+        char *r, *t;
+
+        assert(s);
+
+        /* Encloses a string in double quotes if necessary to make it
+         * OK as shell string. */
+
+        for (p = s; *p; p++)
+                if (*p <= ' ' ||
+                    *p >= 127 ||
+                    strchr(SHELL_NEED_QUOTES, *p))
+                        break;
+
+        if (!*p)
+                return strdup(s);
+
+        r = new(char, 1+strlen(s)*2+1+1);
+        if (!r)
+                return NULL;
+
+        t = r;
+        *(t++) = '"';
+        t = mempcpy(t, s, p - s);
+
+        t = strcpy_backslash_escaped(t, p, SHELL_NEED_ESCAPE);
+
+        *(t++)= '"';
+        *t = 0;
+
+        return r;
+}