regex.c

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/*
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation; either version 2 of the License, or
 *   (at your option) any later version.
 *
 *   This program 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 General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program; if not, write to the Free Software
 *   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
 */
 
/** Wrappers around various regular expression libraries
 *
 * @file src/lib/util/regex.c
 *
 * @copyright 2014 The FreeRADIUS server project
 * @copyright 2014 Arran Cudbard-Bell (a.cudbardb@freeradius.org)
 */
RCSID("$Id: a35167f856c5ceb8744a2cd3cdbf7a523950a57a $")
 
#ifdef HAVE_REGEX
 
#include <freeradius-devel/util/regex.h>
 
#if defined(HAVE_REGEX_PCRE2) && defined(PCRE2_CONFIG_JIT)
#ifndef FR_PCRE_JIT_STACK_MIN
#  define FR_PCRE_JIT_STACK_MIN (128 * 1024)
#endif
#ifndef FR_PCRE_JIT_STACK_MAX
#  define FR_PCRE_JIT_STACK_MAX (512 * 1024)
#endif
#endif
 
/*
 *      pcre2_set_max_pattern_compiled_length() arrived in PCRE2 10.41.
 */
#if defined(HAVE_REGEX_PCRE2) && defined(PCRE2_MAJOR) && \
        ((PCRE2_MAJOR > 10) || ((PCRE2_MAJOR == 10) && (PCRE2_MINOR >= 41)))
#  define FR_PCRE2_HAVE_MAX_PATTERN_LENGTH 1
 
/*
 *      The largest a single pattern may compile to.
 *
 *      A bounded repeat is expanded by the engine, and nesting them
 *      multiplies: "((((a){40}){40}){40}){40}" is 25 characters, and expands
 *      to around 40^4 nodes.  With no limit, a pattern of a few dozen bytes
 *      compiles to gigabytes.  That matters because regex_compile() runs at
 *      runtime as well as at config time, see xlat_func_regex_search().
 *
 *      Hand-written patterns compile to a few KB at most, so this bound is
 *      orders of magnitude above anything legitimate, and only fires on
 *      patterns built to exhaust memory.
 */
#  ifndef FR_PCRE2_MAX_PATTERN_LENGTH
#    define FR_PCRE2_MAX_PATTERN_LENGTH (1024 * 1024)
#  endif
#endif
 
const fr_sbuff_escape_rules_t regex_escape_rules = {
        .name = "regex",
        .chr = '\\',
        .subs = {
                ['$'] = '$',
                ['*'] = '*',
                ['+'] = '+',
                ['.'] = '.',
                ['/'] = '/',
                ['?'] = '?',
                ['('] = '(',
                [')'] = ')',
                ['['] = '[',
                [']'] = ']',
                ['{'] = '{',
                ['}'] = '}',
                ['\\'] = '\\',
                ['^'] = '^',
                ['`'] = '`',
                ['|'] = '|',
                ['\a'] = 'a',
                ['\b'] = 'b',
                ['\n'] = 'n',
                ['\r'] = 'r',
                ['\t'] = 't',
                ['\v'] = 'v'
        },
        .esc = {
                SBUFF_CHAR_UNPRINTABLES_LOW,
                SBUFF_CHAR_UNPRINTABLES_EXTENDED
        },
        .do_utf8 = true,
        .do_oct = true
};
 
 
/*
 *######################################
 *#      FUNCTIONS FOR LIBPCRE2        #
 *######################################
 */
#ifdef HAVE_REGEX_PCRE2
/*
 *      Wrapper functions for libpcre2. Much more powerful, and guaranteed
 *      to be binary safe for both patterns and subjects but require
 *      libpcre2.
 */
 
/** Thread local storage for PCRE2
 *
 * Not all this storage is thread local, but it simplifies cleanup if
 * we bind its lifetime to the thread, and lets us get away with not
 * having specific init/free functions.
 */
typedef struct {
        TALLOC_CTX              *alloc_ctx;     //!< Context used for any allocations.
        pcre2_general_context   *gcontext;      //!< General context.
        pcre2_compile_context   *ccontext;      //!< Compile context.
        pcre2_match_context     *mcontext;      //!< Match context.
#ifdef PCRE2_CONFIG_JIT
        pcre2_jit_stack         *jit_stack;     //!< Jit stack for executing jit'd patterns.
        bool                    do_jit;         //!< Whether we have runtime JIT support.
#endif
} fr_pcre2_tls_t;
 
/** Thread local storage for pcre2
 *
 */
static _Thread_local fr_pcre2_tls_t *fr_pcre2_tls;
 
/** Talloc wrapper for pcre2 memory allocation
 *
 * @param[in] to_alloc          How many bytes to alloc.
 * @param[in] uctx              UNUSED.
 */
static void *_pcre2_talloc(PCRE2_SIZE to_alloc, UNUSED void *uctx)
{
        return talloc_array(fr_pcre2_tls->alloc_ctx, uint8_t, to_alloc);
}
 
/** Talloc wrapper for pcre2 memory freeing
 *
 * @param[in] to_free           Memory to free.
 * @param[in] uctx              UNUSED.
 */
static void _pcre2_talloc_free(void *to_free, UNUSED void *uctx)
{
        talloc_free(to_free);
}
 
/** Free thread local data
 *
 * @param[in] tls       Thread local data to free.
 */
static int _pcre2_tls_free(fr_pcre2_tls_t *tls)
{
        if (tls->gcontext) pcre2_general_context_free(tls->gcontext);
        if (tls->ccontext) pcre2_compile_context_free(tls->ccontext);
        if (tls->mcontext) pcre2_match_context_free(tls->mcontext);
#ifdef PCRE2_CONFIG_JIT
        if (tls->jit_stack) pcre2_jit_stack_free(tls->jit_stack);
#endif
 
        return 0;
}
 
static int _pcre2_tls_free_on_exit(void *arg)
{
        return talloc_free(arg);
}
 
/** Thread local init for pcre2
 *
 */
static int fr_pcre2_tls_init(void)
{
        fr_pcre2_tls_t *tls;
 
        if (unlikely(fr_pcre2_tls != NULL)) return 0;
 
        fr_pcre2_tls = tls = talloc_zero(NULL, fr_pcre2_tls_t);
        if (!tls) return -1;
        talloc_set_destructor(tls, _pcre2_tls_free);
 
        tls->gcontext = pcre2_general_context_create(_pcre2_talloc, _pcre2_talloc_free, NULL);
        if (!tls->gcontext) {
                fr_strerror_const("Failed allocating general context");
                return -1;
        }
 
        tls->ccontext = pcre2_compile_context_create(tls->gcontext);
        if (!tls->ccontext) {
                fr_strerror_const("Failed allocating compile context");
        error:
                fr_pcre2_tls = NULL;
                _pcre2_tls_free(tls);
                return -1;
        }
 
#ifdef FR_PCRE2_HAVE_MAX_PATTERN_LENGTH
        /*
         *      Cap memory usage.  Patterns over this limit will fail
         *      with an error in pcre2_compile() or regex_compile().
         */
        pcre2_set_max_pattern_length(tls->ccontext, FR_PCRE2_MAX_PATTERN_LENGTH);
#endif
 
        tls->mcontext = pcre2_match_context_create(tls->gcontext);
        if (!tls->mcontext) {
                fr_strerror_const("Failed allocating match context");
                goto error;
        }
 
#ifdef PCRE2_CONFIG_JIT
        pcre2_config(PCRE2_CONFIG_JIT, &tls->do_jit);
        if (tls->do_jit) {
                tls->jit_stack = pcre2_jit_stack_create(FR_PCRE_JIT_STACK_MIN, FR_PCRE_JIT_STACK_MAX, tls->gcontext);
                if (!tls->jit_stack) {
                        fr_strerror_const("Failed allocating JIT stack");
                        goto error;
                }
                pcre2_jit_stack_assign(tls->mcontext, NULL, tls->jit_stack);
        }
#endif
 
        /*
         *      Free on thread exit
         */
        fr_atexit_thread_local(fr_pcre2_tls, _pcre2_tls_free_on_exit, tls);
        fr_pcre2_tls = tls;     /* Assign to thread local storage */
 
        return 0;
}
 
/** Free regex_t structure
 *
 * Calls libpcre specific free functions for the expression and study.
 *
 * @param preg to free.
 */
static int _regex_free(regex_t *preg)
{
        if (preg->compiled) pcre2_code_free(preg->compiled);
 
        return 0;
}
 
/** Wrapper around pcre2_compile
 *
 * Allows the rest of the code to do compilations using one function signature.
 *
 * @note Compiled expression must be freed with talloc_free.
 *
 * @param[out] out              Where to write out a pointer to the structure containing
 *                              the compiled expression.
 * @param[in] pattern           to compile.
 * @param[in] len               of pattern.
 * @param[in] flags             controlling matching. May be NULL.
 * @param[in] subcaptures       Whether to compile the regular expression to store subcapture
 *                              data.
 * @param[in] runtime           If false run the pattern through the PCRE JIT (if available)
 *                              to convert it to machine code. This trades startup time (longer)
 *                              for runtime performance (better).
 * @return
 *      - >= 1 on success.
 *      - <= 0 on error. Negative value is offset of parse error.
 */
ssize_t regex_compile(TALLOC_CTX *ctx, regex_t **out, char const *pattern, size_t len,
                      fr_regex_flags_t const *flags, bool subcaptures, bool runtime)
{
        int             ret;
        PCRE2_SIZE      offset;
        uint32_t        cflags = 0;
        regex_t         *preg;
 
        /*
         *      Check inputs
         */
        *out = NULL;
 
        /*
         *      Thread local initialisation
         */
        if (unlikely(!fr_pcre2_tls) && (fr_pcre2_tls_init() < 0)) return -1;
 
        if (len == 0) {
                fr_strerror_const("Empty expression");
                return 0;
        }
 
        /*
         *      Options
         */
        if (flags) {
                 /* flags->global implemented by substitution function */
                if (flags->ignore_case) cflags |= PCRE2_CASELESS;
                if (flags->multiline) cflags |= PCRE2_MULTILINE;
                if (flags->dot_all) cflags |= PCRE2_DOTALL;
                if (flags->unicode) cflags |= PCRE2_UTF;
                if (flags->extended) cflags |= PCRE2_EXTENDED;
        }
 
        if (!subcaptures) cflags |= PCRE2_NO_AUTO_CAPTURE;
 
        preg = talloc_zero(ctx, regex_t);
        talloc_set_destructor(preg, _regex_free);
 
        preg->compiled = pcre2_compile((PCRE2_SPTR8)pattern, len,
                                       cflags, &ret, &offset, fr_pcre2_tls->ccontext);
        if (!preg->compiled) {
                PCRE2_UCHAR errbuff[128];
 
                pcre2_get_error_message(ret, errbuff, sizeof(errbuff));
                fr_strerror_printf("%s", (char *)errbuff);
                talloc_free(preg);
 
                return -(ssize_t)offset;
        }
 
        if (!runtime) {
                preg->precompiled = true;
 
#ifdef PCRE2_CONFIG_JIT
                /*
                 *      This is expensive, so only do it for
                 *      expressions that are going to be
                 *      evaluated repeatedly.
                 */
                if (fr_pcre2_tls->do_jit) {
                        ret = pcre2_jit_compile(preg->compiled, PCRE2_JIT_COMPLETE);
                        if (ret < 0) {
                                PCRE2_UCHAR errbuff[128];
 
                                pcre2_get_error_message(ret, errbuff, sizeof(errbuff));
                                fr_strerror_printf("Pattern JIT failed: %s", (char *)errbuff);
                                talloc_free(preg);
 
                                return 0;
                        }
                        preg->jitd = true;
                }
#endif
        }
 
        *out = preg;
 
        return len;
}
 
/** Wrapper around pcre2_exec
 *
 * @param[in] preg      The compiled expression.
 * @param[in] subject   to match.
 * @param[in] len       Length of subject.
 * @param[in] regmatch  Array of match pointers.
 * @return
 *      - -1 on failure.
 *      - 0 on no match.
 *      - 1 on match.
 */
int regex_exec(regex_t *preg, char const *subject, size_t len, fr_regmatch_t *regmatch)
{
        int                     ret;
        uint32_t                options = 0;
 
        char                    *our_subject = NULL;
        bool                    dup_subject = true;
        pcre2_match_data        *match_data;
 
        /*
         *      Thread local initialisation
         */
        if (unlikely(!fr_pcre2_tls) && (fr_pcre2_tls_init() < 0)) return -1;
 
        if (regmatch) {
#ifdef PCRE2_COPY_MATCHED_SUBJECT
                /*
                 *      This is apparently only supported for pcre2_match
                 *      NOT pcre2_jit_match.
                 */
#  ifdef PCRE2_CONFIG_JIT
                if (!preg->jitd) {
#  endif
                        dup_subject = false;
 
                        /*
                         *      If PCRE2_COPY_MATCHED_SUBJECT is available
                         *      and set as an options flag, pcre2_match will
                         *      strdup the subject string if pcre2_match is
                         *      successful and store a pointer to it in the
                         *      regmatch struct.
                         *
                         *      The lifetime of the string memory will be
                         *      bound to the regmatch struct.  This is more
                         *      efficient that doing it ourselves, as the
                         *      strdup only occurs if the subject matches.
                         */
                        options |= PCRE2_COPY_MATCHED_SUBJECT;
#  ifdef PCRE2_CONFIG_JIT
                }
#  endif
#endif
                if (dup_subject) {
                        /*
                         *      We have to dup and operate on the duplicate
                         *      of the subject, because pcre2_jit_match and
                         *      pcre2_match store a pointer to the subject
                         *      in the regmatch structure.
                         */
                        subject = our_subject = talloc_bstrndup(regmatch, subject, len);
                        if (!subject) {
                                fr_strerror_const("Out of memory");
                                return -1;
                        }
#ifndef NDEBUG
                        regmatch->subject = subject; /* Stored only for tracking memory issues */
#endif
                }
        }
 
        /*
         *      If we weren't given match data we
         *      need to alloc it else pcre2_match
         *      fails when passed NULL match data.
         */
        if (!regmatch) {
                match_data = pcre2_match_data_create_from_pattern(preg->compiled, fr_pcre2_tls->gcontext);
                if (!match_data) {
                        fr_strerror_const("Failed allocating temporary match data");
                        return -1;
                }
        } else {
                match_data = regmatch->match_data;
        }
 
#ifdef PCRE2_CONFIG_JIT
        if (preg->jitd) {
                ret = pcre2_jit_match(preg->compiled, (PCRE2_SPTR8)subject, len, 0, options,
                                      match_data, fr_pcre2_tls->mcontext);
        } else
#endif
        {
                ret = pcre2_match(preg->compiled, (PCRE2_SPTR8)subject, len, 0, options,
                                  match_data, fr_pcre2_tls->mcontext);
        }
        if (!regmatch) pcre2_match_data_free(match_data);
        if (ret < 0) {
                PCRE2_UCHAR     errbuff[128];
 
                if (dup_subject) talloc_free(our_subject);
 
                if (ret == PCRE2_ERROR_NOMATCH) {
                        if (regmatch) regmatch->used = 0;
                        return 0;
                }
 
                pcre2_get_error_message(ret, errbuff, sizeof(errbuff));
                fr_strerror_printf("regex evaluation failed with code (%i): %s", ret, errbuff);
 
                return -1;
        }
 
        if (regmatch) regmatch->used = ret;
 
        return 1;
}
 
/** Wrapper around pcre2_substitute
 *
 * @param[in] ctx               to allocate output string in.
 * @param[out] out              Output string with replacements performed.
 * @param[in] max_out           Maximum length of output buffer.  If this is 0 then
 *                              the output length is unlimited.
 * @param[in] preg              The compiled expression.
 * @param[in] flags             that affect matching.
 * @param[in] subject           to perform replacements on.
 * @param[in] subject_len       the length of the subject.
 * @param[in] replacement       replacement string containing substitution
 *                              markers.
 * @param[in] replacement_len   Length of the replacement string.
 * @param[in] regmatch          Array of match pointers.
 * @return
 *      - >= 0 the length of the output string.
 *      - < 0 on error.
 */
int regex_substitute(TALLOC_CTX *ctx, char **out, size_t max_out, regex_t *preg, fr_regex_flags_t const *flags,
                     char const *subject, size_t subject_len,
                     char const *replacement, size_t replacement_len,
                     fr_regmatch_t *regmatch)
{
        int                     ret;
        uint32_t                options = 0;
        size_t                  buff_len, actual_len;
        char                    *buff;
 
#ifndef PCRE2_COPY_MATCHED_SUBJECT
        char                    *our_subject = NULL;
#endif
 
        /*
         *      Thread local initialisation
         */
        if (unlikely(!fr_pcre2_tls) && (fr_pcre2_tls_init() < 0)) return -1;
 
        /*
         *      Internally pcre2_substitute just calls pcre2_match to
         *      generate the match data, so the same hack as the
         *      regex_exec function above is required.
         */
        if (regmatch) {
#ifndef PCRE2_COPY_MATCHED_SUBJECT
                /*
                 *      We have to dup and operate on the duplicate
                 *      of the subject, because pcre2_jit_match and
                 *      pcre2_match store a pointer to the subject
                 *      in the regmatch structure.
                 */
                subject = our_subject = talloc_bstrndup(regmatch, subject, subject_len);
                if (!subject) {
                        fr_strerror_const("Out of memory");
                        return -1;
                }
#else
                /*
                 *      If PCRE2_COPY_MATCHED_SUBJECT is available
                 *      and set as an options flag, pcre2_match will
                 *      strdup the subject string if pcre2_match is
                 *      successful and store a pointer to it in the
                 *      regmatch struct.
                 *
                 *      The lifetime of the string memory will be
                 *      bound to the regmatch struct.  This is more
                 *      efficient that doing it ourselves, as the
                 *      strdup only occurs if the subject matches.
                 */
                options |= PCRE2_COPY_MATCHED_SUBJECT;
#endif
        }
 
        /*
         *      Guess (badly) what the length of the output buffer should be
         */
        actual_len = buff_len = subject_len + 1;        /* +1 for the \0 */
        buff = talloc_array(ctx, char, buff_len);
        if (!buff) {
#ifndef PCRE2_COPY_MATCHED_SUBJECT
                talloc_free(our_subject);
#endif
                fr_strerror_const("Out of memory");
                return -1;
        }
 
        options |= PCRE2_SUBSTITUTE_OVERFLOW_LENGTH;
        if (flags->global) options |= PCRE2_SUBSTITUTE_GLOBAL;
 
again:
        /*
         *      actual_len input value should be the size of the
         *      buffer including space for '\0'.
         *      If input buffer is too small, then actual_len will be set
         *      to the buffer space needed including space for '\0'.
         *      If input buffer is the correct size, then actual_len
         *      will be set to the size of the string written to buff
         *      without the terminating '\0'.
         */
        ret = pcre2_substitute(preg->compiled,
                               (PCRE2_SPTR8)subject, (PCRE2_SIZE)subject_len, 0,
                               options, NULL, fr_pcre2_tls->mcontext,
                               (PCRE2_UCHAR const *)replacement, replacement_len, (PCRE2_UCHAR *)buff, &actual_len);
 
        if (ret < 0) {
                PCRE2_UCHAR errbuff[128];
 
#ifndef PCRE2_COPY_MATCHED_SUBJECT
                talloc_free(our_subject);
#endif
                talloc_free(buff);
 
                if (ret == PCRE2_ERROR_NOMEMORY) {
                        if ((max_out > 0) && (actual_len > max_out)) {
                                fr_strerror_printf("String length with substitutions (%zu) "
                                                    "exceeds max string length (%zu)", actual_len - 1, max_out - 1);
                                return -1;
                        }
 
                        /*
                         *      Check that actual_len != buff_len as that'd be
                         *      an actual error.
                         */
                        if (actual_len == buff_len) {
                                fr_strerror_const("libpcre2 out of memory");
                                return -1;
                        }
                        buff_len = actual_len;  /* The length we get passed back includes the \0 */
                        buff = talloc_array(ctx, char, buff_len);
                        if (!buff) {
                                fr_strerror_const("Out of memory");
                                return -1;
                        }
                        goto again;
                }
 
                if (ret == PCRE2_ERROR_NOMATCH) {
                        if (regmatch) regmatch->used = 0;
                        return 0;
                }
 
                pcre2_get_error_message(ret, errbuff, sizeof(errbuff));
                fr_strerror_printf("regex evaluation failed with code (%i): %s", ret, errbuff);
                return -1;
        }
 
        /*
         *      Trim the replacement buffer to the correct length
         *
         *      buff_len includes \0.
         *      ...and as pcre2_substitute just succeeded actual_len does not include \0.
         */
        if (actual_len < (buff_len - 1)) {
                buff = talloc_bstr_realloc(ctx, buff, actual_len);
                if (!buff) {
                        fr_strerror_const("reallocing pcre2_substitute result buffer failed");
                        return -1;
                }
        }
 
        if (regmatch) regmatch->used = ret;
        *out = buff;
 
        return 1;
}
 
 
/** Returns the number of subcapture groups
 *
 * @return
 *      - >0 The number of subcaptures contained within the pattern
 *      - 0 if the number of subcaptures can't be determined.
 */
uint32_t regex_subcapture_count(regex_t const *preg)
{
        uint32_t count;
 
        if (pcre2_pattern_info(preg->compiled, PCRE2_INFO_CAPTURECOUNT, &count) != 0) {
                fr_strerror_const("Error determining subcapture group count");
                return 0;
        }
 
        return count + 1;
}
 
/** Free libpcre2's matchdata
 *
 * @note Don't call directly, will be called if talloc_free is called on a #regmatch_t.
 */
static int _pcre2_match_data_free(fr_regmatch_t *regmatch)
{
        pcre2_match_data_free(regmatch->match_data);
        return 0;
}
 
/** Allocate vectors to fill with match data
 *
 * @param[in] ctx       to allocate match vectors in.
 * @param[in] count     The number of vectors to allocate.
 * @return
 *      - NULL on error.
 *      - Array of match vectors.
 */
fr_regmatch_t *regex_match_data_alloc(TALLOC_CTX *ctx, uint32_t count)
{
        fr_regmatch_t *regmatch;
 
        /*
         *      Thread local initialisation
         */
        if (unlikely(!fr_pcre2_tls) && (fr_pcre2_tls_init() < 0)) return NULL;
 
        regmatch = talloc(ctx, fr_regmatch_t);
        if (!regmatch) {
        oom:
                fr_strerror_const("Out of memory");
                return NULL;
        }
 
        regmatch->match_data = pcre2_match_data_create(count, fr_pcre2_tls->gcontext);
        if (!regmatch->match_data) {
                talloc_free(regmatch);
                goto oom;
        }
        talloc_set_type(regmatch->match_data, pcre2_match_data);
 
        talloc_set_destructor(regmatch, _pcre2_match_data_free);
 
        return regmatch;
}
 
/*
 *######################################
 *#    FUNCTIONS FOR POSIX-REGEX      #
 *######################################
 */
#  else
/*
 *      Wrapper functions for POSIX like, and extended regular
 *      expressions.  These use the system regex library.
 */
 
/** Free heap allocated regex_t structure
 *
 * Heap allocation of regex_t is needed so regex_compile has the same signature with
 * POSIX or libpcre.
 *
 * @param preg to free.
 */
static int _regex_free(regex_t *preg)
{
        regfree(preg);
 
        return 0;
}
 
/** Binary safe wrapper around regcomp
 *
 * If we have the BSD extensions we don't need to do any special work
 * if we don't have the BSD extensions we need to check to see if the
 * regular expression contains any \0 bytes.
 *
 * If it does we fail and print the appropriate error message.
 *
 * @note Compiled expression must be freed with talloc_free.
 *
 * @param[in] ctx               To allocate memory in.
 * @param[out] out              Where to write out a pointer
 *                              to the structure containing the compiled expression.
 * @param[in] pattern           to compile.
 * @param[in] len               of pattern.
 * @param[in] flags             controlling matching.  May be NULL.
 * @param[in] subcaptures       Whether to compile the regular expression
 *                              to store subcapture data.
 * @param[in] runtime           Whether the compilation is being done at runtime.
 * @return
 *      - >= 1 on success.
 *      - <= 0 on error. Negative value is offset of parse error.
 *      With POSIX regex we only give the correct offset for embedded \0 errors.
 */
ssize_t regex_compile(TALLOC_CTX *ctx, regex_t **out, char const *pattern, size_t len,
                      fr_regex_flags_t const *flags, bool subcaptures, UNUSED bool runtime)
{
        int ret;
        int cflags = REG_EXTENDED;
        regex_t *preg;
 
        if (len == 0) {
                fr_strerror_const("Empty expression");
                return 0;
        }
 
        /*
         *      Options
         */
        if (flags) {
                if (flags->global) {
                        fr_strerror_const("g - Global matching/substitution not supported with posix-regex");
                        return 0;
                }
                if (flags->dot_all) {
                        fr_strerror_const("s - Single line matching is not supported with posix-regex");
                        return 0;
                }
                if (flags->unicode) {
                        fr_strerror_const("u - Unicode matching not supported with posix-regex");
                        return 0;
                }
                if (flags->extended) {
                        fr_strerror_const("x - Whitespace and comments not supported with posix-regex");
                        return 0;
                }
 
                if (flags->ignore_case) cflags |= REG_ICASE;
                if (flags->multiline) cflags |= REG_NEWLINE;
        }
 
 
        if (!subcaptures) cflags |= REG_NOSUB;
 
#ifndef HAVE_REGNCOMP
        {
                char const *p;
 
                p = pattern;
                p += strlen(pattern);
 
                if ((size_t)(p - pattern) != len) {
                        fr_strerror_printf("Found null in pattern at offset %zu.  Pattern unsafe for compilation",
                                           (p - pattern));
                        return -(p - pattern);
                }
 
                preg = talloc_zero(ctx, regex_t);
                if (!preg) return 0;
 
                ret = regcomp(preg, pattern, cflags);
        }
#else
        preg = talloc_zero(ctx, regex_t);
        if (!preg) return 0;
        ret = regncomp(preg, pattern, len, cflags);
#endif
        if (ret != 0) {
                char errbuf[128];
 
                regerror(ret, preg, errbuf, sizeof(errbuf));
                fr_strerror_printf("%s", errbuf);
 
                talloc_free(preg);
 
                return 0;       /* POSIX expressions don't give us the failure offset */
        }
 
        talloc_set_destructor(preg, _regex_free);
        *out = preg;
 
        return len;
}
 
/** Binary safe wrapper around regexec
 *
 * If we have the BSD extensions we don't need to do any special work
 * If we don't have the BSD extensions we need to check to see if the
 * value to be compared contains any \0 bytes.
 *
 * If it does, we fail and print the appropriate error message.
 *
 * @param[in] preg      The compiled expression.
 * @param[in] subject   to match.
 * @param[in] regmatch  Match result structure.
 * @return
 *      - -1 on failure.
 *      - 0 on no match.
 *      - 1 on match.
 */
int regex_exec(regex_t *preg, char const *subject, size_t len, fr_regmatch_t *regmatch)
{
        int     ret;
        size_t  matches;
 
        /*
         *      Disable capturing
         */
        if (!regmatch) {
                matches = 0;
        } else {
                matches = regmatch->allocd;
 
                /*
                 *      Reset the match result structure
                 */
                memset(regmatch->match_data, 0, sizeof(regmatch->match_data[0]) * matches);
                regmatch->used = 0;
        }
 
#ifndef HAVE_REGNEXEC
        {
                char const *p;
 
                p = subject;
                p += strlen(subject);
 
                if ((size_t)(p - subject) != len) {
                        fr_strerror_printf("Found null in subject at offset %zu.  String unsafe for evaluation",
                                           (p - subject));
                        if (regmatch) regmatch->used = 0;
                        return -1;
                }
                ret = regexec(preg, subject, matches, regmatch ? regmatch->match_data : NULL, 0);
        }
#else
        ret = regnexec(preg, subject, len, matches, regmatch ? regmatch->match_data : NULL, 0);
#endif
        if (ret != 0) {
                if (ret != REG_NOMATCH) {
                        char errbuf[128];
 
                        regerror(ret, preg, errbuf, sizeof(errbuf));
 
                        fr_strerror_printf("regex evaluation failed: %s", errbuf);
                        return -1;
                }
                return 0;
        }
 
        /*
         *      Update regmatch->count to be the maximum number of
         *      groups that *could* have been populated as we don't
         *      have the number of matches.
         */
        if (regmatch) {
                regmatch->used = preg->re_nsub + 1;
 
                if (regmatch->subject) talloc_const_free(regmatch->subject);
                regmatch->subject = talloc_bstrndup(regmatch, subject, len);
                if (!regmatch->subject) {
                        fr_strerror_const("Out of memory");
                        return -1;
                }
        }
        return 1;
}
 
/** Returns the number of subcapture groups
 *
 * @return
 *      - 0 we can't determine this for POSIX regular expressions.
 */
uint32_t regex_subcapture_count(UNUSED regex_t const *preg)
{
        return 0;
}
#  endif
 
#  if defined(HAVE_REGEX_POSIX)
/** Allocate vectors to fill with match data
 *
 * @param[in] ctx       to allocate match vectors in.
 * @param[in] count     The number of vectors to allocate.
 * @return
 *      - NULL on error.
 *      - Array of match vectors.
 */
fr_regmatch_t *regex_match_data_alloc(TALLOC_CTX *ctx, uint32_t count)
{
        fr_regmatch_t *regmatch;
 
        /*
         *      Pre-allocate space for the match structure
         *      and for a 128b subject string.
         */
        regmatch = talloc_zero_pooled_object(ctx, fr_regmatch_t, 2, (sizeof(regmatch_t) * count) + 128);
        if (unlikely(!regmatch)) {
        error:
                fr_strerror_const("Out of memory");
                talloc_free(regmatch);
                return NULL;
        }
        regmatch->match_data = talloc_array(regmatch, regmatch_t, count);
        if (unlikely(!regmatch->match_data)) goto error;
 
        regmatch->allocd = count;
        regmatch->used = 0;
        regmatch->subject = NULL;
 
        return regmatch;
}
#  endif
 
/*
 *########################################
 *#         UNIVERSAL FUNCTIONS          #
 *########################################
 */
 
/** Parse a string containing one or more regex flags
 *
 * @param[out] err              May be NULL. If not NULL will be set to:
 *                              - 0 on success.
 *                              - -1 on unknown flag.
 *                              - -2 on duplicate.
 * @param[out] out              Flag structure to populate.  Must be initialised to zero
 *                              if this is the first call to regex_flags_parse.
 * @param[in] in                Flag string to parse.
 * @param[in] terminals         Terminal characters. If parsing ends before the buffer
 *                              is exhausted, and is pointing to one of these chars
 *                              it's not considered an error.
 * @param[in] err_on_dup        Error if the flag is already set.
 * @return
 *      - > 0 on success.  The number of flag bytes parsed.
 *      - <= 0 on failure.  Negative offset of first unrecognised flag.
 */
fr_slen_t regex_flags_parse(int *err, fr_regex_flags_t *out, fr_sbuff_t *in,
                            fr_sbuff_term_t const *terminals, bool err_on_dup)
{
        fr_sbuff_t      our_in = FR_SBUFF(in);
 
        if (err) *err = 0;
 
        while (fr_sbuff_extend(&our_in)) {
                switch (*our_in.p) {
#define DO_REGEX_FLAG(_f, _c) \
                case _c: \
                        if (err_on_dup && out->_f) { \
                                fr_strerror_printf("Duplicate regex flag '%c'", *our_in.p); \
                                if (err) *err = -2; \
                                FR_SBUFF_ERROR_RETURN(&our_in); \
                        } \
                        out->_f = 1; \
                        break
 
                DO_REGEX_FLAG(global, 'g');
                DO_REGEX_FLAG(ignore_case, 'i');
                DO_REGEX_FLAG(multiline, 'm');
                DO_REGEX_FLAG(dot_all, 's');
                DO_REGEX_FLAG(unicode, 'u');
                DO_REGEX_FLAG(extended, 'x');
#undef DO_REGEX_FLAG
 
                default:
                        if (fr_sbuff_is_terminal(&our_in, terminals)) FR_SBUFF_SET_RETURN(in, &our_in);
 
                        fr_strerror_printf("Unsupported regex flag '%c'", *our_in.p);
                        if (err) *err = -1;
                        FR_SBUFF_ERROR_RETURN(&our_in);
                }
                fr_sbuff_advance(&our_in, 1);
        }
        FR_SBUFF_SET_RETURN(in, &our_in);
}
 
/** Print the flags
 *
 * @param[out] sbuff    where to write flags.
 * @param[in] flags     to print.
 * @return
 *      - The number of bytes written to the out buffer.
 *      - A number >= outlen if truncation has occurred.
 */
ssize_t regex_flags_print(fr_sbuff_t *sbuff, fr_regex_flags_t const *flags)
{
        fr_sbuff_t our_sbuff = FR_SBUFF(sbuff);
 
#define DO_REGEX_FLAG(_f, _c) \
        if (flags->_f) FR_SBUFF_IN_CHAR_RETURN(&our_sbuff, _c)
 
        DO_REGEX_FLAG(global, 'g');
        DO_REGEX_FLAG(ignore_case, 'i');
        DO_REGEX_FLAG(multiline, 'm');
        DO_REGEX_FLAG(dot_all, 's');
        DO_REGEX_FLAG(unicode, 'u');
        DO_REGEX_FLAG(extended, 'x');
#undef DO_REGEX_FLAG
 
        FR_SBUFF_SET_RETURN(sbuff, &our_sbuff);
}
#endif
 
/** Compare two boxes using an operator
 *
 *  @todo - allow /foo/i on the RHS
 *
 *  However, this involves allocating intermediate sbuffs for the
 *  unescaped RHS, and all kinds of extra work.  It's not overly hard,
 *  but it's something we wish to avoid for now.
 *
 * @param[in] op to use in comparison. MUST be T_OP_REG_EQ or T_OP_REG_NE
 * @param[in] a Value to compare,  MUST be FR_TYPE_STRING
 * @param[in] b uncompiled regex as FR_TYPE_STRING
 * @return
 *      - 1 if true
 *      - 0 if false
 *      - -1 on failure.
 */
int fr_regex_cmp_op(fr_token_t op, fr_value_box_t const *a, fr_value_box_t const *b)
{
        int rcode;
        TALLOC_CTX *ctx = NULL;
        size_t lhs_len;
        char const *lhs;
        regex_t *regex = NULL;
 
        if (!((op == T_OP_REG_EQ) || (op == T_OP_REG_NE))) {
                fr_strerror_const("Invalid operator for regex comparison");
                return -1;
        }
 
        if (b->type != FR_TYPE_STRING) {
                fr_strerror_const("RHS must be regular expression");
                return -1;
        }
 
        ctx = talloc_init_const("regex_cmp_op");
        if (!ctx) return -1;
 
        if ((a->type != FR_TYPE_STRING) && (a->type != FR_TYPE_OCTETS)) {
                fr_slen_t slen;
                char *p;
 
                slen = fr_value_box_aprint(ctx, &p, a, NULL); /* no escaping */
                if (slen < 0) return slen;
 
                lhs = p;
                lhs_len = slen;
 
        } else {
                lhs = a->vb_strvalue;
                lhs_len = a->vb_length;
        }
 
        if (regex_compile(ctx, &regex, b->vb_strvalue, b->vb_length, NULL, false, true) < 0) {
                talloc_free(ctx);
                return -1;
        }
 
#ifdef STATIC_ANALYZER
        if (!regex) {
                talloc_free(ctx);
                return -1;
        }
#endif
 
        rcode = regex_exec(regex, lhs, lhs_len, NULL);
        talloc_free(ctx);
        if (rcode < 0) return rcode;
 
        /*
         *      Invert the sense of the rcode for !~
         */
        if (op == T_OP_REG_NE) rcode = (rcode == 0);
 
        return rcode;
}