pem: add passphrase-protected PEM file support for libgcrypt and wincng

Since they use our own PEM parser which did not support encrypted
PEM files, trying to use such files on these backends failed.
Fix that by augmenting the PEM parser to support encrypted PEM files.

src/crypt.c

@@ -53,6 +53,7 @@ crypt_none_crypt(LIBSSH2_SESSION * session, unsigned char *buf,
 
 static const LIBSSH2_CRYPT_METHOD libssh2_crypt_method_none = {
     "none",
+    "DEK-Info: NONE"
     8,                     /* blocksize (SSH2 defines minimum blocksize as 8) */
     0,                     /* iv_len */
     0,                     /* secret_len */
@@ -119,6 +120,7 @@ crypt_dtor(LIBSSH2_SESSION * session, void **abstract)
 #if LIBSSH2_AES_CTR
 static const LIBSSH2_CRYPT_METHOD libssh2_crypt_method_aes128_ctr = {
     "aes128-ctr",
+    "",
     16,                         /* blocksize */
     16,                         /* initial value length */
     16,                         /* secret length -- 16*8 == 128bit */
@@ -131,6 +133,7 @@ static const LIBSSH2_CRYPT_METHOD libssh2_crypt_method_aes128_ctr = {
 
 static const LIBSSH2_CRYPT_METHOD libssh2_crypt_method_aes192_ctr = {
     "aes192-ctr",
+    "",
     16,                         /* blocksize */
     16,                         /* initial value length */
     24,                         /* secret length -- 24*8 == 192bit */
@@ -143,6 +146,7 @@ static const LIBSSH2_CRYPT_METHOD libssh2_crypt_method_aes192_ctr = {
 
 static const LIBSSH2_CRYPT_METHOD libssh2_crypt_method_aes256_ctr = {
     "aes256-ctr",
+    "",
     16,                         /* blocksize */
     16,                         /* initial value length */
     32,                         /* secret length -- 32*8 == 256bit */
@@ -157,6 +161,7 @@ static const LIBSSH2_CRYPT_METHOD libssh2_crypt_method_aes256_ctr = {
 #if LIBSSH2_AES
 static const LIBSSH2_CRYPT_METHOD libssh2_crypt_method_aes128_cbc = {
     "aes128-cbc",
+    "DEK-Info: AES-128-CBC",
     16,                         /* blocksize */
     16,                         /* initial value length */
     16,                         /* secret length -- 16*8 == 128bit */
@@ -169,6 +174,7 @@ static const LIBSSH2_CRYPT_METHOD libssh2_crypt_method_aes128_cbc = {
 
 static const LIBSSH2_CRYPT_METHOD libssh2_crypt_method_aes192_cbc = {
     "aes192-cbc",
+    "DEK-Info: AES-192-CBC",
     16,                         /* blocksize */
     16,                         /* initial value length */
     24,                         /* secret length -- 24*8 == 192bit */
@@ -181,6 +187,7 @@ static const LIBSSH2_CRYPT_METHOD libssh2_crypt_method_aes192_cbc = {
 
 static const LIBSSH2_CRYPT_METHOD libssh2_crypt_method_aes256_cbc = {
     "aes256-cbc",
+    "DEK-Info: AES-256-CBC",
     16,                         /* blocksize */
     16,                         /* initial value length */
     32,                         /* secret length -- 32*8 == 256bit */
@@ -195,6 +202,7 @@ static const LIBSSH2_CRYPT_METHOD libssh2_crypt_method_aes256_cbc = {
 static const LIBSSH2_CRYPT_METHOD
     libssh2_crypt_method_rijndael_cbc_lysator_liu_se = {
     "rijndael-cbc@lysator.liu.se",
+    "DEK-Info: AES-256-CBC",
     16,                         /* blocksize */
     16,                         /* initial value length */
     32,                         /* secret length -- 32*8 == 256bit */
@@ -209,6 +217,7 @@ static const LIBSSH2_CRYPT_METHOD
 #if LIBSSH2_BLOWFISH
 static const LIBSSH2_CRYPT_METHOD libssh2_crypt_method_blowfish_cbc = {
     "blowfish-cbc",
+    "",
     8,                          /* blocksize */
     8,                          /* initial value length */
     16,                         /* secret length */
@@ -223,6 +232,7 @@ static const LIBSSH2_CRYPT_METHOD libssh2_crypt_method_blowfish_cbc = {
 #if LIBSSH2_RC4
 static const LIBSSH2_CRYPT_METHOD libssh2_crypt_method_arcfour = {
     "arcfour",
+    "DEK-Info: RC4",
     8,                          /* blocksize */
     8,                          /* initial value length */
     16,                         /* secret length */
@@ -258,6 +268,7 @@ crypt_init_arcfour128(LIBSSH2_SESSION * session,
 
 static const LIBSSH2_CRYPT_METHOD libssh2_crypt_method_arcfour128 = {
     "arcfour128",
+    "",
     8,                          /* blocksize */
     8,                          /* initial value length */
     16,                         /* secret length */
@@ -272,6 +283,7 @@ static const LIBSSH2_CRYPT_METHOD libssh2_crypt_method_arcfour128 = {
 #if LIBSSH2_CAST
 static const LIBSSH2_CRYPT_METHOD libssh2_crypt_method_cast128_cbc = {
     "cast128-cbc",
+    "",
     8,                          /* blocksize */
     8,                          /* initial value length */
     16,                         /* secret length */
@@ -286,6 +298,7 @@ static const LIBSSH2_CRYPT_METHOD libssh2_crypt_method_cast128_cbc = {
 #if LIBSSH2_3DES
 static const LIBSSH2_CRYPT_METHOD libssh2_crypt_method_3des_cbc = {
     "3des-cbc",
+    "DEK-Info: DES-EDE3-CBC",
     8,                          /* blocksize */
     8,                          /* initial value length */
     24,                         /* secret length */

src/libgcrypt.c

@@ -172,8 +172,6 @@ _libssh2_rsa_new_private(libssh2_rsa_ctx ** rsa,
     unsigned char *n, *e, *d, *p, *q, *e1, *e2, *coeff;
     unsigned int nlen, elen, dlen, plen, qlen, e1len, e2len, coefflen;
 
-    (void) passphrase;
-
     fp = fopen(filename, "r");
     if (!fp) {
         return -1;
@@ -182,6 +180,7 @@ _libssh2_rsa_new_private(libssh2_rsa_ctx ** rsa,
     ret = _libssh2_pem_parse(session,
                              "-----BEGIN RSA PRIVATE KEY-----",
                              "-----END RSA PRIVATE KEY-----",
+                             passphrase,
                              fp, &data, &datalen);
     fclose(fp);
     if (ret) {
@@ -285,8 +284,6 @@ _libssh2_dsa_new_private(libssh2_dsa_ctx ** dsa,
     unsigned char *p, *q, *g, *y, *x;
     unsigned int plen, qlen, glen, ylen, xlen;
 
-    (void) passphrase;
-
     fp = fopen(filename, "r");
     if (!fp) {
         return -1;
@@ -295,6 +292,7 @@ _libssh2_dsa_new_private(libssh2_dsa_ctx ** dsa,
     ret = _libssh2_pem_parse(session,
                              "-----BEGIN DSA PRIVATE KEY-----",
                              "-----END DSA PRIVATE KEY-----",
+                             passphrase,
                              fp, &data, &datalen);
     fclose(fp);
     if (ret) {

src/libssh2_priv.h

@@ -884,6 +884,7 @@ struct _LIBSSH2_HOSTKEY_METHOD
 struct _LIBSSH2_CRYPT_METHOD
 {
     const char *name;
+    const char *pem_annotation;
 
     int blocksize;
 
@@ -1041,6 +1042,7 @@ const LIBSSH2_HOSTKEY_METHOD **libssh2_hostkey_methods(void);
 int _libssh2_pem_parse(LIBSSH2_SESSION * session,
                        const char *headerbegin,
                        const char *headerend,
+                       const unsigned char *passphrase,
                        FILE * fp, unsigned char **data, unsigned int *datalen);
 int _libssh2_pem_parse_memory(LIBSSH2_SESSION * session,
                               const char *headerbegin,

src/os400qc3.c

@@ -2005,6 +2005,7 @@ try_pem_load(LIBSSH2_SESSION *session, FILE *fp,
     fseek(fp, 0L, SEEK_SET);
     for (;;) {
         ret = _libssh2_pem_parse(session, header, trailer,
+                                 NULL,
                                  fp, &data, &datalen);
 
         if (!ret) {

src/pem.c

@@ -37,6 +37,7 @@
  */
 
 #include "libssh2_priv.h"
+#include <assert.h>
 
 static int
 readline(char *line, int line_size, FILE * fp)
@@ -96,16 +97,26 @@ readline_memory(char *line, size_t line_size,
 
 #define LINE_SIZE 128
 
+const char *crypt_annotation = "Proc-Type: 4,ENCRYPTED";
+
+static unsigned char hex_decode(char digit)
+{
+    return (digit >= 'A') ? 0xA + (digit - 'A') : (digit - '0');
+}
+
 int
 _libssh2_pem_parse(LIBSSH2_SESSION * session,
                    const char *headerbegin,
                    const char *headerend,
+                   const unsigned char *passphrase,
                    FILE * fp, unsigned char **data, unsigned int *datalen)
 {
     char line[LINE_SIZE];
+    unsigned char iv[LINE_SIZE];
     char *b64data = NULL;
     unsigned int b64datalen = 0;
     int ret;
+    const LIBSSH2_CRYPT_METHOD *method = NULL;
 
     do {
         *line = '\0';
@@ -116,7 +127,45 @@ _libssh2_pem_parse(LIBSSH2_SESSION * session,
     }
     while (strcmp(line, headerbegin) != 0);
 
-    *line = '\0';
+    if (readline(line, LINE_SIZE, fp)) {
+        return -1;
+    }
+
+    if (passphrase &&
+            memcmp(line, crypt_annotation, strlen(crypt_annotation)) == 0) {
+        const LIBSSH2_CRYPT_METHOD **all_methods, *cur_method;
+        int i;
+
+        if (readline(line, LINE_SIZE, fp)) {
+            ret = -1;
+            goto out;
+        }
+        all_methods = libssh2_crypt_methods();
+        while ((cur_method = *all_methods++)) {
+            if (*cur_method->pem_annotation &&
+                    memcmp(line, cur_method->pem_annotation, strlen(cur_method->pem_annotation)) == 0) {
+                method = cur_method;
+                memcpy(iv, line+strlen(method->pem_annotation)+1, 2*method->iv_len);
+            }
+        }
+
+        /* None of the available crypt methods were able to decrypt this key */
+        if (method == NULL)
+            return -1;
+
+        /* Decode IV from hex */
+        for (i = 0; i < method->iv_len; ++i)
+        {
+            iv[i]  = hex_decode(iv[2*i]) << 4;
+            iv[i] |= hex_decode(iv[2*i+1]);
+        }
+
+        /* skip to the next line */
+        if (readline(line, LINE_SIZE, fp)) {
+            ret = -1;
+            goto out;
+        }
+    }
 
     do {
         if (*line) {
@@ -152,6 +201,72 @@ _libssh2_pem_parse(LIBSSH2_SESSION * session,
         goto out;
     }
 
+    if (method) {
+        /* Set up decryption */
+        int free_iv = 0, free_secret = 0, len_decrypted = 0, padding = 0;
+        int blocksize = method->blocksize;
+        void *abstract;
+        unsigned char secret[2*MD5_DIGEST_LENGTH];
+        libssh2_md5_ctx fingerprint_ctx;
+
+        /* Perform key derivation (PBKDF1/MD5) */
+        if (!libssh2_md5_init(&fingerprint_ctx)) {
+            ret = -1;
+            goto out;
+        }
+        libssh2_md5_update(fingerprint_ctx, passphrase, strlen((char*)passphrase));
+        libssh2_md5_update(fingerprint_ctx, iv, 8);
+        libssh2_md5_final(fingerprint_ctx, secret);
+        if (method->secret_len > MD5_DIGEST_LENGTH) {
+            if (!libssh2_md5_init(&fingerprint_ctx)) {
+                ret = -1;
+                goto out;
+            }
+            libssh2_md5_update(fingerprint_ctx, secret, MD5_DIGEST_LENGTH);
+            libssh2_md5_update(fingerprint_ctx, passphrase, strlen((char*)passphrase));
+            libssh2_md5_update(fingerprint_ctx, iv, 8);
+            libssh2_md5_final(fingerprint_ctx, secret + MD5_DIGEST_LENGTH);
+        }
+
+        /* Initialize the decryption */
+        if (method->init(session, method, iv, &free_iv, secret,
+                 &free_secret, 0, &abstract)) {
+            memset((char*)secret, 0, sizeof(secret));
+            LIBSSH2_FREE(session, data);
+            ret = -1;
+            goto out;
+        }
+
+        if (free_secret) {
+            memset((char*)secret, 0, sizeof(secret));
+        }
+
+        /* Do the actual decryption */
+        assert((*datalen % blocksize) == 0);
+
+        while (len_decrypted <= *datalen - blocksize) {
+            if (method->crypt(session, *data + len_decrypted, blocksize,
+                                             &abstract)) {
+                ret = LIBSSH2_ERROR_DECRYPT;
+                method->dtor(session, &abstract);
+                memset(*data, 0, *datalen);
+                LIBSSH2_FREE(session, *data);
+                goto out;
+            }
+
+            len_decrypted += blocksize;
+        }
+
+        /* Account for padding */
+        padding = (*data)[*datalen - 1];
+        memset(&(*data)[*datalen-padding],0,padding);
+        *datalen -= padding;
+
+        /* Clean up */
+        memset((char*)secret, 0, sizeof(secret));
+        method->dtor(session, &abstract);
+    }
+
     ret = 0;
   out:
     if (b64data) {

src/wincng.c

@@ -549,14 +549,13 @@ _libssh2_wincng_load_pem(LIBSSH2_SESSION *session,
     FILE *fp;
     int ret;
 
-    (void)passphrase;
-
     fp = fopen(filename, "r");
     if (!fp) {
         return -1;
     }
 
     ret = _libssh2_pem_parse(session, headerbegin, headerend,
+                             passphrase,
                              fp, data, datalen);
 
     fclose(fp);